Chemical reactions

4. the cells in your body that contain thousands of biological catalysts
10. a way to show a chemical reaction using symbols
12. matter can enter or escape from its surroundings
13. the minimum amount of energy needed to start a chemical reaction
14. when matter during a chemical reaction matter is not created or destroyed
16. the new substances that form from a chemical change
18. when two elements in compounds swap places
20. when two or more elements or compounds combine to make a more complex substance

1. any change that alters the form or appearance of any substance but does not change it into another substance
2. a change in matter that produces one or more substances
3. a number placed in front in a chemical formula in an equation
5. a material used to decrease the rate of a chemical reaction
6. matter cannot leave or enter
7. the substance that undergoes the chemical changes
8. a reaction that absorbs heat and feels cold
9. when a complex substance breaks down into simpler products
11. the amount of a substance in a given volume
15. increases the rate by lowering the activation energy needed
17. a solid that forms from liquids during a chemical reaction
19. a reaction that releases heat and feels hot