Chemical Changes
| Physical Change | Chemical Change |
|---|---|
| No new substances formed | New substances formed |
| Atoms not rearranged | Atoms rearranged |
| Reversible using separation techniques | Irreversible |
| Heat energy taken in or given out | Heat energy taken in or given out |
Different Types of Chemical Changes interactions
| Mixing | Neutralisation | ||||
|---|---|---|---|---|---|
| Heat | Thermal Decomposition | ||||
| Oxygen | Oxidation | Combustion | Cellular Respiration | Rusting | Browning of Apples |
| Light | Photosynthesis | X-Ray | |||
| Electricity | Electrolysis | Electroplating |
^^Neutralisation^^
- Process when an acid reacts with and alkali
- Salt and Water is formed
- Eg. Hydrochloric acid(acid) reacts with sodium hydroxide(alkali) to form sodium chloride and water
^^Thermal Decomposition^^
- Process where a substance is broken down into two or more simpler substances when heated
- Eg. Copper(II) carbonate is heated to form copper(II) oxide and carbon dioxide
^^Oxidation^^
- Process where a substance reacts with oxygen
^^Browning^^
- Exposed surface of apples turn brown due to reaction with oxygen in the air
^^Combustion^^
- Process where a substance reacts with oxygen in the presence of heat, releasing a lot of it in the process
- One or more new substances produced
- Eg. Charcoal(carbon) in a barbecue pit burns in oxygen to form carbon dioxide
- Eg. Combustion of methane gas(natural) to generate electricity in power plants which forms carbon dioxide and water- If combustion is incomplete, produces carbon monoxide, carbon dioxide and water
^^Cellular Respiration^^
- Process where living cells of plants and animals take in oxygen to release the energy stored in glucose
- To provide cells with energy to grow and reproduce
- Carbon dioxide and Water are produced
^^Rusting^^
- Process where iron reacts with oxygen in the presence of water vapour
^^Photosynthesis^^
- Process where green plants make food in the presence of light
^^Electrolysis^^
- Chemical decomposition of substances with the passage of an electric current
^^Electroplating^^
- Process where a substance is coated with a metal with the passage of an electric current
Acids and Alkalis
- Acids- substance that dissolves in water and dissociates (break up) to give hydrogen ions (h+) which is responsible for the properties of an acid
- Alkali- substance that dissolves in water and dissociates (break up) to give hydroxide ions (OH-) which is responsible for the properties of an alkali
| ==Acid== | %%Alkali%% |
|---|---|
| pH value less than 7 | pH value of more than 7 |
| tastes sour | tastes bitter and feels slippery |
| turns blue litmus paper red | turns red litmus paper blue |
| no effect on red litmus paper | no effect on blue litmus paper |
| turns universal indicator solution to (orange) or red (red) | turns universal indicator solution to blue (weak) or purple (strong) |
| corrosive if concentrated | corrosive if concentrated |
| conducts electricity when dissolved in water due to free moving hydrogen ions | conducts electricity when dissolved in water due to free moving hydroxide ions |
pH scale
| 0-3 | Strong acid |
|---|---|
| 4-6 | weak acid |
| 7 | neutral |
| 8-10 | weak alkali |
| 11-14 | strong alkali |
@@C H O M@@
| Acids react with… | ^^C^^arbonates | ^^H^^ydroxides and ^^O^^xides | ^^M^^etals |
|---|---|---|---|
| Forms? | Salt, Carbon dioxide gas and water | Salt and Water | Salt and Hydrogen Gas |
| Example | Calcium Carbonate reacts with hydrochloric acid to form calcium chloride, water and carbon dioxide | Sodium Hydroxide and nitric acid reacts to form sodium nitrate and water | |
| Example | Potassium Carbonate reacts with sulfuric acid to form potassium sulfate, water and carbon dioxide | Sodium Oxide and nitric acid reacts to form sodium nitrate and water | |
| How to test for it | Bubble the gas through limewater (calcium hydroxide) in which a white precipitate will form | Insert a lighted splint into the test tube of hydrogen gas in which the lighted splint will extinguish with a ‘pop’ sound |