Chemistry

Soluble and Insoluble Salts

- All sodium, potassium and ammonium salts are soluble. All nitrates are soluble. (All SPAN salts are soluble) - All chlorides, bromides and iodides are soluble except for silver and lead (II) chloride, bromide and iodide - All sulfates are soluble except for lead(II), barium and calcium sulfate. (All sulfates are soluble except for Peanut Butter Carrot) - All carbonates are insoluble except for sodium, potassium and ammonium carbonate. - All hydroxides are insoluble except sodium, potassium, ammonium, calcium and barium hydroxides - All oxides are insoluble expect sodium, potassium and ammonium oxide

Drying a Gas

- Concentrated sulfuric acid is used to dry most gases, including chlorine and hydrogen chloride. However, it cannot be used to dry ammonia because it reacts with ammonia - Quicklime (calcium oxide) is used to dry ammonia - Fused calcium chloride (anhydrous) can be used to dry most gases

What are the effects of impurities on boiling point?

- Impurities increases the boiling point of a liquid. The greater the amount of impurities, the higher the boiling point - Impurities cause boiling to take place over a range of temperatures

What are the effects of impurities on melting point?

- Impurities lower the melting point of a solid. The greater the amount of impurities, the lower the melting point. - Impurities cause melting to take place over a range of temperatures.

Uses of bases and alkalis

- Magnesium oxide is used as antacid for relieving gastric pain - Sodium hydroxide and potassium hydroxide are used in the preparation of soap - Calcium hydroxide (slaked lime or limewater) and calcium oxide (quicklime) are used to reduce acidity in the soil - Ammonia solution is used to make fertilisers

What are the uses of sulfuric acid?

- Manufacture of fertilisers. Sulfuric acid is an important starting material for the production of ammonium sulfate and superphosphate, the active ingredients in fertilisers. - Manufacture of detergents Concentrated sulfuric acid is used in the manufacture of detergents to convert hydrocarbons into organic acids. The organic acids are then reacted with sodium hydroxide to produce the detergent. - As battery acid in cars Dilute sulfuric acid is used in car batteries. It reacts with lead plates and lead (IV) oxide plates in the battery to generate electrical energy, which is used to get the car running.

Properties of Acids

1. Acids have a sour taste 2. Acids dissolve in water to form solutions which conduct electricity 3. Acids turn blue litmus paper red 4. Acids react with reactive metals to form a salt and hydrogen gas (copper and silver are considered unreactive) [Take note that initial reaction may produce insoluble coating that prevents further reaction] 5. Acids react with carbonates to form a salt, water and carbon dioxide gas. 6. Acids react with metal oxides and hydroxides to form a salt and water only. (acid + base/alkali)

Addition Reaction of Alkenes

1. Addition of hydrogen (hydrogenation) - At 200°C and in the presence of a catalyst such as nickel, alkenes can react with hydrogen to form alkanes. 2. Addition of bromine (Bromination) - A solution of bromine is reddish-brown. If an alkene is added, the reddish-brown colour disappears immediately and a colourless liquid is formed. 3. Addition of steam (hydration) - Alkenes can react with steam to produce alcohols. The conditions required are a temperature of 300°C and a pressure of 60atm. The reactions also requires a catalyst. (Phosphoric(V) acid, H3PO4) 4. Addition polymerisation

Properties of Alkalis

1. Alkalis have a bitter taste and feel soapy 2. Alkalis turn red litmus paper blue 3. Alkalis react with acids to form a salt and water only. 4. Alkalis, when heated with ammonium salts, give off ammonia gas 5. Alkalis react with a solution of one metal salt to give another metal salt and metal hydroxide (displacement reaction?)

Effects of Air Pollutants

1. Carbon dioxide in excess - Contributes to the greenhouse effect as it is a greenhouse gas 2. Carbon monoxide - Reacts with haemoglobin in the blood to form carboxyhemoglobin which reduces the ability of the haemoglobin to transport oxygen around the body - Causes headaches, fatigue, breathing difficulties and even death 3. Sulfur dioxide, oxides of nitrogen - Is an acidic oxide and will react with water in the atmosphere to form acid rain which corrodes buildings and harms aquatic plant and animal life. - Irritates the eyes and lungs and causes breathing difficulties - High levels lead to inflammation of the lungs 4. Unburnt hydrocarbons - Causes cancer - Reacts with oxides of nitrogen to form ozone 5. Methane - Greenhouse gas which contributes to global warming 6. Ozone - Forms photochemical smog, which irritates the eyes and lungs and causes breathing difficulties - Damages crops

Common Air Pollutants

1. Carbon monoxide - Comes from incomplete combustion of petrol 2. Sulfur dioxide - Burning of fossil fuels such as coal, crude oil and natural gases in motor vehicles, power stations and factories. - Produced in large quantities during volcanic eruptions 3. Oxides of Nitrogen - In a car engine or chemical factory, nitrogen combines with oxygen to form nitrogen monoxide. Nitrogen monoxide reacts with oxygen to form nitrogen dioxide. - Heat energy released by lightning causes nitrogen and oxygen to react to form oxides like nitrogen monoxide and nitrogen dioxide. 4. Unburnt Hydrocarbons - Vehicle exhaust fumes - Chemical plants 5. Methane - Decay of plant and animal matter 6. Ozone - Reaction of nitrogen dioxide and unburnt hydrocarbons in the presence of sunlight

Chemical Properties of Alkenes

1. Combustion 2. Addition Reactions

Chemical Properties of Alcohols

1. Combustion 2. Oxidation - An alcohol undergoes oxidation when it is heated with an oxidising agent such as acidified potassium manganate (VII). A carboxylic acid and water are formed. E.g. CH3CH2OH(aq) + 2[O] -heat-> CH3COOH(aq) +H2O(l) [O] comes from an oxidising agent

Chemical Reactions that Alkanes can undergo

1. Combustion 2. Substitution reactions: Alkanes with halogens can undergo substitution reactions in the presence of UV light

Rules for selective discharge of Anions

1. Concentration An anion in higher concentration is more readily discharged. 2. Ease of discharge increases as we go down: Chloride ion Bromide ion Iodide ion Hydroxide ion (Sulfate and nitrate ions are never discharged during electrolysis) 4OH- (aq) --> O2 (g) + 2H2O (l) + 4e-

Factors Affecting the Speed of Reaction

1. Concentration 2. Pressure of a gaseous reactant 3. Surface area to volume ratio 4. Temperature 5. Catalyst

How do you obtain pure copper (II) sulfate crystals by crystallisation?

1. Dissolve the impure copper (II) sulfate crystals in water. 2. Filter to remove any insoluble impurities. Collect the filtrate. This is copper (II) sulfate solution. 3. Heat the copper (II) sulfate solution until it is saturated (Dip clean glass rod into solution and remove. Small crystals should form on the rod as the solution cools) 4. When the solution is saturated, leave it to cool and crystallise. 5. Filter to collect the crystals. Wash the crystals with a little cold distilled water to remove impurities. Dry the crystals between a few sheets of filter paper.

Properties of Gases

1. Does not have a fixed shape 2. Does not have a fixed volume 3. Can be compressed

Properties of Liquids

1. Does not have a fixed shape 2. Has a fixed volume 3. Cannot be compressed

Rules for selective discharge of cations

1. Ease of discharge increases down the reactivity series 2H+(aq) + 2e- --> H2(g)

Industrial Uses of Electrolysis

1. Electroplating 2. Electrolytic Purification of Copper

What causes energy changes in chemical reactions?

1. Energy absorbed in bond breaking 2. Energy released in bond making

What happens to the particles of a liquid that is cooled until it freezes?

1. Energy is given out by the particles of the liquid. The particles lose kinetic energy and begin to move more slowly. 2. When the temperature is low enough, the particles no longer have enough energy to move freely. The particles start to settle into fixed positions 3. All the particles have settled into fixed positions. The substance is now a solid. The particles can only vibrate about their fixed positions

Uses of Esters

1. Esters are used in the preparation of artificial food flavourings due to their sweet fruity smells. 2. Esters with small molecular sizes are volatile liquids and are used as solvents for cosmetics, perfumes and glues. 3. Soap when animal fats or vegetable oils are boiled with sodium hydroxide.

How do Catalytic Converters help remove pollutants in vehicle exhaust gases?

1. Exhaust gases containing carbon monoxide, oxides of nitrogen and unburnt hydrocarbons are passed over the platinum and rhodium catalysts in a catalytic converter. 2. The harmful pollutants are converted into harmless substances by redox reactions: - Carbon monoxide is oxidised to carbon dioxide: 2CO(g) + O2(g) --> 2CO2(g) - Oxides of nitrogen are reduced to nitrogen gas: 2NO(g) + 2CO(g) --> N2(g) + 2CO2(g) - Unburnt hydrocarbons such as octane are oxidised to carbon dioxide and water: 2C8H18(l) + 25O2(g) --> 16CO2(g) + 18H2O(g)

Properties of Solids

1. Have fixed shapes 2. Have fixed volumes 3. Cannot be compressed

What happens to the particles of a liquid that is heated until it boils?

1. Heat energy is absorbed by the particles of the liquid. The heat energy is converted into kinetic energy. The particles start to move faster as the temperature rises. 2. When the temperature is high enough, the particles have enough energy to overcome the forces of attraction holding them together. 3. The particles are now spread far apart. The substance is now a gas. The particles can move about in any direction

What happens to the particles of a solid that is heated until it melts?

1. Heat energy is absorbed by the particles of the solid. The heat energy is converted into kinetic energy. The particles start to vibrate faster about their fixed positions. 2. When the temperature is high enough, the vibrations of the particles become sufficient to overcome the forces of attraction between them. The particles begin to break away from their fixed positions. 3. The particles are no longer in their fixed positions. The substance is now a liquid. The particles can move freely throughout the liquid

Uses of Ethanol

1. In alcoholic drinks 2. As a solvent (e.g. in paints, varnishes, deodorants, perfumes, colognes and after-shave lotions) 3. As a fuel in cars or for cooking

Method for Preparing a Salt

1. Is the desired salt soluble in water? If yes go to 3. if no go to 2. 2. Method 3: Precipitation - Solution containing cation of salt ( ____ nitrate) + solution containing anion of salt (sodium ____) - Filter the mixture to obtain salt crystals 3. Are both the starting materials soluble in water? If yes go to 4. if no go to 5. 4. Method 2: Titration - Acid + alkali - Acid + soluble carbonate - Crystallise the salt solution - Filter to obtain the salt crystals 5. Reaction of Acid with an Insoluble Substance - Acid + excess metal - Acid + excess insoluble base - Acid + excess insoluble carbonate - Filter the mixture - Collect the filtrate - Crystallise the filtrate - Filter to obtain salt crystals and wash with cold water then pat dry with filter paper

Types of Steel and their Uses

1. Low Carbon Steel - Low percentage of carbon - Relatively soft and therefore easily shaped - Bodies of motorcars, building structures 2. High Carbon Steel - Higher percentage of carbon - Is relatively hard and brittle - Springs, knife blades, masonry drills 3. Stainless Steel - Composed of chromium, nickel, iron and carbon - More resistant to corrosion - Cutlery, surgical instruments

Physical Properties of Ionic Compounds

1. Most ionic compounds have high melting and boiling points In an ionic compound, the ions are bonded together by strong ionic bonds. A large amount of energy is required to break the bonds between ions. Hence many ionic compounds have high melting and boiling points. 2. Ionic compounds are usually soluble in water and insoluble in organic solvents. Water molecules are attracted to ions, weakening the electrostatic forces between the ions. Hence the ions are pulled from the lattice structure and the compound dissolves to form an aqueous solution. However organic solvents have no water so this does not happen 3. Ionic compounds conduct electricity when molten or in aqueous solution. When an ionic compound is molten or dissolved in water to form an aqueous solution, the cations and anions are free to move and can act as mobile charged particles to conduct electricity

Fractional Distillation of Petroleum

1. Petroleum is heated and turned into a vapour. The vapour is passed into a fractioning column 2. As the hot vapour rises, it begins to cool and condense. Lighter fractions have lower boiling points. They are collected at the top of the fractioning columns as gases. Heavier fractions have higher boiling points and are collected at lower sections of the fractioning column

Chemical Properties of Carboxylic Acids

1. Reaction with reactive metals (just acid-metal reactions lmao) to produce salt and hydrogen gas 2CH3COOH(aq) + Mg(s) --> (CH3COO)2Mg(aq) + H2(g) [Magnesium ethanoate produced] 2. Reaction with carbonates to give salt, carbon dioxide and water 3. Reaction with bases to give salt and water 4. Reaction with alcohols to produce esters and water

What are the physical properties of substances with giant molecular structures?

1. Substances with giant molecular structures have very high melting and boiling points A giant molecular structure consists of a large number of atoms that are held together by strong covalent bonds. To melt of boil the substance, these strong bonds must be broke, this requires a large amount of energy. Hence they have high melting and boiling points 2. Substances with giant molecular structures do not conduct electricity (except graphite) In giant molecular substances (except graphite), all the other electrons of the atoms are used to form covalent bonds. Thus there are no free electrons that move through the structure to conduct electricity. And does not contain ions. Therefore no mobile charged particles to act as charge carriers for the conduction of electricity 3. Insoluble in both water and organic solvents

Properties of substances with simple molecular structures

1. Substances with simple molecular substances have low melting and boiling points. Between simple molecules, there are only weak van der Waals' forces of attraction holding them together. Little energy is required to overcome the weak van der Waals' forces of attraction. Hence simple molecular substances have low melting and boiling points 2. Substances with simple molecular structures are usually insoluble in water and soluble in organic solvents 3. Most substances with simple molecular structures do not conduct electricity whether in the solid, liquid or gaseous state. This is because simple molecular substances do not have any free-moving ions or electrons to conduct electricity.

Extraction of Iron from Haematite

1. The carbon in coke burns in a blast of hot air to produce carbon dioxide. This reactions produces a lot of heat. C(s) + O2(g) --> CO2(g) 2. As the carbon dioxide rises up the furnace, it reacts with more coke to form carbon monoxide. C(s) + CO2(g) --> 2CO(g) 3. The carbon monoxide reduces the iron (III) oxide in haematite to iron. The iron formed is molten and runs to the bottom of the furnace. Fe2O3(s) + 3CO (g) --> 2Fe(l) + 3CO2(g) 4. Limestone (calcium carbonate) is decomposed by heat to produce carbon dioxide and calcium oxide (quicklime). CaCO3(s) --> CO2(g) + CaO(s) Calcium oxide (basic) reacts with silicon dioxide (acidic), and with other impurities in haematite to form molten slag (calcium silicate). CaO(s) + SiO2(s) --> CaSiO3(l) Hot waste gases containing carbon monoxide, carbon dioxide and nitrogen escape through the top of the furnace. The molten slag runs to the bottom of the furnace. It floats on top of the molten iron. The slag and iron are tapped off separately.

Differences between Addition Polymerisation and Condensation Polymerisation

1. The monomers in addition polymerisation have C=C double bonds while the monomers in condensation polymers have two different functional groups - acids and alcohols or amines. 2. In addition polymerisation, monomers join together without the loss of a small molecule. In condensation polymerisation, a small atom or molecule like water is lost when monomers form the polymer. 3. Monomers in an addition polymer are joined together by C-C single bonds, while monomers in a condensation polymer are joined together by amide or ester linkages.

Depletion of Ozone Layer

1. The ozone layer filters out some of the harmful ultraviolet radiation from the sun. 2. Too much ultraviolet radiation reaching the Earth could lead to skin cancer, genetic mutations and eye damage. 3. CFCs reacts with ozone in the stratosphere and cause the depletion of the ozone layer.

How do the physical properties of alkanes change on going down the series?

1. Their melting and boiling points increase 2. They become more viscous (i.e. thicker) 3. They become less flammable

What are things to note when setting up distillation apparatus?

1. Thermometer. Bulb of thermometer should be placed beside the side arm of the distillation flask. It should not be dipped into the solution. This ensures that the thermometer measures the boiling point of the substance that is being distilled. 2. Condenser. Condenser should slope downwards and cold running water is allowed to enter the water jacket from the bottom of the condenser and leave from the top. This ensures that the pure solvent formed runs downwards into the receiver. Water entering from the bottom ensures that the entire jacket is always completely filled, providing a more efficient cooling system. 3. Receiver If the distillate is volatile, the receiver can be put into a large container filled with ice. This helps to keep the temperature of the distillate low so that it remains in the liquid state.

How can we measure the pH of a given solution?

1. Universal Indicator: pH 0-15. Red, Orange, Yellow, Green, Blue, Purple 2. Methyl Indicator Acid: Red Change colour: pH 3-5 Alkali: yellow 3. Screened Methyl Orange Acid: Violet Change colour: 3-5 Alkali: Green 4. Bromothymol Blue Acid: Yellow Change colour: 6-8 Alkali: Blue 5. Phenolphthalein Acid: Colourless Change colour: 8-10 Alkali: Pink

Rust Prevention

1. Using a Protective Layer - Coat with a layer of oil/grease, paint or plastic or electroplating with less reactive metal - Prevents metal from coming into contact with oxygen and water - If the protective layer is scraped off, the metal is exposed to water and oxygen and corrosion will occur (for iron it's rusting) - Uses: Motor cars, ships, cans of food, bicycles 2. Sacrificial Protection - Coat with a layer of Zn (galvanising) - Attaching blocks of Zn or Mg metals to iron or steel - Zn is more reactive than Fe. Hence it reacts more readily with oxygen and water and corrodes preferentially in place of iron. The Zn layer will continue to protect the iron even if their layer is scratched 3. Use of alloys - Using alloys like stainless steel - Stainless steel contains nickel, chromium, carbon and iron. When exposed to air and moisture, a very hard coating of chromium (III) oxide forms on the surface of stainless steel, protecting it from further corrosion. - However it is expensive - Cutlery, surgical instruments

How do we separate solids?

1. Using a Suitable Solvent. To separate a mixture of two solids, we use a solvent in which only one solid is soluble. (The other solid is insoluble) 2. Sublimation Sublimation is used to separate a solid that sublimes from one that does not. Some substances, such as iodine, sublime on heating. Other substances, such as sand, does not sublime. 3. Using a Magnet A magnet can be used to separate a magnetic substance from a non-magnetic substance

What does air consist of?

78% Nitrogen 21% Oxygen 1% Other gases: • Noble gases (mostly argon) 0.97% • Carbon dioxide 0.03% Separated by fractional distillation of liquified gases. Nitrogen distils over first, followed by argon and then oxygen.

What is a base?

A base is any metal oxide or hydroxide that reacts with an acid to produce salt and water only.

Characteristics of a Catalyst

A catalyst is a substance which increases the speed of a chemical reaction and remains chemically unchanged at the end of the reaction. They increase the speed of reaction by providing an alternative pathway for the reaction to proceed. The catalysed reaction has a lower activation energy than without the catalyst.

What is a compound?

A compound is a pure substance containing two or more elements that are chemically combined in a fixed ratio

What is a covalent bond?

A covalent bond is a bond formed by the sharing of electrons between two atoms

What is a functional group?

A functional group is an atom or a group of atoms that gives a molecule its characteristic properties.

What is a homologous series?

A homologous series is a family of organic compounds with the same functional group and similar chemical properties. General characteristics: - Same functional group - Similar chemical properties - Gradual change in physical properties as we go down the series - Same general formula

What are macromolecules?

A macromolecule is a very large molecule that is made up of many small molecules.

What is a metallic bond?

A metallic bond is the electrostatic forces of attraction between positive metal ions and the sea of delocalised electrons

What is a mixture?

A mixture is made up of two or more substances that are not chemically combined

What are molecules?

A molecule is a group of two or more atoms that are chemically combined.

Displacement Reaction of Metals

A more reactive metal can displace a less reactive metal from its salt solution.

What are polymers?

A polymer is a type of long-chain molecule that is linked together by many small repeat units known as monomers. The process of joining together a large number of monomers to form a polymer is called polymerisation.

What are atoms made of?

A proton (part of nucleus) - has a relative charge of +1 - has a relative mass of 1 - is represented by the symbol p A neutron (part of nucleus) - has a relative charge of 0 - has a relative mass of 1 - is represented by the symbol n An electron (move rapidly around the nucleus) - has a relative charge of -1 - has a relative mass of 1/1840 - is represented by the symbol e

What is a pure substance?

A pure substance is made up of one single element or compound. It is not mixed with any other substance

Separating liquids with a Separating Funnel

A separating funnel can be used to separate immiscible liquids. 1. Pour the mixture of oil and water into the separating funnel. 2. Support the separating funnel using a retort stand, Then place a clean beaker below the separating funnel 3. Allow the liquids to separate completely. This may take some time. The denser liquid will be the bottom layer. 4. Open the tap of the funnel to allow the bottom layer to drain into the beaker. Close the tap before the top layer of liquid runs out. 5. Place another beaker below the funnel. Open the tap to allow a little of the top layer of liquid into the beaker. Dispose of the liquid collected. Now, the separating funnel contains only il while the beaker from step 4 contains only water.

Pure solids and liquids

A solid is pure if it has an exact and constant (or fixed) melting point A liquid is pure if it has an exact and constant (or fixed) boiling point

What is a strong acid?

A strong acid is an acid that is completely ionised in aqueous solution

What is a weak acid?

A weak acid is an acid that is only partially ionised in aqueous solution

Why does a gas not have a fixed shape or a fixed volume?

According to the kinetic particle theory, the particles of a gas are spread far apart from one another and have weaker forces of attraction than the particles of a liquid. In addition, they have a lot of kinetic energy and are not held in fixed positions and hence can move about rapidly in any direction. Thus, a gas has no fixed shape. The particles of a gas have a lot more space between them as compared to the particles of a liquid or solid. The large space between the particles allows the gas to be easily compressed when pressure is applied. I.e. the particles of a gas can be forced to move closer together. Since a gas can be compressed, it has no fixed volume.

Why does a liquid not have a fixed shape but have a fixed volume?

According to the kinetic particle theory, the particles of a liquid are arranged in a disorderly manner and have weaker forces of attraction than the particles of a solid. However they have more kinetic energy than particles of the same substance in the solid state, and are not held in fixed positions but instead can move freely throughout the liquid. Thus liquid has no fixed shape The particles of a liquid are further away from one another than the particles of a solid. However, the liquid particles are still packed quite closely together. Thus a liquid cannot be compressed and has a fixed volume.

Why do solids have a fixed shape and volume?

According to the kinetic particle theory, the particles of a solid are closely packed in an orderly manner and are held together by very strong forces of attraction. In addition, the particles have enough kinetic energy to only vibrate and rotate about their fixed positions and cannot move about freely. Thus solid has a fixed shape A solid cannot be compressed since its particles are already very close to one another. Thus, a solid has a fixed volume.

Types of Oxides

Acidic Oxides: - Most oxides of non-metals Basic Oxides: - Most oxides of metals Amphoteric Oxides: - Metallic oxides that can react with both acids and bases to form salts and water. - Zinc oxide, aluminium oxide and lead(II) oxide are all amphoteric Neutral Oxides: - Some non-metals form oxides that show neither basic nor acidic properties. These oxides are called neutral oxides and are insoluble in water. - E.g. water, carbon monoxide, nitric oxide

What is activation energy?

Activation energy, [E subscript a], is the minimum amount of energy that reactant particles must possess in order for a chemical reaction to occur

Addition Polymerisation

Addition polymerisation occurs when unsaturated monomers join together without losing any molecules or atoms. The polymer formed is called an addition polymer. The monomer must be unsaturated!

Advantages and Limitations of Recycling Metals

Advantages: - Conserves Earth's natural resources - Saves energy - Reduces pollution - Produces jobs for people Limitations: - Public apathy - Small percentage that can be recycled are recycled. People need to be educated and encouraged to recycle - Requires purpose-built factories - Collection of metals for recycling from households and industries poses a problem

Advantages and Disadvantages of using Hydrogen as a Fuel

Advantages: 1. Hydrogen does not cause pollution. Only water is produced in the combustion of hydrogen. [O2(g) + 2H2(g) --> 2H2O(l)] 2. Hydrogen is a renewable source of energy. Hydrogen can be obtained from the electrolysis of water 3. Hydrogen is an efficient source of energy. When it burns, it releases more than twice the amount of energy compared to many other fuels. Disadvantages: 1. There are no cheap sources of hydrogen. Obtaining hydrogen from electrolysis is expensive hence it is currently obtained from non-renewable sources like petroleum. 2. Hydrogen is extremely flammable and explosive. Special precautions must be take in the storage and transport of the gas 3. Hydrogen is very light. Hydrogen requires larger storage volumes compared to other fuels.

Producing Ethanol by Fermentation

Alcoholic drinks such as beer and wine contain ethanol. To produce ethanol, we ferment fruits, vegetables or grains. Alcohol fermentation is a process in which micro-organisms such as yeast act on carbohydrates like glucose in the absence of oxygen to produce ethanol and carbon dioxide. *Temperature should be kept around 37°C

What are alcohols?

Alcohols are a homologous series of organic compounds which have the hydroxyl (-OH) functional group. General Formula: CnH2n+1OH Physical properties of alcohols: - Solubility decreases as the molecular size increases - Boiling point increases as the molecular size increases. This is because as the sizes of alcohol molecules increase, the forces of attraction between molecules also increase.

What are alkanes?

Alkanes are a homologous series of hydrocarbons that contain only carbon-carbon single covalent bonds. General Formula: CnH2n+2 Physical Properties: - low melting and boiling points - are insoluble in water - are soluble in organic solvents Chemical Properties: - generally unreactive

What are alkenes? (aka unsaturated hydrocarbons)

Alkenes are a homologous series of hydrocarbons that contain one or more carbon-carbon double bonds. General Formula: CnH2n Physical properties: - low melting and boiling points which increases down the series

Polyatomic Ions

Ammonium - NH subscript 4 superscript + Phosphate - PO subscript 4 superscript 3- Carbonate - CO subscript 3 superscript 2- Sulfate - SO subscript 4 superscript 2- Nitrate - NO subscript 3 superscript - Hydroxide - OH superscript -

What is an acid?

An acid is a substance that produces hydrogen ions, H superscript +, in aqueous solutions. E.g. HCl (aq) --> H+(aq) + Cl-(aq)

What is an addition reaction?

An addition reaction is a reaction in which an unsaturated organic compound combines with another substance to form a single new compound

What is an alkali?

An alkali is a substance that produces hydroxide ions, OH-, in aqueous solution.

What is an alloy?

An alloy is a mixture of a metal with one or a few other elements

What is an element?

An element is a pure substance that cannot be broken down into two or more simpler substances by chemical processes

What are esters?

An ester is a colourless liquid that is insoluble in water. They have the functional group -COO- Esters are formed by the reaction of a carboxylic acid and an alcohol (esterification) in the presence of conc. sulfuric acid and heat. [Reversible reaction!]

Simple Cell

Anode: Negative electrode Cathode: Positive electrode More reactive metal becomes anode (negative electrode) while less reactive metal becomes cathode. (positive electrode)

Electrolytic Cell

Anode: Positive electrode Cathode: Negative electrode

Testing for an Oxidising Agent

Aqueous solution: - Add aqueous KI to unknown solution - Brown solution is formed - Iodide ions are oxidised to iodine by oxidising agent Gas: - Dip a piece of starch-iodide paper in the unknown solution - Starch-iodide paper turns from white to blue - Iodide ions are oxidised to iodine by the oxidising agent. The iodine produced reacts with the starch to give a blue colour

Testing for a Reducing Agent

Aqueous solutions: - Add acidified aqueous potassium manganate (VII) to the unknown solution - Colour of potassium manganate (VII) solution changes from purple to colourless - Manganate (VII) ion is reduced to manganese (II) ion. Oxidation state of manganese decreases from +7 to +2 Gas: - Place a piece of filter paper soaked with potassium manganate (VII) at the mouth of the test tube - Acidified potassium manganate (VII) paper turns from purple to colourless - Manganate (VII) ion is reduced to manganese (II) ion. Oxidation state of manganese decreases from +7 to +2

What are atoms?

Atoms are the smallest particles of an element that have the chemical properties of that element

What is boiling?

Boiling is the process by which a substance changes from a liquid to a gas at the boiling temperature of the substance without a change in temperature

In what way is evaporation different from boiling?

Boiling: - Occurs only at boiling point - Occurs throughout the liquid - Occurs rapidly Evaporation: - Occurs at temperatures below boiling point and above melting point - Occurs only at the surface the liquid - Occurs slowly

Difference between Fats and Oils

Both are polyunsaturated compounds because their hydrocarbons contain more than one carbon-carbon double bond. Fats are solids at r.t.p. and contain mainly saturated fat molecules. Oils are liquids at r.t.p. and contain a higher percentage of unsaturated fat molecules.

Examples of Alloys, their Compositions, Properties and Uses

Brass: Copper + Zinc - Does not corrode easily, attractive yellow colour similar to gold - Used for decorative ornaments, musical instruments and coins Bronze: Copper + Tin - Does not corrode easily - Used for making coins, idols and utensils Stainless steel: Iron + Carbon + Chromium + Nickel - Resistant to corrosion - Used in cutlery, utensils, medical instruments, pipes in chemical industries Steel: Iron + Carbon - Resistant to corrosion - Used for making nails, screws and bridges

Identifying Anions

Carbonate ion: Test: 1. Add dilute hydrochloric acid. 2. Pass the gas given off through limewater. Observations: 1. Effervescence is observed 2. Gas given off forms a white ppt in limewater. Carbon dioxide gas is given off Nitrate ion: Test: 1. Add sodium hydroxide solution, then add a piece of aluminium foil. Warm the mixture 2. Test the gas given off with a piece of moist red litmus paper Observations: 1. Effervescence is observed 2. Moist red litmus paper turns blue. Ammonia gas is given off Sulfate ion: Test: Add dilute nitric acid, then add barium nitrate solution. Observations: A white ppt of barium sulfate is formed Chloride ion: Test: Add dilute nitric acid, then add silver nitrate solution Observation: A white ppt of silver chloride is formed Iodide ion: Test: Add dilute nitric acid, then add silver nitrate solution Observation: A yellow ppt of silver iodide is formed

What are carboxylic acids?

Carboxylic acids are a homologous series of organic acids which have the carboxyl (-COOH) functional group General Formula: CnH2n+1COOH Carboxylic acids are produced through oxidation of alcohols using acidified potassium manganate(VII) Physical properties: - Boiling points increase as the molecular size increases. Low m.p. and b.p.

Decomposition of Compounds

Chemical processes such as thermal decomposition and electrolysis can be used to decompose compounds. Thermal decomposition involves heating a compound strongly. Electrolysis is the process of using electricity to break down a compound

What is chromatography?

Chromatography is the method of separating two or more components that dissolve in the same solvent. Procedure: 1. Draw a line with a pencil at about 1cm from the bottom of a strip of filter paper or chromatography paper. 2. Put a drop of the green food colouring on the pencil line. Allow the drop to dry 3. Dip the paper into a glass tank containing the solvent, in this case, ethanol,. Ethanol that is soaked up by the paper will dissolve the dyes 4. Leave the apparatus to stand for a while. Ethanol will travel up the paper, carrying the dyes along. The more soluble a dye is in ethanol, the further it will move up the paper.

Fuels as a source of energy

Complete combustion: organic compound + oxygen --> carbon dioxide + water vapour Incomplete combustion: organic compound + oxygen --> carbon monoxide + carbon + water vapour

What is condensation?

Condensation is the process by which a gas changes to a liquid.

Condensation Polymerisation

Condensation polymerisation occurs when monomers combine to form a polymer, with the removal of a small molecule such as water.

What is crystallisation?

Crystallisation is used for obtaining a pure solid sample from its solution. (Also for substances that decompose when heated strongly) In crystallisation, water is removed by heating the solution. Heating is stopped at the stage when a hot saturated solution is formed. When the resulting solution is left to cool to room temperature, the dissolved solid will form as pure crystals.

Displacement of Water to Collect a Gas

Displacement of Water - is suitable for collecting gases that are insoluble or slightly soluble in water. Carbon dioxide, hydrogen or oxygen can be collected by this method.

Downward Delivery to Collect a Gas

Downward delivery - is used to collect gases that are soluble in water and denser than air (N2), such as chlorine and hydrogen chloride.

What is Electrolysis

Electrolysis is the process of using electricity to break down or decompose a compound.

Producing Ethanol from Ethene

Ethanol is produced by the catalytic addition of steam to ethene at 300°C and 60atm with a H3PO4 catalyst.

What is evaporation?

Evaporation is the process by which a liquid changes to a gas at temperatures lower than its boiling point but higher then its melting point. Evaporation occurs because some particles have enough energy to escape as a gas from the surface of the liquid. - Liquids that evaporate quickly at room temperature are called volatile liquids.

What is evaporation to dryness?

Evaporation to dryness is used to obtain a soluble solid from a solution by heating the solution until all the water has boiled off. However the solid obtained is not always pure as soluble impurities will be left together with the solid. In addition, some substances may decompose.

Methods for Collecting Gases

Factors to take note: 1. Solubility - how soluble the gas is in water 2. Density - how dense the gas is compared to air

What is filtration?

Filtration is used to separate insoluble solid particles from a liquid. Procedure: 1. Pour the mixture into a filter funnel that is lined with filter paper 2. Collect the filtrate (the solution that drips through) in a conical flask. 3. Collect the residue and dry it on a piece of filter paper How??? A liquid can pass through the pores of the filter paper but a solid cannot do so. The solid that remains is the residue while the solution that passes through is the filtrate

What is Fractional Distillation

Fractional distillation is used to separate a mixture of miscible liquids with different boiling points. The liquid with the lowest boiling point will distil over first. E.g. Solution of ethanol and water 1. Ethanol vapour and water vapour rise up to the column as the solution is heated 2. The water vapour condenses in the fractioning column and falls back into the flask 3. Ethanol, which has a lower boiling point than water, reaches the upper part of the column and is distilled over. 4. At this stage, the thermometer shows a constant temperature of 78°C, which is the boiling point of ethanol. 5. In the condenser, hot ethanol vapour condenses as running water cools it, forming liquid ethanol which flows down the inner tube of the condenser and into the receiving flask (conical flask) 6. Ethanol is collected as the distillate in the receiver. 7. When all the ethanol has distilled over, the temperature rises rapidly to 100°C, which is the boiling point of water. At this temperature, water distils over and can be collected separately.

What is freezing?

Freezing is the process by which a substance changes from liquid state to solid state without a change in temperature.

Global Warming and its Consequences

Global warming is the increase in the Earth's average temperature due to the build-up of greenhouse gases in the atmosphere. Consequences: - More occurrences of unusual weather conditions such as warm spells, droughts, unexpected storms and hurricanes, floods and tsunamis in some parts of the world - Decrease in crop yields world-wide because areas that are currently covered by vegetation become deserts - Melting of large quantities of ice in the North Pole and South Pole. This will cause ocean levels to rise and flood low-lying countries such as the Netherlands

What happens to the particles of a gas when the gas condenses?

Heat energy is given out by the gas particles during condensation. As the temperature drops, the gas particles lose energy and move more slowly. Eventually, the movement of the particles becomes slow enough for the gas to change to a liquid.

The Carbon Cycle

How is Carbon Dioxide added? 1. Respiration 2. Combustion of fuels (excess CO2 added) 3. Decay and bacterial decomposition How is Carbon Dioxide removed? 1. Photosynthesis 2. Ocean uptake

Identifying Gases

Hydrogen gas: - Colourless and odourless - Place a lighted splint at the mouth of the test tube - The lighted splint is extinguished with a loud 'pop' sound Oxygen gas: - Colourless and odourless - Insert a glowing splint into the test tube - The glowing splint is rekindled Carbon dioxide: - Colourless and odourless - Bubble gas through limewater [Ca(OH)2] - A white ppt is formed. The ppt dissolves upon further bubbling Chlorine gas: - Greenish-yellow gas with a pungent smell - Place a piece of moist blue litmus paper at the mouth of the test tube - The moist blue litmus turns red, and is then bleached Sulfure dioxide gas: - Colourless gas with a pungent smell - Place a piece of filter paper soaked with acidified potassium manganate (VII) at the mouth of the test tube - The purple acidified potassium manganate (VII) turns colourless Ammonia gas: - Colourless gas with a pungent smell - Place a piece of moist red litmus paper at the mouth of the test tube - The moist red litmus paper turns blue

Solubility and Density of Gases

Hydrogen: Not soluble, Less dense than air Oxygen: Very slightly soluble, Less dense than air Carbon dioxide: Slightly soluble, Denser than air Chlorine: Soluble, Denser than air Hydrogen chloride: Very soluble, Denser than air Sulfur dioxide: Very soluble, Denser than air Ammonia: Extremely soluble, Less dense than air

Why are alloys stronger and harder than their constituent metals?

In an alloy, the atoms of the different metals or elements have different sizes. The regular arrangement of atoms in the pure metal is disrupted. The atoms of different sizes cannot slide over each other easily when a force is applied. As a result, an alloy is stronger and harder than the pure metal.

What are ionic bonds?

Ionic bonds are the strong electrostatic forces of attraction between positive and negative ions

Giant Lattice Structure

Ionic compounds form giant lattice structures. A giant lattice structure is a three-dimensional network of ions. - The ions are held in place by ionic bonds. - The ions are packed in a regular and repeating pattern. - The giant lattice structure is held together tightly because the oppositely charged ions attract one another strongly.

What are isomers?

Isomers are compounds that have the same molecular formula but different structural formula.

What are isotopes?

Isotopes are atoms of the same element with the same number of protons and electrons, but different number of neutrons. Isotopes have the same chemical properties but slightly different physical properties.

What is a reversible reaction?

It is a reaction that can go both forward and backward at the same time

Nylon - A Synthetic Polyamide

It is made from a dicarboxylic acid and a diamine. Dicarboxylic acid: a molecule with two -COOH groups Diamine: a molecule with two -NH2 groups Nylon is a polyamide as it contains many amide linkages. The amide linkage is usually written as -CONH- Uses: 1. Strong ropes and fishing lines 2. Woven into cloth to make nylon tents, parachutes and raincoats Strong, light and stretchable without breaking

What is diffusion?

It is the movement of particles from a region of higher concentration to a region of lower concentration !! Gases with lower molecular masses diffuse faster than those with higher molecular masses!! !! The higher the temperature, the higher the rate of diffusion!!

What is sublimation?

It is the process by which a solid changes directly to a gas without going through the liquid state.

Water of Crystallisation

Many salts combine with water molecules to form crystals. These water molecules are known as water of crystallisation. The water of crystallisation can be removed by heating hydrated salts to produce anhydrous salts. Hydrated salt can be obtained from anhydrous salt by adding water

How is margarine produced?

Margarine is produced through hydrogenation of vegetable oil at 200°C with a nickel catalyst.

Measurements and their instruments

Mass (g, not SI) - Electronic balance. Time (nearest s) - Stopwatch Temperature (°C) - Thermometer Volume (cm^3) - Liquids: Burette (accurate variable volume), Pipette (accurate fixed volume), Measuring Cylinder (approximate) - Gas: Gas syringe

What is melting?

Melting is the process in which a substance changes from solid to liquid state without a change in temperature

Differences between compounds and mixtures

Mixture: - Components can be separated by physical processes such as magnetic separation, filtration or distillation. - The chemical properties of a mixture are the same as those of its components - No chemical reaction takes place when a mixture is formed -- usually there is little or no energy change - The components of a mixture can be mixed in any proportion Compound: - A compound can only be broken down into its elements or into simpler compounds by chemical processes and not by physical means - The physical and chemical properties of a compound are different from those of its constituent elements - A chemical reaction takes place when a compound is formed -- usually there is an energy change, e.g. the reactants get hot or cold -The elements in a compounds are always combined in a fixed proportion

Poly(ethene)

Monomer: H3C=CH3 Repeat Unit: -(-CH2-CH2-)- Structure of Poly(ethene): -(-CH2-CH2-)- subscript n Uses: Making items such as plastic bags, toys, buckets and clingfilm

Simple Molecular Structures

Most covalent substances, such as bromine, exist as simple molecules. These substances have simple molecular structures

Reaction of nitrogen and hydrogen to form ammonia

N2(g) + 3H2(g) ⇌ 2NH3(g) Conditions: - 200atm - 450°C - Iron Catalyst

Formation of Negative Ions (Anions)

Negative ions or anions are formed when atoms gain electrons

In what way do noble gases behave differently from other elements?

Noble gases are monoatomic and exist as individual atoms. These atoms are stable and unreactive. They do not usually react with other elements to form compounds. Atoms of most other elements are reactive. They combine with other atoms to form molecules or compounds.

Common Oxidising and Reducing Agents

Oxidising Agents: 1. Acidified Potassium Manganate (VII) [KMnO4] Purple to colourless 2. Acidified Potassium Dichromate (VI) [K2Cr2O7] Orange to green Reducing Agents: 1. Potassium iodide [KI] Colourless to brown

Group VII Elements - Halogens

Physical Properties: - have low melting and boiling points - are coloured - m.p. and b.p. of halogens increase down the group - colour of halogens become darker down the group Chlorine gas (greenish-yellow) -> Bromine (reddish-brown liquid) -> Iodine solid (purplish-black solid) Chemical Properties: - more reactive halide will displace a less reactive halogen from its halide solution - powerful oxidising agents (Iodine solution is brown, all halogens are diatomic no matter the state)

Group I Metals - Alkali Metals

Physical properties: - soft and can be cut easily - have low melting and boiling points - have low densities Chemical properties: - are highly reactive - reactivity increases down the group - powerful reducing agents

Plastics are non-biodegradeable

Plastics cannot be broken down by bacteria in the soil. 1. They build up in landfill and lead to an increasing amount of build-up waste. 2. Upon incineration they produce poisonous gases. 3. Plastics thrown into the sea endanger marine animals and may clog up rivers and drains which become breeding grounds for mosquitoes.

Formation of Positive Ions (Cations)

Positive ions or cations are formed when atoms lose electrons

Reaction of Metals with Dilute Hydrochloric Acid

Potassium: - Reacts explosively. Do not try in school lab. [pls do so i don't have to take Os] Sodium: - Reacts explosively. Do not try in school lab Calcium: - Reacts violently to give hydrogen gas Magnesium: - Reacts rapidly to give hydrogen gas Zinc: - Reacts moderately fast to give hydrogen gas Iron: - Reacts slowly to give hydrogen gas Lead: - No reaction occurs (Observation). Actually got reaction but insoluble layer of lead(II) chloride is produced so no observable reaction Copper, silver: - No reaction occurs

Reactions of metals with Cold Water and Steam

Potassium: - Reacts very violently with cold water to form potassium hydroxide and hydrogen gas. Enough heat is produced to cause hydrogen gas to catch fire and explode - Reacts explosively with steam. This reaction should not be carried out in the school lab lmao Sodium: - Reacts violently with cold water to form sodium hydroxide and hydrogen gas. Hydrogen gas may catch fire and explode - Reacts explosively with steam Calcium: - Reacts readily to from calcium hydroxide and hydrogen gas - Reacts explosively with steam Magnesium: - Reacts very slowly with cold water to form magnesium hydroxide and hydrogen gas. A test tube of hydrogen gas is produced only after a few days - Hot magnesium reacts violently with seam to form magnesium oxide (a white solid) and hydrogen gas. A bright white glow is produced during this reaction Aluminium: - No reaction occurs - No reaction occurs - Aluminium reacts with oxygen in the atmosphere to form insoluble Al2O3 Zinc: - No reaction occurs - Hot zinc reacts readily with steam to produce zinc oxide and hydrogen gas. Zinc oxide is yellow when hot and white when cold. Iron: - No reactions occurs - Red-hot iron reacts slowly with steam to form iron oxide and hydrogen gas. The iron must be heated constantly in order for the reaction to proceed - Iron reacts very slowly with water in the presence of air, in a process called rusting Lead, Copper, Silver: - No reaction occurs - No reaction occurs

Naming of Covalent Compounds

Prefixes are used to indicate the number of atoms of the element. (If there is only one atom of the first element, mono is not needed. E.g. Nitrogen dioxide) Mono - one Di - two Tri - three Tetra - four

Use of Petroleum Fractions

Pretty Girls - Petroleum gas: Fuel for cooking and heating Push - Petrol: Fuel for motorcars Naughty - Naphtha: Raw material for making petrochemicals such as plastics and detergent Kids - Kerosene (Paraffin): Fuel for aircraft engines, cooking using oil stoves and heating Down - Diesel: Fuel for diesel engines in buses, lorries and trains London - Lubricating Oil: For lubricating machines, for waxes and polishes Bridge - Bitumen: For making road surfaces and roofing

Transition Elements

Properties: - high melting and boiling points - high densities - have variable oxidation states in their compounds - form coloured compounds - transition metals and their compounds are good catalysts Iron is a catalyst for Haber process, nickel is used for manufacture of margarine from vegetable oil

Group 0 Elements - Noble Gases

Properties: - monoatomic - colourless gases at room temperature - low melting and boiling points - insoluble in water - unreactive Uses: - Helium is used for filling weather or advertisement balloons and airships - Argon is used to fill tungsten bulbs. It provides an inert atmosphere that prevents oxidation of filament - Neon is used in making lights and advertising signs - Xenon is used in vehicle headlamps

Endothermic Reactions

Reactions where heat is absorbed: 1. Photosynthesis [6CO2 + 6H2O --> C6H12O6 + 6O2] 2. Action of light on silver bromide in photographic film 3. Thermal decomposition ΔH>0

Exothermic Reactions

Reactions where heat is given out: 1. Combustion of fuels 2. Respiration [C6H12O6 + 6O2 --> 6CO2 + 6H2O] 3. Neutralisation 4. Corrosion of metals ΔH<0

Similarities and Differences of Alkanes and Alkenes

Similarities: 1. Both alkanes and alkenes are hydrocarbons 2. Both alkanes and alkenes are flammable. On complete combustion, they form carbon dioxide and water. Differences: 1. Alkanes contains only single bonds between carbon atoms while alkenes contain double bonds between carbon atoms 2. Alkanes are generally unreactive while alkenes very reactive 3. Alkanes undergo substitution reactions while alkenes undergo addition reactions 4. Alkanes do not react with aqueous bromine while alkenes rapidly decolourise aqueous bromine. 5. Alkanes produce a less smoky flame than an alkene with a similar number of carbon atoms. (i.e. less carbon is produced) 6. Alkanes do not undergo polymerisation while alkenes undergo addition polymerisation

What is Simple Distillation

Simple distillation is used to separate a pure solvent (liquid) from a solution. E.g. pure water from salt solution: 1. In the distillation flask, the solution boils. Boiling chips are added to ensure smooth boiling. Water vaporises, rises and enters the condenser. 2. In the condenser, water vapour is cooled. The vapour condenses and changes back into pure water (the distillate) which is collected in the receiver (a conical flask). 3. The salt solution, which remains the distilled flask, becomes more concentrated as distillation continues. If distillation is allowed to carry on, a solid residue of salt will be left in the flask.

How can we make soil less acidic?

Soil that is too acidic can be treated with quicklime (calcium oxide) or slaked lime (calcium hydroxide). This is known as 'liming' the soil. The bases reacts with the acids in the soil and raise the pH so that the plants grow healthily.

Some Observations for Displacement Reactions

Solids: • Zinc - grey • Copper - reddish-brown • Lead - grey • Iron - grey

Structure of Diamond and its Properties

Structure: Diamond is a substance with a tetrahedral structure. Each carbon atom is covalently bonded to four other carbon atoms. This forms a tetrahedral structure. (Also same idea for silicon dioxide) 1. High melting and boiling point Each carbon atom is covalently bonded to four other carbon atoms. This forms a tetrahedral structure. A lot of energy is required to break the covalent bonds between atoms. 2. Diamond does not conduct electricity All the valence electrons of the carbon atoms are used for bonding and there are no mobile ions. Hence there are no mobile charged particles to act as charge carriers to conduct electricity. 3. Hard AF ;) Each carbon atom is covalently bonded to four other carbon atoms. This forms a tetrahedral structure. A lot of energy is required to break the covalent bonds between atoms.

Structure of Graphite and its Properties

Structure: Graphite is made up of an extensive network of hexagonal shapes. Each carbon atom uses 3 valence electrons to form 3 covalent bonds with 3 other carbon atoms to form hexagonal layers of carbon atoms with weak van der Waals' forces of attraction between layers. The fourth valence electron is delocalised between layers of carbon atoms. 1. High melting and boiling point The entire structure is composed of an extensive network of atoms joined together by strong covalent bonds that require a lot of energy to break. 2. Graphite is soft and slippery Weak van der Waal's forces of attraction exist between layers of carbon atoms and require little energy to overcome. Hence the layers can slide over each other easily when a force is applied. 3. Conducts electricity Each carbon atom has one outer electron that is not used to form covalent bonds and are delocalised. These electrons can move freely along the carbon layers. The delocalised electrons can act as mobile charge carriers and conduct electricity.

Structure of Metals and their Properties

Structure: Metals have giant lattice structures. In a metal lattice, metal atoms lose their valence electrons and become positively charged ions. These valence electrons no longer belong to any metal atom and are mobile, moving freely between metal ions. Hence a metal lattice structure is said to be made up of a lattice of positive ions surrounded by a 'sea' of delocalised electrons. 1. Good conductors of electricity and heat The sea of delocalised electrons are able to move around freely and can act as mobile charge carriers to conduct electricity. 2. Have high melting and boiling point Positive metal ions and sea of delocalised electrons have strong electrostatic forces of attraction between them. Hence a large amount of energy is need to overcome these strong forces of attraction. 3. Have high densities Atoms in a metal are packed tightly in laters and are held together by strong metallic bonds. 4. Malleable and ductile i.e. Metals can be hammered into different shapes (malleable) and drawn into wires without breaking (ductile). When a force is applied, the layers of metal atoms can slide over each other through the 'sea of electrons'. The metallic bonding is not disrupted.

Why do solids sublime and how are they useful?

Sublimation occurs because particles at the surface of the solid have enough energy to break away from the solid and escape as a gas. e.g. Ammonium chloride and iodine Dry ice (solid carbon dioxide) is used for industrial refrigeration and transporting frozen food.

Giant Molecular Structures

Substances that exist as a giant network of atoms that are covalently bonded together are said to have giant molecular structures. Examples are diamond, graphite and silicon dioxide. Diamond and graphite are allotrope of carbon, i.e. different forms of carbon

How does Flue Gas Desulfurisation work?

Sulfur dioxide reacts with calcium carbonate to form solid calcium sulfite and carbon dioxide gas. CaCO3(s) + SO2(g) --> CaSO3(s) + CO2(g) Calcium sulfite is further oxidised to form calcium sulfate by atmospheric oxygen. 2CaSO3(g) + O2(g) --> 2CaSO4(s)

When does reduction take place?

Takes place if a substance: - gains electrons - decreases in oxidation state - loses oxygen - gains hydrogen

When does oxidation take place?

Takes place if a substance: - loses electrons - increases in oxidation state - gains oxygen - loses hydrogen

Terylene - A Synthetic Polyester

Terylene is another example of a condensation polymer. Terylene is made from a dicarboxylic acid and a diol. Dicarboxylic acid: A molecule with two -COOH groups Diol: A molecule with two -OH groups Terylene is a polyester as it contains many ester linkages. The ester linkage is usually written as -COO- Uses: 1. Clothing, curtain material, parachutes, sails and sleeping bags Strong, light and elastic

Esterification

The carboxylic acid will lose -OH while the alcohol will lose -H. The ester is named with the alcohol first followed by the acid. -yl -anoate

How do we interpret the result of paper chromatography?

The chromatography paper with the separated components is called a chromatogram. The ratio between he distance travelled by the substance and the distance travelled by the solvent is a constant. This ratio is called the retention factor or Rf value of a substance. Rf = (distance travelled by substance)/(distance travelled by solvent) Rf < 1!!!! A locating agent is used to make colourless substances show up as coloured spots.

What is the kinetic particle theory?

The kinetic particle theory states that all matter is made up of tiny particles and that these particles are in constant random motion

Action on Heat on Metal Carbonates

The more reactive a metal is, the more difficult it is to decompose its carbonate by heat. Metal carbonate --> metal oxide + carbon dioxide Potassium & sodium carbonate - Unaffected Calcium - copper (II) carbonate - decompose into metal oxide and carbon dioxide on heating Silver carbonate - decompose into silver and carbon dioxide on heating

Catalytic Cracking of Petroleum

The oil industry faces higher demands for short chain alkanes and alkenes that make part of crude oil fractions than the longer chain hydrocarbons. Through catalytic cracking, long-chain hydrocarbons can be cracked to produce more useful short-chain alkanes and alkenes and help to meet the demands the oil industry faces. Catalytic cracking occurs at high heat with an aluminium oxide catalyst.

Proton Number and Nucleon Number

The proton number of an atom refers to the number of protons in the atom (subscript) The nucleon number an atom is the total number of protons and neutrons in the atom (superscript)

What are valence electrons?

The valence shell of an atom refers to the shell that is furthest away from the nucleus of the atom. The electrons in the outer shell of an atom are known as valence electrons.

Upward Delivery to Collect a Gas

Upward delivery - used to collect gases that are soluble in water and less dense than air, such as ammonia

What do you observe when a liquid boils?

When a liquid boils, bubbles of gas are seen. These bubbles are formed when the liquid changes to a gas. The bubbles rise to the surface and escape into the air.

Testing for Cations using Sodium Hydroxide

Zinc ion - white ppt after a few drops, ppt dissolves in excess to form a colourless solution Aluminium ion - white ppt after a few drops, ppt dissolves in excess to form a colourless solution Lead (II) ion - white ppt after a few drops, ppt dissolves in excess to form a colourless solution Calcium ion - white ppt, ppt is insoluble in excess Copper (II) ion - light blue ppt, ppt is insoluble in excess Iron (II) ion - green ppt, ppt is insoluble in excess Iron (III) ion - reddish-brown ppt, ppt is insoluble in excess Ammonium ion - No ppt. On heating, ammonia gas is given off. Ammonia gas turns moist red litmus paper blue. No change on excess

Testing for Cations using aqueous ammonia

Zinc ion - white ppt, ppt dissolves in excess to form a colourless solution Aluminium ion - white ppt, ppt is insoluble in excess Lead(II) ion - white ppt, ppt is insoluble in excess Calcium ion - no ppt, no ppt in excess Copper (II) ion - light blue ppt, ppt dissolves in excess to form a deep blue solution Iron (II) ion - green ppt, ppt is insoluble in excess Iron (III) ion - reddish-brown ppt, ppt is insoluble in excess

Reduction of Metal Oxides with Carbon

metal oxide + carbon -heat-> metal + carbon dioxide The more reactive a metal is, the more difficult it is to reduce its oxide to the metal by carbon Potassium - Aluminium: Extracted via electrolysis Zinc - Gold: Extracted via reduction with carbon