1. Chapter 6 – 1 Chemical Reactions
The Nature of Chemical Reactions

2. Chemical Reactions Types of chemical reactions: Growing Ripen Decay
Burn
Digestion

3. Chemical Reactions Chemical reactions change substances
Sugar, water, yeast, heat  Bread
Chemical Reaction

4. Chemical Reaction
Chemical reaction - change in which one or more substances are converted into new substances
Example – baking a cake

5. Signs of Chemical Reactions
Signs a chemical reaction may have occurred:
Light
Heat
Sound

6. Chemical Reactions
Reactant – substance or molecule that participates in a reaction
Product – substance that forms in reaction

7. Chemical Reaction Gas in a car Reactants: Isooctane C8H18 Oxygen O2
Products:
Carbon dioxide CO2
Water H20

8. Chemical Reactions
The products and reactants contain the same types of atoms.
Rearranged as bonds are broken and formed.
Mass is always conserved

10. Antoine Lavoisier
Antoine Lavoisier - established that the total mass of the products always equals the total mass of the reactants
French Chemist
Father of Modern Chemistry

11. Conservation of Mass
The mass of the candles and oxygen before burning is exactly equal to the mass of the remaining candle and gaseous products.

13. Energy and Reactions All chemical reactions release or absorb energy.
Takes the form of:
Heat
Light
Sound
Electricity

14. Energy and Reactions When chemical reactions take place -
Some chemical bonds in the reactants are broken
Requires energy
In order for products to be produced, new bonds must form.
Bond formation releases energy.

15. Chemical Energy
Chemical Energy – energy released when a chemical compound reacts to produce new compounds

16. Exothermic Reaction
Exothermic Reaction - The energy given off in a reaction is in the form of heat
Heat Release
Examples –
Burning wood or exploding dynamite

17. Endothermic Reaction
Endothermic Reaction - The energy needed is in the form of heat
Heat absorption
Some reactions are so endothermic that they can cause water to freeze.

18. Endothermic Reactions
Photosynthesis is endothermic