Chemical Equations A Balancing Act

Propane has three atoms of carbon and eight atoms of hydrogen Propane has three atoms of carbon and eight atoms of hydrogen. What is propane's chemical formula? This screen will disappear in 3 minutes. 8 7 9 20 6 10 4 2 3 180 5 30 130 120 140 70 50 60 40 170 160 150 80 110 90 100 1 Seconds Remaining.

C3H8

List the elements in this compound: H2SO4 How many atoms of each element are in the compound? 9 8 10 20 30 7 5 2 3 4 180 6 40 130 140 50 120 70 60 1 160 170 110 150 80 100 90 Seconds Remaining:

H2SO4 Hydrogen – 2 atoms Sulfur – 1 atom Oxygen – 4 atoms

What does a chemical equation tell us? 9 8 10 20 30 7 5 2 3 4 180 6 40 130 140 50 120 70 60 1 160 170 110 150 80 100 90 Seconds Remaining:

Chemical equations tell us how many atoms or molecules react with each other and how much of a substance is needed to react properly with another.

A student wrote the following equation: 4Al + 3O2 2Al2O3 – Write a sentence to describe what occurs in this reaction. 9 8 10 20 30 7 5 2 3 4 180 6 40 130 140 50 120 70 60 1 160 170 110 150 80 100 90 Seconds Remaining:

In this reaction, aluminum reacts with oxygen to form 2Al2O3.

What do coefficients & subscripts show us in chemical formulas? 9 8 10 20 30 7 5 2 3 4 180 6 40 130 140 50 120 70 60 1 160 170 110 150 80 100 90 Seconds Left:

6 – H, 3 – S, 12 - 9 Coefficients – the number of molecules Subscripts – the number of atoms No number is understood to be “1” 3H2SO4 = H2SO4 6 – H, 3 – S, 12 - 9 H2SO4 = 2 – hydrogen 1 – Sulfur 4 – Oxygen subscript coefficient

Identify the reactants, products, subscripts, and coefficients in this chemical equation: 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2 9 8 10 20 30 7 5 2 3 4 180 6 40 130 140 50 120 70 60 1 160 170 110 150 80 Seconds Remaining: 100 90

Carbon Dioxide + Water + Light energy → Glucose + Oxygen 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2 Coefficients Subscripts Carbon Dioxide + Water + Light energy → Glucose + Oxygen Reactants: CO2 H2O light Products: C6H12O6 O2

CHEMICAL EQUATIONS A chemical equation describes what happens in a chemical reaction. The equation identifies the reactants (starting materials) and products (resulting substance) For example, we know that hydrogen gas and oxygen gas can react to form water. A chemical equation for the production of water is; H2 + O2 –› 2H2O Reactants = 2 atoms of Hydrogen & 2 atoms of Oxygen Product = 2 water molecules

Law of Conservation of Mass Matter cannot be created nor destroyed; there are no more atoms at the end of a chemical reaction than there were at the beginning.

Law of Conservation & Balancing Chemical Equations When you react 2 molecules of hydrogen gas (H2) with 1 molecule of oxygen gas (O2), you will get 2 molecules of water (H2O): 2 H2 +  O2 –› 2 H2O Notice in the equation above that you started with 4 atoms of hydrogen and 2 atoms of oxygen, and you ended with 4 atoms of hydrogen and 2 atoms of oxygen.

Balancing Chemical Equations