EXTRA

Question 0

Why do many ionic compounds dissolve easily in water?

Answer 0

Because water is a POLAR SOLVENT

Question 1

Why do most covalent compounds not dissolve in water?

Answer 1

Because they are RELATIVELY NON-POLAR (e.g. Nail vanish)

Question 2

What is the name of the polar protein that makes up our nails?

Answer 2

Keratin

Question 3

When is centrifugation used as a separation technique?

Answer 3

Separating solid particles from liquid

E.g. Separation of blood components in hospitals (the blood cells are collected at the lower half of the tube)

E.g. Separation to obtain cream from milk in dairies

Question 4

When is chromatography used as a separation technique?

Answer 4

Separating/identifying similar substances

E.g. Separating different pigments in ink

Question 5

When is distillation used as a separation technique?

Answer 5

Separating a solvent from a solution

E.g. Making pure drinking water from sea water

E.g. production of alcoholic spirits in industry

Question 6

When is fractional distillation used as a separation technique?

Answer 6

Separating liquids which mix completely

E.g. Separating different fractions in crude oil

Question 7

When is evaporation/crystallisation used as a separation technique?

Answer 7

Separating a soluble solute from a solution

E.g. Separating salt from seawater

Question 8

When is filtration used as a separation technique?

Answer 8

Separating an insoluble solid from a fluid

E.g. Making clear water from muddy water

Question 9

Define:

Suspension

Answer 9

Particles held in a fluid (liquid or gas)

Question 10

Define:

Filter

Answer 10

The material that causes the separation

Question 11

Define:

Filtrate

Answer 11

The fluid that has passed through the filter

Question 12

Define:

Residue

Answer 12

The material left on the filter

Question 13

Why is centrifugation used for separation instead of filtration?

Answer 13

Sometimes the solid particles are so small that they can pass through the tiny holes of the filter paper.

centrifugation forces the denser particles to the end of a centrifuge tube leaving the liquid as a layer on top which can be poorer off.

Question 14

What is the salt in seawater?

Answer 14

Sodium chloride

Question 15

Define:

immiscible liquids

Answer 15

Liquids which settle and remain as two distinct layers when mixed.

E.g. Water and oil

Question 16

Define:

Miscible liquids

Answer 16

When two liquids are mixed, they mix so well that they are indistinguishable from each other

E.g. When Alcohol and water are mixed

They can be separated using fractional distillation because of their different boiling points

Question 17

How can the gases in air be separated?

Answer 17

Fractional distillation can be used to separate the gases in air.

The gas enters through a filter and then goes through a compressor, a separator, and a heat exchanger.

The water and carbon dioxide are removed early in the process because they would freeze in the heat exchanger.

Question 18

Complete:

The more soluble the pigment, the ________ it will be on the chromatography paper.

Answer 18

The more soluble the pigment, the HIGHER it will be on the chromatography paper

Question 19

Why do solids melt when they are heated up?

Answer 19

The forces of attraction between the particles are no longer strong enough to hold them together as a solid.

Question 20

What is a DIATOMIC GAS?

Answer 20

In a diatomic gas, each molecule consists of two atoms. (E.g. Oxygen, chlorine, hydrogen)

Question 21

What are the 3 ways which particles can move in?

Answer 21

Translation - straight lines of movement, unless the particles collide or are acted upon by gravity.

Rotation - the turning of a particle around a fixed point (e.g. The planets)

Vibration - the rapid movement of particles from side to side, about a fixed point. (When the particles are too close together to freely move)

Question 22

How many times will a gas particle as room temp. Usually collide with the particles around it?

Answer 22

Around 1 million times per second

Question 23

Why is no energy lost when particles collide?

Answer 23

The collisions are ELASTIC.

Question 24

Define:

Sublimation

Answer 24

Sublimation is the change of state when a solid changes directly to a gas (or vice versa) without passing through the liquid state.

This is a rare process.

Substances which sublime: iodine, camphor, and carbon dioxide.

Heating= sublimation

Cooling= reverse sublimation

Question 25

Can water only evaporate at it’s boiling point?

Answer 25

No!

It can evaporate at room temperature too.

Question 26

How does a catalyst work? (4)

Answer 26

• speeds up reaction
• by reducing activation energy
• activation energy is needed to break chemical bonds
• the lower the activation energy the more particles have enough energy for their bonds to be broken in order to react

Question 27

Complete: higher temperature means the particles move faster, and there are therefore more _______________

Answer 27

Collisions PER TIME

Question 28

Complete: higher concentration means more particles __________, and therefore more _______________.

Answer 28

higher concentration means more particles PER VOLUME, and therefore more COLLISIONS PER TIME.