The document discusses physical and chemical changes. A physical change alters a substance's physical properties but does not create a new substance, such as melting ice. A chemical change produces a new substance through a chemical reaction, like cooking or burning. Chemical reactions have reactants that interact to form products, and there are four main types of chemical reactions: combination, breakdown, precipitation, and combustion. The rate of a chemical reaction can be affected by factors like surface area, temperature, and concentration of reactants. Catalysts are substances that increase the rate of reactions without being used up in the process.

1. Physical and Chemical Change Year 8 Science Ms Alexander

2. Physical Change ? Definition of a PHYSICAL CHANGE A physical change occurs when a a substance changes but no new substance is formed. Example of a PHYSICAL CHANGE? Melting of ice to water

3. Chewing my breakfast

4. Chemical Change ? Definition of a CHEMICAL CHANGE A chemical change occurs when a new substance is formed. Another word for Chemical Change is CHEMICAL REACTION. Example of a CHEMICAL REACTION? Cooking a cake

5. Burning toast

6. What are products and reactants?

7. Chemical Reactions ? There are 4 types of CHEMICAL REACTIONS Combination

8. Break-down

9. Precipitation

10. Combustion

11. Last Class What pracs did you do? What happened? What was the result?

12. Combination Reaction ? Definition: A combination reaction occurs when two reactants combine to form a single new substance

13. Breakdown Reaction ? Definition: A Breakdown reaction occurs where one substance breaks up to a number of smaller ones.

14. Decomposition in your compost heap!

15. Start with: Plant material--> C

16. Precipitation Reaction ? Definition: A reaction were a solid is produced when two solutions are added together.

17. Combustion Reaction ? Definition: A combustion reaction occurs when a compound reacts with oxygen to produce carbon dioxide and energy.

18. Example Fireworks, a Bunsen burner, Human respiration

19. Compare and Contrast ? Create a Venn Diagram. Use the words: products, reactant, synthesis, decomposition