1. Today’s Agenda…. Bellringer: Turn to page 601 and read about changes of state. Edit Bellringers from yesterday Review changes and reactions

2. State Changes Physical change The substance remains the same It can be reversed Moo Glue? A state change? – It is not a state change because you are putting two liquids together and they react to form a solid – The solid is a new substance – This cannot be easily reversed

3. Review What is a chemical change? – Creates a new substance – Not easily reversed What are some clues that a chemical change has taken place? – Change in color, odor, sound – Release or absorb heat or light – Produce a gas or solid

4. Chemical Reactions When you observe a chemical change, a chemical reaction has taken place Let’s look at some examples!

5. Iron Rusting Look at the before and after. Why does the balloon look the way it does? What has happened?

6. Baking Soda and Vinegar Look at the before and after. Why does the balloon look the way it does? What has happened?

7. Roasting a Marshmallow

8. An Apple Rotting

9. Baking Bread Why is this not just a change of state?

10. What do these all have in common? Law of conservation of mass During a chemical OR physical change matter cannot be created or destroyed.

11. Law of Conservation of Mass Chemical reactions are represented by symbols and formulas The symbols come from the periodic table The numbers tell you how many particles are in the substances Examples: –O2–O2 –H20–H20 – 3CaCl – 2CO 2 – If there is a large number in front you must multiply the small number by that one!

12. Law of Conservation of Mass In a chemical reaction you have products (what you start with) and reactants (what you end up with). Reactants are on the right, products are on the left The mass must be the same on both sides The number and type of particles must be the same on both sides

13. Law of Conservation of Mass If my reactants have a mass of 45 grams, what will the mass of my products be? If I have 10 particles that make up my reactants, how many particles will make up my products?

14. Example: Iron Rusting 4Fe + 3O 2 2Fe 2 O 3 None of the particles are lost, they are just rearranged to form new substances!