Mixtures

Question 1

What is a mixture?

Answer 1

a substance that contains two or more substances which keep their own properties.

Question 2

What are some examples of mixtures?

Answer 2

1. soda water = Carbon dioxide and water (soft drinks e.g. sprite, coke, fanta, mountain dew)
2. Muddy water = Dirt and water
3. Sand and water = Sand and water
4. Smoke = gases and solids
5. Fog = water droplets in air
6. Smog = carbon dioxide trapped in water droplets
7. Sugar water = sugar and water

Question 3

What are two types of mixtures?

Answer 3

Solutions and suspensions

Question 4

What is a solution?

Answer 4

a mixture in which the minor component (the smaller part) is
uniformly distributed with in the major component (the larger part) and you cannot
distinguish particles of the minor component from the major component.

Question 5

What are some examples of solutions?

Answer 5

Sugar water
soda water
salt water

Question 6

What are the two components of a solution?

Answer 6

In a solution the components are called solute and the solvent.

NB: in a solution there can be many solutes but only ONE solvent.

Question 7

What is a solute?

Answer 7

(minor component(s)) – a substance that can be dissolved

Question 8

What is a solvent?

Answer 8

Solvent (major component) – a substance which dissolves other substances

Question 9

What is a suspension?

Answer 9

a substance of fine particles of a solid that are visible and suspended in a liquid in which the solid does not dissolve.

NB: Since the solid does not dissolve in the liquid it is said to be insoluble (not able to be
dissolved).

Question 10

What are some examples of suspensions?

Answer 10

Muddy water is a suspension of dirt particles in water.
Flour mixed in water.
Sand in water.

Question 11

What are 5 techniques that can be used to separate the components of a solution and suspension?

Answer 11

1. Filtration (used to separate a suspension)
2. Chromatography (used to separate a solution of dyes)
3. Decanting (used to separate both solutions and suspensions)
4. Simple distillation (used to separate a solution)
5. Evaporation (used to separate a solid (e.g. salt) from a liquid (e.g. water) to recover the
   solid only)

Question 12

What is a filtrate?

Answer 12

the liquid obtained when the components of a suspension are separated.

Question 13

What is residue?

Answer 13

the solid remaining on the filter paper when the components of a suspension are
separated.

Question 14

Explain the process of filtration.

Answer 14

Filtration makes uses of apparatus such as filter paper, a filter funnel and a container. The filter paper is fitted into the funnel and acts as a sieve keeping back the solid particles whereas the liquid is allowed to pass through the filter paper. The part of the mixture that stays behind in the filter paper is called the residue and that part that passes through the filter paper is called the filtrate.

NB: We will be specifically focusing on Filtration and you are expected to be able to label a filtration diagram and describe the process. (study diagram in notes & watch videos.)

Question 15

When can you use the process of filtration?

Answer 15

This method is used to separate liquids from both suspended and settled solids. The solid must not be soluble in the liquid.

Question 16

What is the solid phase of paper chromatography?

Answer 16

Paper is the solid phase (the phase that does not move)

Question 17

What is the mobile phase of paper chromatography?

Answer 17

The Solvent (solution or liquid) is the mobile phase (the phase that moves)

Question 18

What does the process of paper chromatography do to ink?

Answer 18

The ink is a mixture that is separated into its pure components

Question 19

What do the colours shown in paper chromatography represent?

Answer 19

The colours seen are the individual pure substance

Question 20

When is decanting used?

Answer 20

This is when we want to separate solutions like:
sand in water
oil in water (solution with different densities)

Question 21

What happens to the oil in a mixture of oil and water?

Answer 21

Oil floats on water in an oil and water mixture

Question 22

What happens to the sand in a mixture of sand and water?

Answer 22

while sand sinks to the bottom in a sand and water mixture.

Question 23

What is the apparatus used in decanting?

Answer 23

The apparatus we use is called a separating funnel.

Question 24

What happens to the lower density element of a mixture?

Answer 24

It floats

Question 25

What happens to a higher density element in a mixture?

Answer 25

It sinks

Question 26

Describe the process of decanting.

Answer 26

We place the two substances in the separating funnel and shake it well and then place it to stand on vertically so that both substances in the mixture can clearly distinguished before separating.

Question 27

When is distillation used?

Answer 27

This method of separation is used for a solution whose components have large individual boiling points. Such that when one reaches being a vapor (gas state), the other one remains in the liquid state.

Question 28

What is an example of a solution that can be separated using distillation?

Answer 28

This is a good technique to separate a solution such as saltwater (seawater), to recover both the pure salt and pure water.

Question 29

What is the apparatus used in evaporation?

Answer 29

The apparatus used is a called an evaporating dish.

Question 30

What is a solution that evaporation can be used for?

Answer 30

This is a method of separation that is used to separate salt from water in a saltwater mixture, where we are only interested in recovering the salt.

Question 31

Describe the process of evaporation.

Answer 31

Here heat is needed to cause the water (solvent particles like water) to evaporate off and leave the solid (e.g. salt crystals behind). To speed up the process we may increase the heat using a heat source like a Bunsen burner.