Across
- 6. A chemical used to distinguish between acidic and alkaline solutions. Examples include phenolphthalein, litmus and methyl orange. They are also used in titration reactions to indicate the end point of the reaction by a clear colour change
- 8. A chemical reaction in which a more reactive element displaces a less reactive element from its compound.
- 10. The elements in Group 1 of the periodic table. They are typically soft and have relatively low melting points.
- 15. The increase in the temperature of the Earth’s atmosphere due to the greenhouse gases in the atmosphere trapping infra-red radiation from the surface.
- 17. The protection of iron or steel against corrosion by using a more reactive metal. Zinc is often used as a sacrificial metal. Sacrificial protection creates a physical barrier to oxygen and water, preventing corrosion of the metal.
- 19. The reaction in which an acid and a base react to form a salt and water.
- 21. A process used to protect against corrosion by coating the metal with a protective layer of zinc.
- 22. The burning of a substance in oxygen. If there is sufficient oxygen present for the substance to burn then it is called complete combustion. Energy is transferred to the surroundings as heat and light.
Down
- 1. The breaking down of a compound by heating.
- 2. The ions formed by halogen atoms by gaining an electron. They have a 1- charge. E.g. Cl-, Br- and I-.
- 3. Qualitative test used to identify metal ions (cations). Carried out by inserting a nichrome wire loop with the unknown compound on into a flame and observing the colour.
- 4. The elements in Group 7 of the periodic table. The halogens gain an electron to form halide ions with a 1- charge. Down the group the halogens get more reactive and have higher melting and boiling points.
- 5. A measure of the acidity or alkalinity of a solution ranging from 0 to 14. The pH can be measured using universal indicator solution or a pH probe.
- 7. The destruction of materials by chemical reactions with substances in the environment, e.g. rusting occurs when iron is exposed to water and oxygen.
- 9. A substance which reacts with an acid in a neutralisation reaction to form a salt and water only. Bases are known as proton acceptors.
- 11. A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis.
- 12. A change in global climate patterns largely believed to be caused by the increase in concentration of carbon dioxide in the atmosphere.
- 13. Gases in the atmosphere which maintain temperatures on Earth high enough to support life. Greenhouse gases include water vapour, carbon dioxide and methane.
- 14. A series in which metals are arranged in order of their reactivity. This can be used to predict products from reactions.
- 16. A reddish coating of iron oxide which forms on iron when it undergoes oxidation. Iron rusts when it is in the presence of oxygen and water.
- 18. Produces hydroxide ions (OH-) in aqueous solutions. They have a pH range between 7 and 14. Alkalis are soluble bases.
- 20. Produces hydrogen ions (H+) in aqueous solutions. They have a pH range between 0 and 7. Acids are known as proton donors.