Chemical Changes

Monroe 1-9-09

What are the parts to a chemical formula?

Coefficient

Atoms

Subscripts

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of compound. It always goes on the front.

Subscripts ~

Element

Compound

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of the compound. It always goes in the front.

Subscripts ~ Tells the number of atoms in the compound. Subscript means “below writing”.

Element ~

Compound

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of substance.

Subscripts ~ Tells the number of atoms in the compound

Element ~ Tells the type of atom in the compound

Compound

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of substance.

Subscripts ~ Tells the number of atoms in the compound

Element ~ Tells the type of atom in the compound

Compound ~ Tells what combination of atoms, chemically combined, you are looking at.

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of substance.

Subscripts ~ Tells the number of atoms in the compound

Element ~ Tells the type of atom in the compound

Compound ~ Tells what combination of atoms, chemically combined, you are looking at.

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of substance.

Subscripts ~ Tells the number of atoms in the compound

Element ~ Tells the type of atom in the compound

Compound ~ Tells what combination of atoms, chemically combined, you are looking at.

C8H10N4O2

This is a compound

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of substance.

Subscripts ~ Tells the number of atoms in the compound

Element ~ Tells the type of atom in the compound

Compound ~ Tells what combination of atoms, chemically combinded, you are looking at.

C8H10N4O2

This is a subscript

What are the parts to a chemical formula?

Coefficient ~ Tells the number of units of substance.

Subscripts ~ Tells the number of atoms in the compound

Element ~ Tells the type of atom in the compound

Compound ~ Tells what combination of atoms, chemically combined, you are looking at.

C8H10N4O2

This is an element

What do they tell us? They tell us how different chemicals will combine with each other.

What do they tell us? They tell us how different chemicals will combine with each other.

O2 + H2 H2O + heat

What is very, very wrong with this equation?

What do they tell us? They tell us how different chemicals will combine with each other.

O2 + H2 H2O + heat

It is NOT balanced.

Oxygen 2 1

Hydrogen 2 2

What do they tell us? They tell us how different chemicals will combine with each other.

O2 + H2 H2O + heat

O2 + 2H2 ---> 2H2O + heat

Oxygen 2 2

------------------------------------------------------------

Hydrogen 4 4

(Always multiply the coefficient and the subscript)

Some important things to remember.

1. The stuff on the left is the reactants

2. The stuff on the right is the products

3. The total amount of stuff on the left MUST equal the amount of stuff on the right, because of the law of conservation of mass.

Some important things to remember.

1. The stuff on the left is the reactants

2. The stuff on the right is the products

3. The total amount of stuff on the left MUST equal the amount of stuff on the right, because of the law of conservation of mass.

4 g of Hydrogen + 32 g Oxygen = 36 g Water

O2 + 2H2 ---> 2H2O + heat

Balancing equations

1. Solid magnesium burns with gaseous oxygen to make solid magnesium oxide.

2. Step one is to write out the sentence with chemical symbols, according to what actually happens.

Mg (s) + O2(g) --> MgO(s) + energy

Step two is to choose coefficients that balance the number of atoms on each side, but never, never ever change the subscripts. If you change the subsript, you are saying that something else is being made.

2Mg (s) + O2 (g) --> 2MgO(s)

If there is no coefficient, or subscript, it is a “one”.

Hydrogen gas burns with oxygen to make liquid water, and excess energy. Hydrogen gas and oxygen gas are always O2 and H2.

Hydrogen gas burns with oxygen to make liquid water, and excess energy. Hydrogen gas and oxygen gas are always O2 and H2.

H2(g) + O2(g) ---> H2O(l) + energy

Hydrogen peroxide (H2O2) liquid decomposes into oxygen gas and water, if energy is added to the equation.

Hydrogen peroxide (H2O2) liquid decomposes into oxygen gas and water, if energy is added to the equation.

H2O2 + energy --> H2O + O2

Hydrogen peroxide (H2O2) liquid decomposes into oxygen gas and water, if energy is added to the equation.

H2O2 + energy --> H2O + O2

2H2O2 + energy --> 2H2O + O2

Butane gas (C3H8) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.

Butane gas (C3H8) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.

C3H8 + O2 ---> CO2 + H2O + energy

Butane gas (C3H8) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.

C3H8 + 5O2 ---> 3CO2 + 4H2O + energy

Photosynthesis is when sugar, C6H12O6 and O2 combine to make carbon dioxide and water.

C6H12O6 + O2--> CO2 + H2O

Photosynthesis is when sugar, C6H12O6 and O2 combine to make carbon dioxide and water.

C6H12O6 + 6O2--> 6CO2 + 6H2O