1. Chapter 6
Chemical Reactions

2. Main Idea Chemical reactions allow living things to: Grow Develop
Reproduce
Adapt

3. Reactants and Products
A chemical reaction is the process by which atoms or groups of atoms in a substance are reorganized into different substances.
During chemical reactions, chemical bonds are broken and formed.

4. Chemical Equations
Chemical formulas describe the substance in the reaction and arrows indicate the process of change.
Reactants are the starting substance, on the left side of the arrow.
Products are the substances formed during the reaction, on the right side of the arrow.
Reactants → Products

5. Chemical Equations In the reaction below:
Glucose (C6H12O6) and Oxygen = Reactants
Carbon dioxide and Water = Products
C6H12O6 + O2 → CO2 + H2O

6. Balancing Equations The law of conservation of mass states:
Matter cannot be created or destroyed.
This means that the number of atoms of each element on the reactant side must be equal to the number of atoms of the same element on the product side.

7. Balancing Equations
The below equation is NOT balanced.
C6H12O6 + O2 → CO2 + H2O
C = 6 C = 1
H = 12 H = 2
O = 8 O = 3
We must have equal number of atoms of each element on the same side.

8. Balancing equations Balanced form: C6H12O6 + O2 → CO2 + H2O
C = 6 C = 6
H = 12 H = 12
O = 18 O = 18

9. Energy of Reactions
The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction.
Lets say we need 10 J of energy for a reaction to occur.
If we have 10 J, 11 J or higher the rxn will occur.
If we have 9.9 J, 9 J or lower the rxn will not occur.

10. Energy Diagram This reaction is exothermic It released heat energy
The energy of the product is lower than the energy of the reactants

11. Exothermic RXN
Usually releases energy in the from of light and heat
An exothermic reaction is a chemical or physical reaction that releases heat.
It gives out energy to its surroundings.
The energy needed for the reaction to occur is less than the total energy released.

12. Energy Diagram This reaction is endothermic It absorbed heat energy
The energy of the product is higher than the energy of the reactants.

13. Endothermic RXN
Describes a process or reaction in which the system absorbs energy from its surroundings in the form of heat.
melting ice cubes
melting solid salts
evaporating liquid water
cooking an egg
baking bread