Chemistry

2. – A combination of different substances that are not chemically bonded (e.g. air, saltwater).
5. Reaction – A process where atoms rearrange to form new substances.
7. of Mass – Atoms are not lost or created in a chemical reaction; they are rearranged.
8. Bond – A force that holds atoms together in molecules or compounds.
9. – A tiny particle with a negative charge that moves around the nucleus.
12. Change – A change where a new substance is formed (e.g. burning, rusting, baking). Usually irreversible.
13. of Chemical Change – Gas produced, colour change, temperature change, precipitate (solid) forms.
14. – A pure substance made of only one type of atom (e.g. gold, oxygen).
15. – A substance that speeds up a chemical reaction without being used up.
18. new substances formed by the chemical reaction
19. – A particle in the nucleus with no charge (neutral).
20. substances present at the start of a chemical reaction, used up during the reaction.

1. – The new substances made in a chemical reaction.
2. – Two or more atoms bonded together (e.g. O₂, H₂O).
3. – The starting substances in a chemical reaction.
4. Change – A change where no new substance is formed (e.g. melting ice, dissolving sugar). Usually reversible.
6. – A substance made when two or more different elements are chemically bonded (e.g. CO₂, NaCl).
7. Theory – Reactions happen when particles collide with enough energy.
10. of Reaction – How fast a chemical reaction happens.
11. – The centre of the atom that contains protons and neutrons.
16. – The smallest building block of matter; makes up everything.
17. Effect – Heating particles gives them more energy → more collisions → faster reactions.
18. – A particle in the nucleus with a positive charge.