Unit 3

Question 1

Purpose of decantation

Answer 1

A quick method to remove much denser insoluble solid from a liquid.
—> to obtain a clear liquid OR remove unwanted liquid from the solid

Question 2

Application of filtration

Answer 2

Face masks: to protect the airways of people working in dusty environment
—> to separate dust from air
Vacuum cleaner

Question 3

Evaporation

Answer 3

Conversion of a liquid to vaporous at any temperature below the boiling point of the liquid

Question 4

How to show a saturated solution is obtained?

Answer 4

Remove a drop of the solution with a glass rod on the microscopic slide. Observe any crystals forms quickly on the cool glass.

Question 5

How to show a saturated solution is obtained?

Answer 5

Remove a drop of the solution with a glass rod on the microscopic slide. Observe any crystals forms quickly on the cool glass.

Question 6

Suggest two reasons why nichrome is a suitable material to use the wire in the flame test.

Answer 6

1) have a high melting point
2)does not colour the flame and is very unreactive

Question 7

Suggest two reasons why nichrome is a suitable material to use the wire in the flame test.

Answer 7

1) have a high melting point
2)does not colour the flame and is very unreactive

Question 8

Why is a luminous flame not suitable for the flame test?

Answer 8

Difficult to observe the colour produced by the substance under test.
—> luminous flame may mask the result