CHEMISTRY- CHEMISTRY OF THE ELMENTS

Thermal decomposition

another way of making carbon dioxide is by heating a metal carbonate. Thermal decomposition is when a substance breaks down into simpler substances when heated. Copper (II) carbonate is a green powder that will easily decompose to form carbon dioxide and copper (II) oxide. The equation is: CuCO3(s) ----> CUO(s) + CO2(g) collect the gas using downward delivery method.

calcium

brick red flame

Magnesium in air

burns with a bright light flame, to form white powder, magnesium oxide, slightly alkaline when dissolved in water

sulfur in air

burns with a pale blue flame and produces sulfure dioxide, this is acidic when dissolved in water

Test for Cations

chemical tests for positive ions

Hydrochloric acid + metal

chlorides

Groups

columns of a periodic table, elements in the same group have similar chemical properties, this is because they have the same number of electrons in their outer shell. The properties of elements gradually change as you go down a group.

Increasing Carbon dioxides link to climate change

correlation between increasing co2 levels and climate change (heating up of the earth's atmosphere- global warming). Although the airs temp varies naturally, theres a scientific consensus that the rising levels in the earths temperature are due to carbon dioxide. Global warming is a type of climate change but can also lead to other changing weather patterns e.g. changing rainfall patterns and sea levels rising

Test for Ammonia

damp red litmus paper turns blue when presented with ammonia. The litmus paper needs to be damp so the ammonia can dissolve.

making carbon dioxide with calcium carbonate

dilute acid reacts with calcium carbonate to produce carbon dioxide. Calcium carbonate (marble chips) are put in the bottom of a flask and dilute HCL is added, this reacts with the calcium carbonate to produce calcium chloride, carbon dioxide and water. Collect the CO2 in a gas syringe using downward delivery.

Carbon dioxide uses

fizzy drinks: it is slightly soluble and dissolves into drinks when under pressure, which makes a slightly acidic solution due to the formation of carbonic acid. Fire extinguisher: carbon dioxide is more dense than air so it sinks onto the flames and stops the oxygen getting to the fire, used when water extinguishers aren't safe.

GROUP 1- REACTIVITY

group 1 elements become more reactive as they move down the group. We can see the reactivity by seeing how long it takes for the element to react with water, the more reactive the less time it takes. As the atomic number increases, so does the reactivity. Atoms lose electrons more easily as we move down the group, as the force of attraction between them and the nucleus is less.

carbon in air

has an orangey yellow flame and produces carbon dioxide gas, this is slightly acidic when dissolved in water

Making oxygen

hydrogen peroxide decomposes to form water and oxygen, the reaction is really slow, but the rate of reaction will be increased with some manganese IV oxide, the catalyst speeds up the reaction without being used up itself, the oxygen can be collected over water using a gas syringe.

RUST

iron and steel corrode to make rust, which only happens when iron is in contact with both oxygen and water. The reaction that takes place is an oxidation reaction, the iron gains oxygen to form iron (III) oxide and the result is hydrated iron (III) oxide, which we call rust. iron + oxygen + water ----> hydrated iron (III) oxide (rust).

potassium

lilac flame

metals and water

metal + water = metal hydroxide + hydrogen

Displacement

more reactive metal displaces a less reactive metal. This is because a more reactive metal will displace a less reactive metal from its oxide, because it will bond more strongly to the oxygen

Test for pure water

Boils at 100 degrees celcius, freezes at 0 degrees celsius.

Prevention of Rust

painting/coating with plastic or oiling/greasing or the sacrificial method, which involves placing a more reactive metal with the iron, which means that the oxygen will react with the sacrificial method instead of with the iron. Zinc is usually used as a sacrificial metal. Zinc is more reactive than iron, so the zinc will react with the oxygen instead. When zinc is sprayed onto an object, it is called galvanising, or big blocks of zinc can be nailed onto ships hulls or on underground iron pipes.

REACTIVITY SERIES

potassium sodium lithium calcium magnesium aluminium zinc iron copper silver gold

Iron (III), fe3+

reddish brown precipitate

REACTION OF METALS

acid + metal = salt + hydrogen, the more reactive the metal, the more quick the reaction, very reactive metals will react explosively. Hydrogen is tested by the squeaky pop.

sulphuric acid + metal

sulphates

Test for anions

test for negative ions

Periods

the rows in a periodic table the properties of the elements change as you go along a period

downward delivery collection

this is used to collect gases that are heavier than air (e.g. CO2, CL2)

upward delivery collection

this is used to collect gases that are lighter than air (e.g. H2)

Sodium

yellow orange flame

Non metals

On the right of the periodic table, poor conductors of electricity. Non metal oxides are acidic, they dissolve in water to form a solution with a pH of less than 7.

Nitrogen

78%

Gases in the atmosphere

78% nitrogen, 21% oxygen, 1% argon, 0.04% CO2

Carbon dioxide

0.04%

Argon

1%

Oxygen

21%

Sodium hydroxide metal oxides method

Add a few drops to metal hydroxide solution to a SOLUTION of your mystery compound if there is a coloured insoluble precipitate formed then it is one of these:

Test for Carbonates

Add dilute hydrochloric acid to your test sample. If carbonates are present, then carbon dioxide will be released

Group 0

All these elements are called the noble gases, and include the elements helium, neon and argon. They are INERT as they have a full outer shell of electrons, meaning that they are not desperate to lose or gain electrons.

Copper (II), Cu 2+

BLUE precipitate

Bromide ion

CREAM precipitate of SILVER BROMIDE

Test for Chlorine

Chlorine bleaches damp litmus paper, it may turn red before (chlorine is acidic)

Flame test for metal ions

Clean a platinum wire loop by dipping in some HCL and then holding it in a flame. Once it burns without any colour, you can dip the loop into any metal sample and then put back into the flame:

Test for Water

Copper (II) sulphate crystals can be used as a test for water. When copper (II) sulphate binds to water, it forms blue crystals. When this is heated, the water evaporates, leaving white anhydrous copper sulphate powder.

Lithium

Crimson-red flame

Metals

Elements on the left, conduct electricity. Metal oxides are basic metals, meaning they will neutralise acids. They will dissolve to from solutions with a pH of more than 7.

Iron (II), fe2+

Sludgy green precipitate

Sodium hydroxide precipitation reactions

Some METALS form a coloured precipitate when added to NaOH. These metal oxides are insoluble and precipitate out of solution with a characteristic colour.

Test for sulphates

Sulphate ions form a white precipitate. When testing for a sulphate, add dilute HCL followed by barium chloride solution, (BaCl2). A white precipitate of barium sulphate means that the original compound was a sulphate. The hydrochloric acid is added before the experiment in order to remove any carbonate or sulphite ions, as they would also produce a precipitate.

Carbon dioxide as a greenhouse gas

The temperature of the earth is balanced between the heat it gets from the sun and the heat it radiates back into space. gases in the atmosphere like carbon dioxide, methane and water vapour naturally act like and insulting layer- greenhouse gases. They absorb most of the heat that would normally be radiated back into space and re-radiate it in all directions. Human activity affects the amounts of co2 in the atmosphere (deforestation: fewer trees=less co2 absorbed due to photosynthesis and Burning fossil fuels: carbon locked up in these sources is being released as CO2) Carbon dioxide is being released faster than the rate it is being removed.

GROUP 1- The alkali metals

They all react in a similar way with water (e.g. when lithium, sodium and potassium are put in water they react vigorously) when they react with water they create a metal hydroxide solution, which is alkaline. The reaction of the alkali metals with water also produces hydrogen, which is why we see fizzing.

Test for Halides (Cl-, Br- and I-)

To test for Cl-, Br- and I-: chloride, bromide and iodide ions, add dilute nitric acid (HNO3), followed by silver nitrate solution. We add the nitric acid to remove any sulphite or carbonate ions before the test)

Chloride ion

WHITE precipitate of SILVER CHLORIDE

test for oxygen

When a glowing splint is placed in a test tube of oxygen, it will relight

Iodide ion

YELLOW PRECIPITATE of SILVER IODIDE