AQA GCSE Chemistry - Paper 1

What is the charge of a proton?

+1

What is the charge of an electron?

-1

Describe giant covalent structures

-All the atoms are bonded to each other by strong covalent bonds -They have very high melting and boiling points, therefore, lots of energy is required to break the covalent bonds -Most of them don't conduct electricity because they don't contain delocalised electrons or ions

Give three examples of giant covalent substances

-Diamond -Graphite -Silicon Dioxide

Describe the properties of diamond

-Very hard because of its structure -Very high melting point because it takes a lot of energy to break the bonds -No delocalised electrons, therefore it cannot conduct electricity

Metals lower than carbon...

...Have to be extracted by carbon reduction

Metals higher than carbon...

...Have to be extracted by electrolysis

Cathode - If the element is more reactive than hydrogen...

...Hydrogen gas will be produced

Anode - If there are no halogen ions (halide ions)...

...Oxygen will be produced

For every decrease of 1 on the pH scale...

...The concentration of positive hydrogen ions increase by a factor of 10 - Logarithmic E.g. pH 4 has 10 times the concentration of pH 5

Cathode - If the element is less reactive than hydrogen...

...The element will be released from the cathode

The more solute there is in a given volume...

...The more concentrated the solution

Anode - If there are halogen ions (halide ions)...

...They will be released from the anode

What is the charge of a neutron?

0

Radius of an atom

0.1 nanometers

What is the relative mass of a neutron?

1

What is the relative mass of a proton?

1

What's the difference between a burette and a pipette?

1) A burette measures varying volumes 2) A pipette measures fixed volumes

Uses for nanoparticles

1) Catalysts 2) Nanomedicine - they could deliver drugs right into the cells when they're needed as they're more easily absorbed by the body 3) Tiny electric circuits for computer chips - some conduct electricity 4) Silver nanoparticles have antibacterial properties - added to polymer fibres that are used to make surgical masks & wound dressings and they're added to deodorants 5) Used in cosmetics e.g. to improve moisturisers without making them really oily

Empirical Formula

1) Divide the mass of each substance by its relative formula mass to find the number of moles 2) Divide the number of moles of each substance by the smallest number of moles in the reaction 3) If any of the numbers aren't whole numbers, multiply all the numbers by the same amount so that they all become whole numbers 4) Write the balanced symbol equation for the reaction by putting these numbers in front of the chemical formula

Why are hydrogen-oxygen fuel cells better than batteries for cars?

1) Don't produce as many pollutants as other fuels as the only by-products are water & heat - batteries for electric vehicles are polluting to dispose of due to the highly toxic metal compounds they contain 2) Batteries have a limit to the number of times they can be recharged and they're more expensive to make 3) Store less energy than fuel cells - would need to be recharged more often, and recharging takes a long time

Paper Chromatography - Method

1) Draw a pencil line near the bottom of a sheet of filter paper 2) Add a spot of ink to the line & place the sheet in a beaker of solvent e.g. water - the solvent used depends on what's being tested - some compounds dissolve well in water, but sometimes other solvents e.g. ethanol are needed 3) Ensure the ink isn't touching the solvent - you don't want it to dissolve 4) Place a lid on top of the container to stop the solvent evaporating 5) The solvent seeps up the paper, carrying the ink with it 6) Each different dye in the ink will move up the paper at a different rate so that the dyes will separate out - each dye will form a spot in a different place, 1 spot per dye in the ink 7) If any of the dyes in the ink are insoluble in the solvent used, they'll stay on the baseline 8) When the solvent has nearly reached the top of the paper, take the paper out of the beaker & leave it to dry

Measuring Energy Transfer - Method

1) Fill a polystyrene cup with the reaction mixture & measure the temperature. Record it in a table 2) Put a lid on the cup then put it in a large beaker. Measure the temperature of the mixture every 30 seconds for 5 minutes 3) Repeat this experiment but with different insulating materials inside the large beaker, wrapped around the cup e.g. cotton wool, newspaper etc 4) Compare the different temperatures for each material to find the best insulator

Making Soluble Salts Using an Insoluble Base - Method

1) Gently warm the dilute acid using a Bunsen burner, then turn off the Bunsen burner 2) Add the insoluble base to the acid a bit at a time, until no more reacts. You'll know when all the acid has been neutralised because even after stirring, the excess solid will just sink to the bottom of the flask 3) Filter out the excess solid to get the salt solution 4) To get pure, solid crystals of the salt, gently heat the solution using a water bath or an electric heater to evaporate some of the water, then stop heating it & leave the solution to cool. Crystals of salt should form which can be filtered out of the solution & then dried

List the main properties of ionic compounds

1) High melting and boiling points - many strong bonds between the ions 2) They can't conduct electricity when they're solid - the ions are held in a fixed arrangement therefore they can't pass on the electrical current. 3) They can conduct electricity when they're liquids because the ions are free to move therefore they can pass on the electrical current. 4) They dissolve easily in water - they are free to move in the solution and can carry electrical current.

Process of electrolysis in a hydrogen-oxygen fuel cell

1) Hydrogen goes into the anode compartment and oxygen goes into the cathode compartment 2) At the anode, hydrogen loses electrons to produce H⁺ ions - oxidation 3) At the cathode, oxygen gains electrons from the cathode and reacts with the H⁺ ions to make water - reduction 4) The electrons flow through an external circuit from the anode to the cathode - electric current 5) The overall reaction is hydrogen + oxygen --> water

Safety Precautions on Crystals Experiment

1) If during the experiment you spill acid on your hands, wash it off immediately 2) If you break a glass beaker, ensure everyone knows where the glass is and carefully sweep it up with a dustpan and brush 3) Ensure all long hair is tied up to prevent spilling acid on it

State three trends as you go down Group 1

1) Increased reactivity - the outer electron is more easily lost as the attraction between the nucleus and the electron decreases because the electron is further away from the nucleus 2) Lower melting and boiling points 3) Higher relative atomic mass

What do halogens form?

1) Molecular compounds - halogens share electrons via covalent bonding with other non-metals too achieves a full outer shell 2) Ionic compounds with metals - they form 1- ions called halides

Problems with Nanoparticles

1) Not yet clear whether the nanoparticles can get into your body, and if they do, whether they damage cells or not 2) Possible that when they are washed away, they might damage the environment

Testing the effect of acid concentration on the energy released during neutralisation - Method

1) Put 25cm³ of 0.25mol/dm³ of HCl & NaOH in separate beakers 2) Place the beakers in a water bath set to 25°C until they are both at the same temperature 3) Add the HCl followed by the NaOH to a polystyrene cup with a lid 4) Take the temperature of the mixture every 30 seconds & record the highest temperature 5) Repeat steps 1-4 using 0.5mol/dm³ & then 1mol/dm³ of HCl

Method on making salt crystals - Evaporation

1) Put goggles on and tie hair back. Pour sulfuric acid into a beaker 2) Using a bunsen burner, heatproof mat, tripod and gauze, heat the acid until it just starts to boil 3) Off the heat, stir some copper oxide into the acid using a stirring rod. 4) Continue to add a little bit more after each addition has dissolved until there is excess copper oxide at the bottom of the beaker and the acid has turned blue 5) Put filter paper into a filter then put that into a conical flask - filter the solution into the conical flask 6) Once filtered, pour the solution into a petri dish and leave alone overnight until salt crystals have formed

Fractional Distillation - Method

1) Put your mixture in a flask & stick a fractionating column on top. Then you heat it 2) The different liquids will all have different boiling points - they'll evaporate at different temperatures 3) The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column 4) Liquids with higher boiling points might also start to evaporate, but the column is cooler towards the top, therefore they will only get part of the way up before condensing & running back down towards the flask 5) When the first liquid has been collected, you raise the temperature until the next one reaches the top

Titration Method

1) Rinse out the burette & pipette using distilled water - ensure every last drop is thoroughly out 2) Write the acid on one beaker and the alkali on the other. Pour the acid & alkali into their beakers 3) Fix the metal rod into the clamp stand and attach the clamp holder. Slip the burette firmly inside the holder and place the stand on a surface where the top of the burette is at eye level or below. Place a ceramic square under the burette and a plastic pot on that. Put a funnel in the burette 4) Pour 50cm³ of the acid into the burette & overshoot by 1-2cm³. Let the excess acid run out into the pot. Remove the funnel & use the laminated piece of paper to ensure the volume of acid is exactly 50cm³ 5) Use the pipette filler to fill the pipette with 50cm³ of alkali. Add it to the conical flask with some indicator. The alkali should turn pink 6) Carefully, add the acid to the alkali, swirling the conical flask to mix the solutions. As soon as the hydroxide turns colourless, stop adding the acid. Use the laminated piece of paper to identify the volume of acid added 7) Record your results and repeat the experiment 4 more times, or until you find 2-3 results that are within 0.2cm³ of each other. Calculate an average 8) Repeat the experiment with the average but omit the indicator

Why is a low atom economy bad?

1) The reactions use up resources very quickly 2) They make a lot of waste materials that have to be disposed of 3) The reactions are unsustainable - the raw materials will run out & the waste has to go somewhere 4) Reactions aren't usually profitable 5) Raw materials are expensive to buy 6) Waste products can be expensive to remove and dispose of responsibly

Simple Distillation - Method

1) The solution is heated. The part of the solution that has the lowest boiling point evaporates first 2) The vapour is then cooled, condensed & is collected 3) The rest of the solution is left behind in the flask

What affects the voltage of a cell?

1) The type of electrodes used 2) Concentration of the electrolyte 3) Temperature

Effects of Nanoparticles on Health

1) The way they affect the body isn't fully understood 2) Some people are worried that products containing them have been made available before the effects on human health have been investigated properly 3) We don't know what the long-term impacts on health will be 4) Many people believe that products containing nanoparticles should be clearly labelled

What trends occur as you go down Group 7?

1) They become less reactive - it's harder to gain an extra electron because the outer shell's further from the nucleus 2) They have higher melting and boiling points 3) They have higher relative atomic masses

Give three properties which are specific to transition metals

1) They can form more than one ion e.g cobalt form Co2+ 2) They are often coloured, therefore compounds which contain them are colourful e.g. potassium chromate is yellow 3) They often make good catalysts e.g. nickel based catalysts are used in the hydrogenation of alkenes

What are the three similar basic properties of metals?

1) They're strong but are malleable 2) They're great at conducting heat and electricity 3) They have high boiling and melting points

Uses of Fullerenes

1) To 'cage' other molecules - the fullerene structure forms around another atom/molecule, which is then trapped inside - used to deliver drugs into the body 2) Make good industrial catalysts due to their large surface area 3) Make good lubricants

Benefits of Nanoparticles

1) Used in sun creams - shown to be better than the materials in traditional sun creams at protecting skin from harmful UV rays 2) Give better skin coverage than traditional sun creams

Mass of a Product - Calculation

1) Write out the balanced equation 2) Work out relative formula masses of the reactant and the product you want 3) Find out how many moles there are of the substance you know the mass of 4) Use the balanced equation to work out how many moles there'll be of the other substance - that's how many moles of product will be made of this many moles of reactant 5) Use the number of moles to calculate the mass

List three properties of metals and explain how metallic structure causes each property

1)Solid at room temperature - they have very high melting and boiling points because a lot of energy is needed to break the strong electrostatic forces of attraction between the metal atoms and delocalised electrons. 2)Good conductors of heat and electricity - the delocalised electrons can carry electrical current and thermal energy through the structure. 3)Malleable - the layers of metal atoms can slide over each other

Radius of a nucleus

1/10,000 of the radius of an atom

Chlorine Half Equation

2Cl(minus) --> Cl2 + 2e(minus)

Hydrogen Half Equation

2H(plus) + 2e(minus) --> H2

Aluminium Oxide - Anode Half Equation

2O(two minus) --> O2 + 4e(minus)

What is the Avogadro constant?

6.02x10²³

What neutralises an acid?

A base (alkali)

What is an electrochemical cell?

A basic system made up of 2 different electrodes (usually metals, in order to conduct electricity) in contact with an electrolyte

What colour is iodine?

A dark grey crystalline solid or a purple vapour

What colour is bromine?

A dense, poisonous red-brown volatile liquid

What colour is chlorine?

A fairly reactive, poisonous dense green gas

What is an electrolyte?

A liquid that contains ions which react with electrodes

What is pH?

A measure of the concentration of positive hydrogen ions in the solution

How are positive ions formed?

A metal atom loses electrons

What is the product of the reaction of a Group 1 metal with chlorine?

A metal chloride salt E.g. sodium + chlorine --> sodium chloride

What is the product of the reaction of a Group 1 metal with oxygen?

A metal oxide, depending on the Group 1 metal -Lithium + oxygen --> lithium oxide -Sodium + oxygen --> sodium oxide + sodium peroxide -Potassium + oxygen --> potassium peroxide + potassium superoxide

How are negative ions formed?

A non-metal gains electrons

What type of reaction do hydrogen-oxygen fuel cells involve?

A redox reaction

What is an ore?

A rock which contains a metal that's worth extracting - there's enough of the metal in it to make it economic to extract

What is graphene?

A sheet of carbon atoms joined together in hexagons - it's one atom thick, therefore it's a 2-dimensional compound The network of covalent bonds makes it very strong Very light - added to composite materials to improve their strength but not to add weight Contains delocalised electrons - conducts electricity through the whole structure Can be used in electronics

What is the electrolyte for a hydrogen-oxygen fuel cell?

A solution of potassium hydroxide

What colour is fluorine?

A very reactive, poisonous yellow gas

Neutralisation equation

Acid + base --> salt + water

Equation with a metal carbonate

Acid + metal carbonate --> salt + water + carbon dioxide

Phenolphthalein

Acid = colourless Alkali = pink

Litmus indicator

Acid = red Alkali = blue

Methyl orange

Acid = red Alkali = yellow

Aluminium Oxide - Cathode Half Equation

Al(three plus) + 3e(minus) --> Al

What does 100% atom economy mean?

All the atoms in the reactants have been turned into useful (desired) products - the higher the atom economy, the 'greener' the process

What is one mole?

An amount of that a substance that contains an Avogadro number of particles

What happens during electrolysis?

An electric current is passed through an electrolyte which causes the ions to move towards the electrodes where they react and the compound decomposes

What is a fuel cell?

An electrical cell that's been supplied with a fuel and oxygen (or air) and uses energy from the reaction between them to produce electrical energy efficiently When the fuel enters the cell, it becomes oxidised and sets up a p.d. within the cell

What is a negative ion?

Anion

Condensing

As a gas cools, the particles no longer have enough energy to overcome the force of attraction between them, causing bonds to form between the particles At the boiling point, so many bonds have formed between the gas particles that the gas becomes a liquid

Equation for Atom Economy

Atom economy = Relative formula mass of desired products / Relative formula mass of all reactants x 100

Are metal carbonates bases or acids?

Bases

Are metal oxides and hydroxides bases or acids?

Bases

What are non-rechargeable batteries?

Batteries which contain cells which use irreversible reactions - once one of the reactants is used up, they don't produce any more charge, therefore you have to replace them E.g. alkaline batteries

What is the name of the temperature at which a liquid becomes a gas?

Boiling

What do most exothermic reactions involve?

Burning fuels

How is a battery formed?

By connecting two or more cells together in series - the voltages are combined so there is a bigger voltage overall for the battery

How were elements arranged in the early 1800s?

By their physical and chemical properties and their relative atomic mass

What is a positive ion?

Cation

What pattern is formed from carrying out paper chromatography?

Chromatogram

How can you separate substances in a mixture?

Chromatography

What are the noble gases at room temperature?

Colourless gases

Hydrogen-Oxygen Fuel Cell

Combines hydrogen & oxygen to produce nice, clean water and release energy

Examples of exothermic reactions

Combustion Neutralisation Many oxidation reactions

Equation for Concentration (g/dm³)

Concentration (g/dm³) = Mass of solute (g) / Volume of solvent (dm³)

Equation for Concentration (mol/dm³)

Concentration (mol/dm³) = Number of moles of solute (mol) / Volume of solvent (dm³)

How can you reverse a reaction in a rechargeable cell?

Connecting the cell to an external electric current

What is crude oil a mixture of?

Different length hydrocarbon molecules

What causes the charge difference (voltage) in an electrochemical cell?

Different metals react differently with the same electrolyte

Describe the structure of diamond

Each carbon atom forms four strong covalent bonds in a very rigid giant covalent structure.

Describe the structure of graphite

Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised electron.

How are columns arranged?

Elements with similar properties

What is bond breaking?

Endothermic process - energy is supplied to break existing bonds

What happens at the same temperature & pressure?

Equal numbers of moles of any gas will occupy the same volume

Who discovered that the plum pudding model was wrong?

Ernest Rutherford

Examples of weak acids

Ethanoic acid Citric acid Carbonic acid

Which method of separation is useful to separate a soluble solid from a liquid?

Evaporation or Crystillisation

What is bonding formation?

Exothermic process - energy is released when new bonds are formed

What are titrations?

Experiments that allow you to find the volumes needed for two solutions to react together completely

Which method of separation is useful to separate an insoluble solid from a liquid?

Filtration

How do you fix the problem of a low atom economy reaction?

Find a use for the waste products - come up with a reaction that gives useful 'by-products' rather than useless ones

How do you convert mol/dm³ to g/dm³?

Find the concentration in mol/dm³ then convert the concentration using the equation: mass = moles x Mr

What are titrations used for?

Finding out exactly how much acid is needed to neutralise a quantity of alkali - or vice versa

Why are conventional fuels bad?

For vehicles (e.g. petrol), they have a finite supply and they're very polluting

Which method of distillation separates liquids with similar boiling points?

Fractional distillation

Oxidation =

Gain of oxygen Loss of electrons

What is air a mixture of?

Gases, mainly nitrogen, oxygen, carbon dioxide and argon

What's the difference between the reactivity of Group 1 and transition metals?

Group 1 metals are much more reactive than transition metals

Symbol equation of neutralisation

H(positive) + OH(negative) --> H2O

Exothermic reactions

Heat energy is given out to the surroundings during a chemical reaction. The temperature increases

Endothermic reactions

Heat is taken in from the surroundings during a chemical reaction. The temperature decreases

What are the products of the reaction of a Group 1 metal and water

Hydrogen gas and a metal hydroxide E.g. sodium + water --> sodium hydroxide + hydrogen

Change of Mass - Decrease

If the mass decreases, it's probably because one of the products is a gas and all the reactants are solids, liquids or aqueous Before the reaction, all the reactants are contained in the reaction vessel If the vessel isn't enclosed, then the gas can escape from the reaction vessel as it's formed It's no longer contained in the reaction vessel, so you can't account for its mass - the total mass of the stuff inside the reaction vessel decreases

Change of Mass - Increase

If the mass increases, it's probably because one of the reactants is a gas that's found in the air (e.g. oxygen) and all the products are solids, liquids or aqueous Before the reaction, the gas is floating around in the air - it's there, but it's not contained in the reaction vessel, so you can't account for its mass When the gas reacts to form part of the product, it becomes contained inside the reaction vessel - so the total mass of the stuff inside the reaction vessel increases

Explain why graphite can conduct electricity

It contains delocalised electrons which can carry electrical charge

Why do industrial processes need a high percentage yield?

It reduces waste and costs

Describe the structure of a crystal of sodium chloride

It's a giant ionic lattice. The positive sodium and negative chlorine ions form a closely packed regular arrangement and there are very strong electrostatic forces of attraction between the oppositely charged ions.

Why is Buckminsterfullerene a good lubricant?

It's shaped like a hollow ball, thus it can roll

Reduction =

Loss of oxygen Gain of electrons

Reaction of Metal with Water

Metal + Water --> Metal Hydroxide + Hydrogen

What do halogens exist as?

Molecules - pairs of atoms

What are fullerenes?

Molecules of carbon, shaped like closed tubes or hollow balls - the carbon atoms are arranged in hexagons but also pentagons & heptagons

What do noble gases exist as?

Monatomic gases - single atoms not bonded to each other

Cathode

Negative electrode Positive ions move towards it Electrons are gained Reduction happens

What do alkalis form in water?

Negative hydroxide ions

What type of ion do elements from Group 7 form?

Negative ions

Who devised an experiment that proved the existence of the neutron?

Niels Bohr

In real life, do you ever get a 100% yield?

No - some product or reactant always gets lost along the way

Are the noble gases flammable?

No - they're non-flammable

Why is the mass conserved during a chemical reaction?

No atoms are created and no atoms are destroyed

Can an ionic solid be electrolysed?

No, because the ions are in fixed positions and can't move

What are halogens?

Non-metals in Group 7 with coloured vapours

Problems of getting a 100% yield - Problem 1

Not all reactants react to make a product - in reversible reactions, the products can turn back into reactants, so the yield will never be 100%

Equation for Number of Moles

Number of moles (mol) = Mass (g) of an element/compound / Mr of the element/compound

Where are the non-metals on the periodic table?

On the right hand side

What happens at room temperature & pressure?

One mole of any gas occupies 24dm³

How many products do the highest atom economy reactions have?

Only one product - the lower the number of products, the higher the atomy economy is likely to be

How many types of atoms do elements contain?

Only one type

Why are some chemical reactions irreversible at the electrodes?

Over time, the reacting particles get used up and turned into products of the reaction - once any of the reactants are used up, the reaction can't happen, therefore no electricity is produced If the products can't be turned back into reactants, the cell won't be recharged

Formation of a metal ore =

Oxidation

What are the most common ores?

Oxides and sulfides

What are nanoparticles?

Particles that have a diameter between 1 nm and 100 nm - these are the smallest particles that contain only a few hundred atoms

What are coarse particles?

Particles that have a diameter between 2,500 nm and 10,000 nm - also known as dust

What are fine particles?

Particles that have diameter between 100 nm and 2,500 nm

Formula for Percentage Mass

Percentage Mass of an Element in a Compound = Relative Atomic Mass (Ar) x Number of atoms of that element / Relative Formula Mass (Mr) of the compound x 100

Equation for Percentage Yield

Percentage Yield = mass of product actually made (g) / Maximum theoretical mass of product (g) x 100

Describe the structure of a polymer

Polymers are long chains of repeating units joined together to make a long molecule. Between the atoms are strong covalent bonds.

What are the electrodes for a hydrogen-oxygen fuel cell?

Porous carbon with a catalyst

What kind of ions do metals form?

Positive

Anode

Positive electrode Negative ions move towards it Electrons are lost Oxidation happens

What do acids form in water?

Positive hydrogen ions

What type of ion do elements from Group 1 form?

Positive ions

Reactivity series

Potassium Sodium Lithium Calcium Magnesium Aluminium CARBON Zinc Iron Tin Lead HYDROGEN Copper Silver Gold Platinum

Metals that react with water out of the RS

Potassium, sodium, lithium and calcium

Reaction profiles - endothermic

Products are at a higher energy than the reactants

Reaction profiles - exothermic

Products are at a lower energy than the reactants

What subatomic particles does the nucleus contain?

Protons and neutrons

What are redox reactions?

REDuction and OXidation happen at the same time (REDOX)

Extraction of a metal =

Reduction

What is silicon dioxide?

Sand. Each grain of sand is one giant structure of silicon and oxygen.

What is simple distillation used for?

Separating out a liquid from a solution E.g. separating pure water from seawater

Name three states of matter

Solid, liquid and gas

What are compounds?

Substances containing two or more different elements that are chemically bonded together

What are mixtures?

Substances containing two or more different elements that are not chemically bonded together

Examples of strong acids

Sulfuric acid Hydrochloric acid Nitric acid

Equation for surface area to volume ratio

Surface area to volume ratio = surface area / volume

What is concentration?

The amount of a substance in a certain volume of a solution

What is the amount of product directly proportional to?

The amount of limiting reactant

What is the yield?

The amount of product you get - the more reactants there are, the higher the yield will be

What is atom economy?

The atom economy (atom utilisation) of a reaction tells you how much of the mass of the reactants is wasted when manufacturing a chemical and how much ends up as useful products

What is the trend in boiling point as you go down Group 0?

The boiling points increase

What happens in an electrochemical cell?

The chemical reactions between the electrodes & the electrolyte set up a charge difference between the electrodes If the electrodes are connected by a wire, the charge is able to flow & electricity is produced A voltmeter can be connected to the circuit to measure the voltage of the cell

Why will the electrolyte affect the size of the voltage in a cell?

The different ions in solution will react differently with the metal electrodes used

What is metallic bonding?

The electrons in the outer shell of a metal atom are delocalised. There are strong forces of electrostatic attraction between the positive metal ions and the negative electrons. These forces of attraction hold the atoms together in a regular structure.

What is the activation energy?

The energy needed to start the reaction It is the minimum amount of energy the reactants need to collide with each other and react

How are the group number and the number of electrons in the outer shell of an element related?

The group number tells you how many electrons are in the outer shell of an element. E.g. sodium is in Group 1 therefore it has 1 electron on its outer shell

Explain why simple molecular compounds typically have low melting and boiling points

The intermolecular forces between the atoms are very weak, therefore it takes only a small amount of energy to break them apart.

What is relative atomic mass?

The mass number which refers to the element as a whole

How do acids react?

The positive hydrogen ions react with other substances

What is electrolysis?

The process by which ionic substances are broken down into simple substances using electricity

What happens if the concentration of positive hydrogen ions is higher?

The rate of reaction will be faster, therefore strong acids will be more reactive than weak acids of the same concentration

What is the relative formula mass?

The relative atomic masses of all the atoms in the molecular formula added together

What is the mass of one mole of atoms of a substance equal to?

The relative formula mass of that substance

What is nanoscience?

The science that investigates the uses & properties of nanoparticles

Problems of getting a 100% yield - Problem 2

There might be side reactions - the reactants sometimes react differently to how you expect They might react with gases in the air, or impurities in the reaction mixture, which forms extra products other than the ones you want

What happens when you add more reactant?

There will be more reactant particles to take part in the reaction, therefore more product particles

Why does the boiling point of noble gases increase as you move down the group?

There's an increase in the number of electrons in each atom leading to greater intermolecular forces between them which to be overcome

Examples of endothermic reactions

Thermal decomposition

What do weak acids do in solution?

They don't fully ionise in solution - only a small proportion of acid particles dissociate to release positive hydrogen ions

What is the charge of the ions that halogens form when they react with metals?

They form negative ions

What do strong acids do in water?

They ionise completely - all acid particles dissociate to release positive hydrogen ions

Nanotubes

Tiny carbon cylinders formed from fullerenes Ratio between length & diameter is very high Conduct electricity & thermal energy High tensile strength - don't break when stretched Used for nanotechnology - used in electronics or to strengthen materials without adding much weight e.g. tennis racket frames

Why did Mendeleev leave gaps in his Table of Elements?

To ensure that elements with similar properties stayed in the same groups. The gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be

Why are reactants added in excess?

To ensure that the limiting reactant is used up

What's the difference between the hardness of Group 1 and transition metals?

Transition metals are harder, denser and stronger than Group 1 metals

What's the difference between the melting points of Group 1 and transition metals?

Transition metals have higher melting points than Group 1 metals

Do nanoparticles have a high or low surface area to volume ratio?

Very high surface area to volume ratio - the surface area is very large compared to the volume, therefore, they make good catalysts

What is the relative mass of an electron?

Very small

Simple Molecular Structures

Very strong covalent bonds Very weak intermolecular forces Most are liquids & gases at room temperature The bigger the molecule, the stronger the intermolecular forces Don't conduct electricity - no delocalised electrons or ions as they're not charged

Equation for Volume of Gas

Volume of gas (dm³) = Mass of gas (g)/Mr of gas x 24

What does acid strength tell you?

What proportion of the acid molecules ionise in water

Freezing

When a liquid cools, the particles have less energy, so move around less There's not enough energy to overcome the attraction between the particles, so more bonds form between them At the melting point, so many bonds have formed between the particles that they're held in place - the liquid becomes a solid

Boiling

When a liquid is heated, the particles will gain even more energy, making them move faster - weakens and breaks the bonds holding them together At the boiling point, the particles have enough energy to break their bonds - the liquid becomes a gas

Describe how an ionic bond forms

When a metal and a non-metal react together, the metal loses its one electron on its outer shell to form a positively charged ion. This one electron is gained by the non-metal to complete its outer shell, forming a negative ion.

Melting

When a solid is heated, the particles gain more energy which causes them to vibrate - weakens the forces that hold the solid together At the melting point, the particles will have enough energy to break free from their positions - the solid turns into a liquid

When is a reactant limiting?

When it's completed used up in a reaction before the rest and causes the reaction to stop

Explain why alloys are harder than pure metals

When two metals are mixed together, both of their atoms are different sizes which causes a disruption in the neat layers of metal atoms. This makes it more difficult for the layers to slide over each other.

Describe how covalent bonds form

When two non-metals bond together, they share electrons to make covalent bonds. The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces - this makes covalent bonds very strong.

Problems of getting a 100% yield - Problem 3

When you filter a liquid to remove solid particles, you nearly always lose a bit of liquid or a bit of solid If you want to keep the liquid, you'll lose the bit that remains with the solid and filter paper If you want to keep the solid, some of it'll get left behind when you scrape it off the filter paper You'll always lose a bit of material when you transfer it from one container to another - some always gets left behind on the inside surface of the old container

Can a molten ionic compound be electrolysed?

Yes, because the ions can move freely and conduct electricity

What is the problem with simple distillation?

You can only use it to separate things with very different boiling points - if the temperature goes higher than the boiling point of the substance with the highest boiling point, they will mix again

Metals that don't react with water out of the RS

Zinc, iron and copper

State Symbols

solid - s liquid - l gas - g aqueous - aq