Chemical Reactions

Homework Read pages: 61-63 Worksheet: Word Equations and Reactions

2

Describing Chemical Change

In a chemical reaction, one or more substances (reactants) change into one or more different substances (products).Reactants Products

Chemical reactions involve chemical changes.

Describing chemical changeReactants change into products

Bonds are broken Atoms re-arrange New bonds are formed

Atoms themselves are neither created nor destroyed!

Describing Chemical Change

What happens when you combine baking soda and vinegar ? describe some of the changes.

In aqueous solution, acetic acid reacts with sodium bicarbonate to produce sodium acetate, carbon dioxide and water.

Describing Chemical Change

sodium bicarbonate

+

aqueous

acetic acid

sodium acetate

+

carbon dioxide

+

water

Symbol Explanation

+ Separates two or more reactants or products

Yields - separates reactants from products

→;←;↔ Reversible reaction

(s); (l); (g) solid, liquid or gas

(aq) Aqueous solution – a substance dissolved in water

Heat supplied

Platinum used as a catalyst

heat

→

→Pt

Chemical Equations The physical state of the substances can

be indicated by placing a symbol in parenthesis after the formula

C12H24(s) + O2(g) CO2(g) + H2O(g)

(s) For solid, (l) for liquid, (g) for gas, and (aq) for an aqueous solution.

Heat

Chemical Equations What would the skeleton equation be

for the following: Sulfur burns in oxygen to produce sulfur

dioxide.

S(s) + O2(g) Heat SO2(g)

Chemical Equations What would the skeleton equation be for

the following: When solid potassium is added to water,

hydrogen gas and aqueous potassium hydroxide are produced

K(s) + H2O(l) H2(g) + KOH(aq)

Homework Read 61-63 Reactions 8 and Balancing Chemical

Equations

Balancing Chemical Equations

Rules for Balancing Equations

1. Determine the correct formula of all reactants and products

2. Write reactant on the left and products on the right side of the arrow.

3. Count the total number of atoms of each element on each side.

Balancing Chemical EquationsRules for Balancing Equations4. Balance the elements one at a time by using

coefficients – DO NOT CHANGE SUBSCRIPTS

5. Check each atom or polyatomic ion to make sure the equation is balanced

6. Make sure all coefficients are the lowest possible ratio that balances

Let’s see how it is done…

Balancing Chemical EquationsBalance the following equations:

SO2 + O2 SO3

Fe2O3 + H2 Fe + H2O

P + O2 P4O10

Al + N2 AlN

Balance the following equations:2SO2 + O2 2SO3

Fe2O3 + 3H2 2Fe + 3H2O

4P + 5O2 P4O10

2Al + N2 2AlN

More Practice…

Balancing Chemical Equations