1. Chapter 2 Matter and Change . 2.4 Chemical Reactions
2.1 Properties of Matter
2.2 Mixtures
2.3 Elements and Compounds
2.4 Chemical Reactions
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2. Write down 3 examples of chemical reactions.
Describing Matter
Write down 3 examples of chemical reactions.
How do you know they are chemical reactions?
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3. Signs of a Chemical Change Transfer of energy Color change
Recognizing Chemical Changes
Signs of a Chemical Change
Transfer of energy
Color change
Production of a gas
Formation of a precipitate.
Only way to know for sure is to test composition before & after!!!
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4. Transfer of energy

5. Color Change
Color Change
When a test strip is dipped in a solution, the color change is used to determine the pH of the solution.

6. Production of a Gas
Production of a Gas Bubbles of carbon dioxide form when two antacid tablets are dropped into a glass of water.

7. Precipitate Formation
In the production of cheese, a reaction causes milk to separate into solid curds and liquid whey

8. A chemical reaction is also called a chemical change.
Chemical Changes
A chemical reaction is also called a chemical change.
4Fe + 3O2  2Fe2O3
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9. A chemical reaction is also called a chemical change.
Chemical Changes
A chemical reaction is also called a chemical change.
4Fe + 3O2  2Fe2O3
Reactants  Products
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10. Mass of reactants = Mass of Products
Chemical Changes
A chemical reaction is also called a chemical change.
4Fe + 3O2  2Fe2O3
Reactants  Products
Mass of reactants = Mass of Products
223 g Fe g O2
= g Fe2O3
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11. Chemical Changes
If 4 grams of hydrogen reacts with 32 g of oxygen, how many grams of water will be produced?
2H2 + O2  2H2O
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12. Chemical Changes
When 16g of hydrogen reacts to form 144g of water, how many grams of oxygen are required?
2H2 + O2  2H2O
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13. Physical Change Chemical Change
Causes properties of a material to change, but the composition of the material does not. Breaking
Change that causes one material to change into a different material. Burning
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14. Physical Change Chemical Change
Change that causes the properties of a material to change, but the composition of the material does not.
Examples:
Cutting
Melting
Freezing
Change that causes one material to change into a different material. Examples: Burning Rotting Reacting
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15. Describing Matter
Chemical Property – characteristic that can only be observed when we attempt to change the identity of a material
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16. Physical or Chemical Property?
Blue Color Density Flammability Melting Point Reacts with acid to form Hydrogen Burns Boiling Point Hardness Luster (shininess)

17. Physical or Chemical Property?
Blue Color - physical Density - physical Flammability - chemical Melting Point - physical Reacts with acid to form Hydrogen - chemical Burns - chemical Boiling Point - physical Hardness - physical Luster (shininess) - physical

18. END OF 2.4
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