Mixtures

Question 1

Define pure substance.

Answer 1

A substance that is made up of only one type of particle. A pure substance has the same properties all the way through

Question 2

Define mixture.

Answer 2

Two or move substances with different physical properties that are mixed together

Question 3

What are physical properties?

Answer 3

Special characteristics used to describe a substance

Question 4

What are particles?

Answer 4

The tiny parts that make up substances

Question 5

All materials or substances are made up of….

Answer 5

Matter

Question 6

Matter is made up of….

Answer 6

Tiny particles

Question 7

We can classify matter as either _______ or _______

Answer 7

…a pure substance…a mixture of different substances

Question 8

Give four examples of pure substances.

Answer 8

1. Gold nugget
2. Water (h20)
3. Table salt
4. Carbon dioxide

Question 9

What happens when we mix 2 substances?

Answer 9

The particles of one substance move in between the particles of the other substance. The different particles of the mixture do not join together. The different parts of a mixture can be combined in any amounts

Question 10

What happens in some mixtures such as green beans and rice? (Properties?)

Answer 10

The substances that are mixed together keep all of their own physical properties. The properties of the beans and the properties of the rice remain the same. They are just mixed together

Question 11

What happens in some mixtures such as salt and water?

Answer 11

The properties of the mixture are a combination of the properties of the substances that were mixed.
Eg. Salt water looks like water, but it tastes like salt

Question 12

How can we separate mixtures?

Answer 12

Using physical methods. This means that we do not need a chemical reaction to separate a mixture. Because the different substances in a mixture are not joined together, we can use their different physical properties to separate them. For example, in a moxture of sand and rice, the sand and rice have different physical properties. The sand particles and the rice particles differ in size, colour and shape. The mixture can be separated by placing it in a sieve - the small sand particles pass through the sieve but the rice grains do not

Question 13

Define sieving.

Answer 13

Method in which a sieve is used to separate a mixture of solids containing different sized particles

Question 14

Define filtration.

Answer 14

Method in which a filter is uses to separate a solid from a liquid

Question 15

Define insoluble.

Answer 15

Describing a solid that does not dissolve in a liquid

Question 16

We can sort a mixture that is made up of solid particles that have different sizes, colours, textures or shapes by…

Answer 16

Hand

Question 17

What are the pros and cons of hand sorting?

Answer 17

Pros:
It is easy and cheap
Cons:
Takes a long time

Question 18

When can we use filtration?

Answer 18

To separate an insoluble solid from a liquid
Eg. A mixture of sand and water

Question 19

Difine dissolve.

Answer 19

When the particles of a solid spread between the particles of a liquid so that you can no longer tell the two substances apart

Question 20

Difine solution.

Answer 20

Mixture that consists of a solid dissolved in a liquid

Question 21

Difine solute.

Answer 21

Substance that dissolves when making a solution

Question 22

Difine solvent.

Answer 22

Liquid in a solution in which the solute dissolves

Question 23

Define evaporation.

Answer 23

Process of changing from a liquid to a gas because particles on the surface of the liquid escape into the atmosphere

Question 24

When can magnets be used?

Answer 24

A mixture of substances in which one of the substances is magnetic and the other not, can be separated using this difference in their properties.
Eg. Magnets are used in recycling to recover magnetic substances from domestic waste

Question 25

How can evaporation be used?

Answer 25

We cannot use filtration to separate a solution. The solvent particles surround the solute particles. So, when we filter a sugar water solution, the sugar particles move through the filter paper with the water particles. The water particles and the sugar particles are small enough to pass through the filter paper. However, we can use evaporation to recover the solute particles from the solution. When the solution is heated, the particles on the surface of the liquid gain enough energy to escape into the atmosphere. If the process carries on long enough, all the liquid particles will change to gas particles. The solute particles will be left behind

Question 26

Define distillation.

Answer 26

Process of separating a solution by boiling so that the solvent evaporates, and then cooling the vapourised solvent so that it condenses

Question 27

Define condensation.

Answer 27

Change of state from a gas to a liquid; normally caused by cooling

Question 28

How and why would we use distillation?

Answer 28

If we want to collect both the solute and the solvent when we separate a solution, we can use distillation. Distillation involves evaporation followed by condensation.
Heat the solution so that the solvent evaporates. Instead of letting the solvent particles escape into the atmosphere, collect the vapour. Than cool the vapour so that it condenses to become a liquid again

Question 29

How else can we use distillation?

Answer 29

To separate a solution of two liquids. However, the liquids must have different boiling points.
Eg. A mixture of ethanol and water. Ethanol ia an alcohol with a boiling point of 78°C, which is lower than the boiling point of water. If you heat the solution to 78°C and keep the temperature there, only the ethanol will evaporate, leaving the water behind

Question 30

Define pigments.

Answer 30

Substances that give colour to living tissue, materials, paint and ink

Question 31

Define chromatography.

Answer 31

Method used to separate a mixture in which different parts of the mixture move through a medium at different speeds

Question 32

How can we use chromatography?

Answer 32

To separate a mixture of different pigments. Some pigments dissolve more easily than others. We can add a solvent such as water or alcohol to a mixture of pigments and let the solution travel through a medium such as paper. More soluble pigments will travel faster through the paper and cover a longer distance. Less soluble pigments will travel more slowly and only cover a short distance. In this way, we can identify the colours of the different pigments that were used to make the ink