Lesson 1: Physical/ Chemical changes

Question 1

What is a physical change?

Answer 1

Physical changes are reversible changes where no bonds are being broken and made.
No new substance is formed.
Structure of particles rearranged

Question 2

What is a chemical reaction?

Answer 2

Bonds are broken and made to make new substances.

Hard to reverse

Question 3

What are the signs of a chemical reaction?

Answer 3

Temperature change (taken in, taken out) 
Colour change 
Gas given off (effervescence) 
Odour change 
Precipitate formed

Question 4

What is a precipitate?

Answer 4

Precipitate: solid that suspends in a liquid.

- Will not dissolve.

Question 5

What does the conservation of mass state?

Answer 5

Mass is neither created or destroyed by a chemical or physical reaction.
Mass of reactants = mass of products

Question 6

What is an indicator?

Answer 6

An indicator is a substance that changes colour depending on the pH of the solution it is in.

Question 7

What is litmus paper?

Answer 7

Litmus paper is an indicator that will either turn red (acid) or blue (alkali.)

Question 8

What is the pH scale?

Answer 8

The pH scale is a measure of acidity and alkanity from 0-14.

Question 9

Why is universal indicator better than litmus paper?

Answer 9

• It shows the strength of acids and alkalis.