ASSESSMENT 17TH APRIL REVISION

Question 1

Arrangement and movement of states of matters

Answer 1

ARRANGEMENT:
. Particles in a solid are
tightly packed together, (SOLID)
in neat rows and close.
MOVEMENT:
. They vibrate rapidly around
a fixed position.
ARRANGEMENT:
. Particles in liquid are randomly
spaced, mostly touching.
MOVEMENT:
. The particles slide & collide
over each other for having small (LIQUID)
space in between.
ARRANGEMENT:
.Particles in gas are spread out,
low interaction in between.
MOVEMENT: (GAS)
. They move in all directions very
rapidly, frequently colliding with
each other.

Question 2

.How can you compress gas but not liquid?
. Why does liquid take up the shape of its container?

Answer 2

In GAS, particles are very far out from each other meaning there’s huge amount empty space between them which can be reduced by increasing pressure on it. IN LIQUID though, the particles are still packed close together meaning there’s less empty space.

. Liquids take up the shape of container because their particles are loosely packed together and also have less force of attraction in between which does not allow the molecules to remain at their place.

Question 3

Describe the changes of states of matter

Answer 3

Adding energy to solid => particles gaining energy and breaking down to form liquid (Melting)
Adding energy to liquid=> gaining energy and breaking down more to move more rapidly and form gas (Boiling)
Removing energy from gas => particles losing energy and move less rapidly to form liquid (Condensing)
Removing energy from liquid => Freezing/Solidifying

SOLID => GAS = SUBLIMATION
GAS => SOLID = DEPOSITION

Question 4

Give the definitions of following words:
- Solute
- Solvent
- Solution
- Saturated

Answer 4

Solute : The substance which is being dissolved.
Solvent : The fluid where the solute is being dissolved.
Solution : The mixture of solute + solvent. It can be either soluble or insoluble.
Saturated solution : The solution that contains the maximum amount of solute that’s capable of dissolving at a particular temperature. In it, no more solute can be dissolved at that given temp.

Question 5

What is the word for ‘maximum amount of solute dissolved in 100g of water at a given temperature’?

Answer 5

Solubility, /100g of water.

Question 6

What is the definition of pure and impure substances?

Answer 6

Pure substance - substance having no other material mixed in it.
. Pure substances have fixed melting and boiling points, whereas impure substances have a range of points.
. More impurity an object has, higher the boiling point and lower melting point.

Question 7

How to calculate the Rf value?

Answer 7

Distance moved by solvent front

Question 8

How do pure and impure substances apply to the chromatograms?

Answer 8

A pure substance will have a SINGLE spot on the chromatography paper.
An impure substance/mixture will have more than spot.

Question 9

Explain the ways of separating mixtures.

Answer 9

Distillation - Separates liquid from a solution
Fractional distillation - Separates mixtures of miscible liquids.
Separating funnel - Separates mixtures of immiscible liquids.

Evaporation - Separates a solute from a solution.
Filtration - Separates solid from liquid.
[Residue] substance that gets trapped
[Filtrate] fluid that is obtained

Paper Chromatography - Separate mixtures of coloured substances or inks.

Question 10

IMPORTANT FACTS ABOUT A CHROMATOGRAM

Answer 10

• The most soluble dye will be farthest away from the starting spot (with the water)
• When two objects have their ink spots travelling the same distance, those inks are identical.
• They can be used to identify different unknown dyes.