1. Chemical Reactions

2. Standards
Conservation of Matter and Stoichiometry 3a. Students know how to describe chemical reactions by writing balanced equations

3. Objectives
Identifying the reactants, products and other parts of chemical equations
Write word equations from a chemical reaction description
Write chemical equations from word equations
Identify and include solid (s), liquid (l), gas (s), and/or aqueous (aq) in chemical equations
Identify and write the seven diatomic elements

4. Definitions
Chemical equation: a precise detailed accounting of both the identities and amounts of reactants consumed and products formed in a reaction
Identities: all participants in reaction get named
Amounts: how much is specified in equation, (moles)
Reactants: the starting substance(s) in a chemical reaction
Product: substance(s) formed in a chemical reaction

5. Definitions
Word equation: description of a reaction without using chemical formulas
Reactants: what you start with
Products: what is made

6. Definitions
Catalyst: a substance that speeds up a reaction without being used up; enzymes good example
Aqueous: dissolved in water (aq)
Diatomic: two of the same atom naturally bound together

7. Writing a Word Equation
Hydrogen reacts with oxygen to form water
Word Equation:
hydrogen + oxygen → water
Chemical Equation:
H2 + O2 →H2O
Reactants
Product

8. Diatomic Elements
Diatomic: two of the same atom naturally bound together
Hydrogen and Oxygen and some others exist bound together. They are always found as a pair, so when you write them write them as H2, O2.

9. Diatomic Elements “7”

10. Write the Word & Chemical Equation…
Calcium metal reacts with chlorine gas to produce calcium chloride
Calcium + chlorine → calcium chloride
Ca + Cl2 → CaCl2

11. Write the Word & Chemical Equation…
When zinc metal reacts with oxygen gas, solid zinc oxide is formed.
Zinc + oxygen → zinc oxide
Zn + O2 → ZnO

12. Write the Word and Chemical Equation…
Carbon dioxide gas and water are produced when methane gas is burned in oxygen.
Methane + oxygen → carbon dioxide water
CH4 + O2 → CO2 + H20

13. Write the Word & Chemical Equation…
When zinc metal is placed in a solution of hydrochloric acid, hydrogen gas and a zinc chloride solution are formed.
Zinc + hydrochloric acid → hydrogen gas zinc chloride
Zn(s) + HCl (aq) → H2 (g) + ZnCl2 (aq)

14. Rules for balancing
Must have same # of each atom on both sides of the equation
Must use coefficients to balance, can not add subscripts

15. Balance the Equation
Calcium metal reacts with chlorine gas to produce calcium chloride
Calcium + chlorine → calcium chloride
Ca Cl2 → CaCl2

16. Balance the Equation
When zinc metal reacts with oxygen gas, solid zinc oxide is formed.
Zinc + oxygen → zinc oxide
Zn O2 → ZnO

17. Balance the Equation
Carbon dioxide gas and water are produced when methane gas is burned in oxygen.
Methane + oxygen → carbon dioxide water
CH O2 → CO H20

18. Balance the Equation
When zinc metal is placed in a solution of hydrochloric acid, hydrogen gas and a zinc chloride solution are formed.
Zinc + hydrochloric acid → hydrogen gas zinc chloride
Zn(s) + HCl (aq) → H2 (g) + ZnCl2 (aq)

19. WORKSHEET a

20. END