1. Chemical Reactions
Chapter 10 Section 1

2. Vocabulary Word
chemical reaction: process where atoms rearrange to form different substances
examples: digestion of food, productions of fibers (cotton/wool), fuel to power vehicles

3. All chemical reactions…
have two parts:
Reactants = the substances you start with
Products = the substances you end up with
The reactants will turn into the products.
Reactants ® Products

4. Products
Reactants

5. Mass is conserved!!!!!!!!!
The number of atoms of each element at the beginning and the end of a chemical reaction must be the same.
The total mass also must be conserved. The total mass of the reactants (in grams) must equal the total mass of the products.

6. In a chemical reaction A reaction can be described several ways:
#1. In a sentence every item is a word
Copper reacts with chlorine to form copper (II) chloride.
#2. In a word equation some symbols used
Copper + chlorine ® copper (II) chloride

7. Symbols in equations
the arrow () separates the reactants from the products (arrow points to products)
Read as: “reacts to form” or yields
The plus sign = “and”
(s) after the formula = solid: Fe(s)
(g) after the formula = gas: CO2(g)
(l) after the formula = liquid: H2O(l)

8. Symbols used in equations
(aq) after the formula = dissolved in water, an aqueous solution: NaCl(aq) is a salt water solution
­ used after a product indicates a gas has been produced: H2↑
¯ used after a product indicates a solid has been produced: PbI2↓

9. Vocabulary Word
chemical equation: statement using chemical formulas to describe the identities and relative amounts of reactants and products in a chemical reaction

10. Vocabulary reactant: starting substance in a chemical reaction
product: substance formed in a chemical reaction

11. Symbols used in equations
double arrow indicates a reversible reaction (more later)
shows that heat is supplied to the reaction
is used to indicate a catalyst is supplied (in this case, platinum is the catalyst)

12. Balancing Chemical Equations

13. The Skeleton Equation Uses formulas and symbols to describe a reaction
but doesn’t indicate how many; this means they are NOT balanced
All chemical equations are a description of the reaction.

14. Write a skeleton equation for:
Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (III) chloride and hydrogen sulfide gas.
Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water.

15. Now, read these equations:
Fe(s) + O2(g) ® Fe2O3(s)
Cu(s) + AgNO3(aq) ® Ag(s) + Cu(NO3)2(aq)
NO2(g) N2(g) + O2(g)

16. Symbols used in Chemical Equations (Please copy entire slide into notes)

17. Balancing Chemical Equations
Chemical reactions must be balanced, because the law of conservation of mass says that matter cannot be created or destroyed.

18. Vocabulary
coefficient: number written in front of a reactant or product indicating the smallest number of particles in a chemical reaction

19. Conservation of Mass:
The number of atoms of each element must be the same after the reaction as there was before the reaction.
The total mass also must be conserved. The total mass of the reactants (in grams) must equal the total mass of the products.