TYPES OF MIXTURES
NOTES:

Mixtures are made up of two or more pure substances mixed together. The three different
types of mixtures we will discuss are solutions, suspensions and colloids.

The difference in these mixtures is in the size of the particles. Solutions have the smallest
particles which cannot be seen with the naked eye, followed by the particles in a colloid
mixture. The particles in a suspension are the largest and are visible to the naked eye.
These particles will also settle out of the mixture after a period of time.
QUESTIONS:
1. In your own words, explain the difference between a pure substance and a mixture.
A pure substance is the substance. A mixture is 2 pure substances mixed together
2. List two examples of pure substances and two examples of a mixture.
Sand and water and mixtures are solutions and colloids
3. Fill the gaps: A colloid contains smaller particles than a suspension , but bigger particles than
a solution, and will settle out of a liquid if left long enough.
SOLUTIONS
NOTES:

A solution is a mixture of a solute (the substance being dissolved) and a solvent (the
substance doing the dissolving).

It is important to note that solutions are transparent (can look through them), even when
they are coloured you can still see through them.

The more solute that is added to a solvent the higher the concentration of the solution will
be. If a solution has a large amount of solute it is referred to as a concentrated solution. A
dilute solution has a small amount of solute dissolved in the solvent.

A saturated solution is one that is so concentrated that no more solute will dissolve.
QUESTIONS:
4. When salt and water are mixed, they make salt water. Is this a new substance? Explain your
answer.
No because they are just two particles getting mixed. They are still water and salt
5. When instant coffee is mixed with hot water, identify the:
a) Solute - coffee
b) Solvent - water
c) Solution - both
6. In your own words, explain the difference between dissolving and melting.
7. When a substance dissolves in water it seems to disappear. Explain where it goes.
SUSPENSIONS
NOTES:

In a suspension the particles are much bigger than the particles of the solvent and therefore
they will not dissolve. Substances that will not dissolve are known as insoluble. Substances
that will dissolve are known as soluble.

Solubility is a measure of the amount of substance that will dissolve in a solvent. The more
substance that is dissolved the higher the solubility.

When left for long enough the particles in a suspension will sink to the bottom of the
mixture. The solid particles that sink to the bottom form a layer called sediment.
QUESTIONS:
8. How could you test if cordial is a suspension or a solution?
9. What do you call the substance that settles out of a suspension?
10. Why is it important that some medicines are shaken before being taken?
COLLOIDS
NOTES:

As you know particles in a colloid are bigger than a solution but smaller than a suspension.
The particles are not big enough to settle out of the solvent. They are big enough to reflect
light, so less light will pass through colloids. This means, unlike a solution, colloids are not
transparent (they are not see through, but cloudy).

There are many different types of colloids due to the fact that all solids, liquids and gases
can form this type of mixture. These colloids are:
-
A sol is a colloid that has solid particles spread throughout a liquid.
-
An emulsion is a colloid that has liquid particles spread throughout another liquid.
-
Foam is a colloid that has gas particles spread through a liquid.
-
A gel is a colloid that has liquid particles spread throughout a solid.
-
Smoke is a colloid that has solid particles spread throughout gas.
-
Mist is a colloid that has liquid particles spread throughout gas.
QUESTIONS:
11. How could a torch show if you have a colloid or a solution?
12. Is steam from a kettle a colloid? Explain your answer.
13. Give an example of a colloid that is:
a) a solid in a liquid b) a liquid in a gas c) a liquid in a liquid -
EMULSIONS
NOTES:

Emulsions are a special type of colloid where liquid particles are spread another liquid.

Normally oil and water don’t mix (two liquids) but when you add an emulsifier the liquid
being mixed will break into tiny droplets.

Emulsions that require an emulsifier can be either an oil-in-water (oil droplets in large
amount of water) or water-in-oil (water droplets in a large amount of oil) emulsion.
QUESTIONS:
14. (a) Give an example of a household emulsion
that this diagram could describe.
(b) This mixture is not a solution, but suggest
one way in which it is similar to a solution.
15. Describe how detergent changes an oil and water suspension into an emulsion.
16. Bile, which helps us digest fats, mixes with the partly digested food in your small intestine. It
is an emulsifier. How do you think it assists us in breaking down foods?
SEPARATING SOLIDS FROM MIXTURES
NOTES:

Sometimes we need to separate mixtures to obtain pure substances. We can do that by
using the following techniques:
-
Decanting is used when separating suspensions. You allow the solid to settle at the
bottom and then slowly pour the liquid off the top. Used when your separation needs
to quick, not perfect.
-
Sieving is used when one particle is larger than the other. Smaller particles will pass
through the holes whereas the larger particles will be left in the container.
-
Filtration is used instead of decanting when complete separation is necessary. It uses a
filter to allow the liquid (filtrate) to pass through and traps the solid (residue) in the
filter.
-
Gravity Separation is used when you have particles of different weight. When you stir
or shake these particles the heavier one will tend to move to the bottom of the
container.
-
Centrifuging is a type of gravity separation where a mixture is spun around quickly.
While it is spinning the heavier particle will move to the bottom and the lighter particle
will move to the top.
-
Magnetic Separation is used when an object in a mixture has magnetic properties. You
use a magnet to separate the particles.
QUESTIONS:
17. When is decanting used as a method of separation?
18. Explain the main difference between sieving and filtration?
19. Where do the heavy particles in a mixture end up because of gravity?
20. A quarry produces a mixture of small and large crushed rock pieces. What simple method
may be used to separate the small and large pieces?
21. The diagram below shows equipment set up for a filtration experiment. What are the letters
in the diagram representing?
ABC-
SEPARATING SOLUBLE SUBSTANCES FROM MIXTURES
NOTES:

Soluble substances cannot be separated through filtration because the particles of the
solute are too small. Therefore we must use the following techniques to separate solutions:
-
Evaporation is when you heat the solution so the solvent evaporates, which will leave
the solute in the container as a residue of crystals.
-
Distillation is the same as evaporation but the gas (distillate) is collected and cooled to
create distilled water.
-
Chromatography is a technique that is used to separate mixtures due to their solubility.
A spot of the mixture is placed on filter paper and placed in water. The substances in
the mixture with higher solubilities will move further up the filter paper.
QUESTIONS:
22. Salt water is evaporated. What is left behind as crystals and what is “lost”?
23. Explain the difference between distillation and evaporation?
24. What is chromatography used to separate?
25. Distillation is used to make brandy from wine. As the wine mixture is heated gently and the
alcohol and wine evaporates and are condensed, some of the water is removed. Does the
wine have a higher or lower concentration of alcohol than brandy?