1. How do you know when a chemical reaction has occurred?
Chemical Reactions
How do you know when a chemical reaction has occurred?

2. REVIEW
During a physical change, a substance changes its form but remains the same substance.
A chemical change turns one or more substances into different substances that usually have different properties.

3. Chemical Reactions
What is a chemical reaction?

4. A chemical reaction is a system of chemical changes that involves the breaking and reforming of chemical bonds to create new substances.
Write definition of chemical reaction in notes

5. Products and reactants
In chemical reactions, you start with reactants.
They are combined to make the new substances called products.
Write definition of reactants and products in otes

6. Reactants
Products

7. In chemical reaction, NO new atoms are created or destroyed, just rearranged!
Copy into notes

8. Conservation of Mass
The mass of the reactants equals the mass of the products since the atoms are the same.
Copy into notes

9. Alka-Seltzer and Water
Do the demo
H2O + Na(HCO3)    CO2  +  NaOH  +  H2O

10. Chemical Equations
A chemical equation is a way to show the exact numbers of atoms and compounds in a chemical reaction.
The arrow shows the direction the reaction goes, from reactants to products.
Use the printed notes
Reactants
Products

11. Numbers in equations

12. 2H2O
Means H2O H= 4 O=2

13. Atoms in baking soda
NaHCO3
Na= 1
H= 1
C= 1
O= 3
Sodium bicarbonate

14. Atoms in carbon dioxide
CO2
C= 1
O= 2

15. Chemical reactions must be balanced

16. Balanced or not?
The reaction combines hydrogen and oxygen molecules.

17. 10.1 Chemical equations
Count the atoms to see if there are the same number of each type of atom on the reactant and product sides of the equation.
not balanced.

18. Yes, it follows conservation of mass because it’s balanced
Balanced or not?
O= 2 O=2
H= 4 H=4
Yes, it follows conservation of mass because it’s balanced

19. On the molecular level, dissolving of a solid (like sugar) occurs when molecules of solvent interact with and separate molecules of solute

20. In chemical reaction, NO new atoms are created or destroyed just rearranged!
Copy into notes