Topic 3: Solutions are Special Mixtures

Question 1

When is a mixture a solution?

Answer 1

When one substance completely dissolves into another and you cannot see the different parts.

Question 2

A solution consists of two main elements. Name them.

Answer 2

A solvent and a solute.

Question 3

What is the difference between a solvent and a solute?

Answer 3

A solvent is the substance in which something is dissolved.
A solute is the substance that dissolves in the solvent.

Question 4

Name a very common solvent.

Answer 4

water

Question 5

What do you call substances that can dissolve in water?

Answer 5

Soluble substances

Question 6

What do you call substances that cannot dissolve in water?

Answer 6

Insoluble substances

Question 7

Can the substances in a solution be separated?
Why?

Answer 7

No, because the substances have completely dissolved into the solvent.

Question 8

Is sugar and sand a solution?
Give a reason for your answer.

Answer 8

No, sugar and sand is a mixture because you can still see the different particles.

Question 9

What does the rate of dissolving mean?

Answer 9

It is how quickly a substance dissolves in a liquid.

Question 10

James likes his coffee sweet with 3 spoons of sugar. He also adds milk.
Answer the following questions:
1.) Is the coffee in the cup a mixture? Give a reason for your answer.
2.) What would you call a cup of coffee then?
3.) Name the components in the cup of coffee.
4.) Which component is a solvent?
5.) Which component is a solute?
6.) What can James do to make the sugar dissolve quickly?

Answer 10

1. No, it is a solutions because you cannot see the different ingredients/components/particles anymore.
2. A solution
3. Boiling water, coffee, sugar, milk
4. Boiling water
5. Sugar
6. He can stir the coffee

Question 11

Name 3 ways in which a solute will generally dissolve faster.

Answer 11

If the solvent is hot.
If the solution is stirred or shaken.
If the grain size of the solute is small.

Question 12

What is the difference between melting and dissolving?

Answer 12

Melting is when a solid turns into a liquid due to heat.
Dissolving is when a solid mixes in a liquid and appears to disappear, but is still there.

Question 13

Crystallisation is when a substance from a liquid turns into small, hard crystals. Why does this happen?

Answer 13

This happens when a solute can no longer remain in the liquid/solvent.

Question 14

What are the 3 factors that affect solubility?
Write a sentence describing how they each affect solubility.

Answer 14

Temperature.
The hotter the solvent is, the faster the solute will dissolve.

Stirring
If the mixture is stirred or shaken, the solute will dissolve faster.
a
Grain size
If the grain size of the solute is small, it will dissolve faster.

Question 15

Explain the process of crystallisation.

Answer 15

If you leave a solution of salt and water in the sun, the sun will heat up the water.
The heat causes the water to evaporate.
The salt can no longer remain in the solution and separates from the solution and forms crystals.