Solutions and suspensions

Question 1

What happens when you mix salt in water and stir it?

Answer 1

When stirred, the salt mixes completely
with the water and cannot be seen.
We say that
• salt dissolves in water
• salt is soluble in water

Question 2

What are solutions?

Answer 2

Solutions are mixtures in
which soluble particles are
completely dissolved
in a liquid or gas.

When salt is mixed with water, the solid salt dissolves
into the water, forming a solution.

Question 3

What is solute, solvent, and solution?

Answer 3

A solute (e.g. salt) is the substance that dissolves in
a solvent.
• A solvent (e.g. water) is the substance that
dissolves the solute.
• The solution (e.g. saltwater) is the mixture of the
solute and the solvent.

Question 4

How do we create a solution?

Answer 4

Solute + Solvent = Solution

Salt + Water = Salt solution

Question 5

What is soap water solution used for?

Answer 5

Soap + Water = Soap water solution

Everyday use:
Washing clothes

Question 6

What is sugar syrup used for?

Answer 6

Sugar + Water = Sugar syrup

Everyday use:
Sweetening
tea and coffee

Question 7

What are some solutions around us?

Answer 7

Carbonated drinks
Carbon dioxide is dissolved
in sugar solution to make
carbonated drinks.

Dyes
Dyes are dissolved in
water to produce colourful
fabric dyes.

Syrup
Syrup is dissolved in
water to make drinks.

Question 8

What are amalgams?

Answer 8

•When you get a tooth cavity,
dentists would usually seal it
with a filling.
•This would prevent bacteria
from easily entering the open
spaces and causing further
decay.
•Dental fillings are actually
amalgams – a type of solution
– which formed when mercury
dissolves another metal (eg
silver).

Question 9

What are suspensions?

Answer 9

Suspensions are mixtures
in which insoluble particles
are suspended in
a liquid or gas.

Question 10

How do we create a suspension?

Answer 10

Insoluble
substance

+ Liquid = Suspension

Sand + Water = Sandy water
suspension

Question 11

What are some suspensions that are around us?

Answer 11

• Here are some common examples of
suspensions:

antibiotics ,orange juice ,drain water

Question 12

How do you separate an insoluble solid?

Answer 12

It is easy to separate
an insoluble solid by
filtering the mixture.

The insoluble solid cannot
pass through the filter paper
but the water can.

The sand that is trapped by the filter
paper is called the residue. The water
that passes through the filter paper is
called the filtrate.

Question 13

What are the properties of solutions and suspensions?

Answer 13

Properties of Solutions Properties of Suspensions

• Homogeneous Not homogeneous
• Residue present after
filtration
• Separation of substances
when left to stand
• No residue after
filtration
• No separation of
solute and solvent
when left to stand•

Question 14

What is solubility?

Answer 14

• There is a limit to the amount of solute that can
dissolve in a given amount of solvent at a given
temperature.
• This limit depends on the solubility of the
solute.

• Solubility is the ability of a solute to dissolve in
a solvent.
Definition of Solubility

Solubility is the
maximum amount
of solute that can
dissolve in 100g of
solvent at a given
temperature.

Question 15

What are the factors that affect solubility?

Answer 15

• The nature of the solvent
• The nature of the solute
• Temperature

Question 16

How does temperature affect solubility?

Answer 16

Does sugar dissolve in cold tea?
It does, but not as much as in a
cup of hot tea.

The sugar is more soluble at
higher temperatures.

• The solubility of a substance usually
increases as the temperature increases.

• Gases are unusual because their solubility
decreases when the solvent gets hotter.

Question 17

What are saturated solutions?

Answer 17

A saturated solution is a solution that
contains the maximum amount of solute
dissolved in it at that temperature.

On cooling a saturated solution, crystals
will form.

Question 18

WHat is the rate of dissolving?

Answer 18

The rate of dissolving is
how fast a substance
dissolves in a fixed
volume of solvent.

Question 19

What are the factors that affect rate of dissolving?

Answer 19

• Temperature
• Rate of stirring

• Size of solute particles

Question 20

Elaborate further on the factors that affect the rate of dissolving

Answer 20

Temperature
The higher the temperature of the
solvent, the faster we can expect the
solute to dissolve.

Rate of stirring
The faster the rate at which we stir
the mixture, the faster we can expect
the solute to dissolve.
Size of solute particles
The smaller the solute particles, the
faster we can expect the solute to
dissolve. Small particles have a larger
surface area that comes into contact
with the solvent.

Rate of stirring
The faster the rate at which we stir
the mixture, the faster we can expect
the solute to dissolve.