Y8: Balancing Equations

• Chemistry
• Lower Secondary (Key Stage 3)

Y9: Balancing Equations and chemical formula

.

In a balanced equation the number of atoms of each element is the same on each side of the arrow.

These are hydrogen atoms

a

This + sign means "reacts with" or "bonds with"

b

These are oxygen atoms

C

These are water molecules

d

Here we see 4 hydrogen (white) on the left and 2 oxygen (red). On the right we still see 4 Hydrogen and 2 oxygen. 

These are hydrogen atoms

a

This + sign means "reacts with" or "bonds with"

b

These are oxygen atoms

C

These are water molecules

d

All that changed was the arrangement of the hydrogen and oxygen. 

These are hydrogen atoms

a

This + sign means "reacts with" or "bonds with"

b

These are oxygen atoms

C

These are water molecules

d

Is this equation balanced?

1. Yes it all the same either side of the arrow
2. No there's more blues on the left than the right.

How can I balance this equation

1. Double the products (right) and the pinks (left)
2. Split the blues and throw one away (left)

Is this equation balanced?

1. Yes
2. No

How many oxygen atoms are there in each of these substances?

Substance	Oxygen Atoms
O
HNO
C H O
MgO
CO
MgCO

2

2

3

3

6

12

6

1

2

2

3

3

6

Is this equation balanced? (Count the colour dots)

1. No
2. Yes

Is this equation balanced?

1. Yes there's one red and 4 blue on each side
2. No they are in different arrangements.

To balance an equation we can multiply any of the existing substances until the number of atoms is equal.

I have 1 more blue here than on the right

I have one more orange here than on the right

If I double up this molecule the equation will balance.

Drag up one box (one molecule) so that the  equation will be balanced

Drag one box showing one molecule to balance the  equation.

Drag two boxes (move two molecules) to balance the equation.

Add two molecules to balance the  equation.

Add three molecules to balance the  equation.

Add two molecules to balance the  equation.

Naming compounds

One oxygen atom = monoxide

Two oxygen atoms = dioxide

Three oxygen atoms = trioxide.

Monoxide

Dioxide

Trioxide

Carbon dioxide

Not carbon dioxide

Drag the names into the balanced equation.

Carbon x 2

Oxygen x 2 

Carbon monoxide x 2 

The red is oxygen, the white is hydrogen

1 red 2 white

One carbon Two oxygens

1 black, 2 red

This has 3 red (oxygens) 2 white (Hydrogens) 1 black (Carbon)

This double arrow means the reaction can go forwards and backwards.

This reaction is reversible.

What does this double arrow mean?

1. Two way street
2. Reversible reaction

How can we tell this reaction is balanced?

1. There are different atoms bonded together
2. There's the same number of atoms on both sides of the arrow.

What is the first step in balancing a chemical equation?

1. Identifying the catalyst
2. Measuring the volume of the reactants
3. Counting the number of atoms of each element
4. Determining the reaction rate

Hydrogen

Oxygen

Water

How many of each do we need to make it balance?

Just this pair

One more pair

One more molecule