Chemical reactio

1. change An endothermic change transfers energy from the surroundings.
4. A chemical reaction in which substances react with oxygen to form oxides.
8. A material that burns to transfer useful energy.
9. of mass In a chemical reaction, the total mass of reactants is equal to the total mass of products. This is conservation of mass. Mass is conserved in chemical reactions and in physical changes.
12. A substance that is made in a chemical reaction.
15. The chance of damage or injury from hazard.
16. A possible source of danger.
17. symbol equation In a balanced symbol equation, chemical formulae represent the reactants and products. The equation shows how atoms are rearranged, and gives the relative amounts of reactants and products.

2. Some fuels are non-renewable. They form over millions of years, and will one day run out.
3. A chemical reaction in which a substance reacts quickly with oxygen and gives out light and heat.
5. A chemical reaction in which a compound breaks down to form simpler compounds and/or elements.
6. reaction A change in which atoms are rearranged to create new substances.
7. change A change that is reversible, in which new substances are not made. Examples of physical changes include changes of state, and dissolving.
8. fuel A fuel made from the remains of animals and plants that died millions of years ago. Fossil fuels include coal, oil, and natural gas.
10. change An exothermic change transfers energy to the surroundings.
11. equation A way of representing a chemical reaction simply. The reactants are on the lefts of an arrow, and the products are on the right. The arrow means reacts to make.
13. A variable that can only have whole-number values.
14. A starting substance in a chemical reaction.