Chemistry

1. Matter cannot be created or destroyed
5. Bonds formed when atoms share electrons
8. A short way to show what elements are in a compound and how many of each there are
10. Substances that's slow down or stop chemical reactions
12. Things that come from nature
13. Substances that make chemical reactions happen faster
14. Pure substances made up of only one type of atom
16. The new substances form the chemical reaction
18. 2 or more substances that join together
19. A chemical reaction that absorbs heat energy

2. Made by people
3. A chemical reaction that releases heat energy
4. Small numbers written to show how many atoms of each element are in a compound
6. Things that make up everything around us
7. When substances change into different ones
9. Numbers written in front of chemical formulas to balance equations
11. Bonds formed by the attraction between positively and negatively charged ions
15. The substances you start within a chemical reaction
17. Heat Energy