Chapter 2 | Energy And Chemical Changes

Question 1

What is a chemical change?

Answer 1

It’s a change in the nature and characteristic properties of matter ;

This change happens through chemical reactions.

Question 2

What to remember about chemical reaction equations?

Answer 2

AB + Energy —> A + B
(Means energy was absorbed)

AB —> A + B + Energy
(Means energy was released)

• Energy on the left means it was absorbed
• Energy on the right means it was released

Question 3

How do you find chemical changes?

Answer 3

1. Release of gas
2. Large change in heat
3. Generation of light
4. Change in colour
5. Formation of a precipitation

Question 4

Give an example of release of a Gas:

Answer 4

Baking Soda and Vinegar
Release Of A Gas :

-Bubbles forming indicate chemical reaction

Question 5

Give an example of emission/absorption of heat:

Answer 5

Wood combusting (oxidizing):

-Heat released indicates chemical reaction

Question 6

Give an example of emission of light:

Answer 6

Wood combusting (oxidizing)

-Light released indicates chemical reaction

Question 7

Give an example in change in colour:

Answer 7

Change in Colour
Litmus Paper

-Litmus paper changes colour when it reacts with acids or bases

Question 8

Give an example of a formation of a precipitate:

Answer 8

CO² (Carbon Dioxide) and Limewater
Formation of a precipitate

-Limewater reacts with the CO² to produce a solid precipitate

Question 9

What type of change is ice melting and why is it that change?

Answer 9

It’s a physical change ;

It’s only absorbing energy which makes it melt, it’s characteristics stay the same

Question 10

What type of change is a nail rusting?

Answer 10

It’s a chemical change (oxidation), it’s generating a new substance (the rust) from oxygen.

Iron (Fe) + Oxygen (O) = Iron Oxide (Fe2O3)

Question 11

Name the parts of a chemical equation:

Answer 11

H² + Cl² —> 2HCl

• The substances in the left side of the equation are called Reactants
• The substances on the right side of the equation are called Products

Question 12

Name the different types of chemical reactions :

Answer 12

1. Synthesis
2. Decomposition
3. Oxidation
4. Precipitation

Question 13

How does Synthesis work?

Answer 13

2 or more reactants combine to form a new product.

A + B = AB

(Less complicated to more complicated)

Question 14

How does Decomposition work?

Answer 14

Decomposition: A Product separates to form 2 or more reactants.

AB —> A + B

(More complicated to less complicated)

Question 15

How does Oxidation work?

Answer 15

It’s a chemical reaction relating to oxygen, oxidation can be slow or fast

Slow:

• Bananas browning
• Rust forming

Fast:

1. Combustion:
   - Word burning
   - Gasoline igniting

Question 16

How does precipitation work?

Answer 16

2 solutions are combined to produce a solid precipitate:

Reactant X + Reactant Y —> Solid + Product Z

Example: limewater

Ca(OH) + CO² —> CaCO + H²O

Question 17

In a chemical equation what are the THINGS that ARE reactants and products?

Answer 17

Anything that is not Energy in a chemical equation is a particle;

They are either atoms or molecules