water

Question 1

state the purpose of sedimentation

Answer 1

removes large particles

Question 2

state the process off filtration

Answer 2

removes smaller particles

Question 3

state the process of chlorination

Answer 3

kills bacteria

Question 4

what can desalination be carried out by and what’s its purpose

Answer 4

distillation and removes salt from sea water

Question 5

how can temporary hard water be softened

Answer 5

By boiling it

Question 6

How do you investigate hardness in water

Answer 6

Put a known volume of water into a boiling tube.
Add soap solution, one drop at a time, and shake the mixture for 10 seconds.
Record the number of drops of soap needed to make a lather. The greater the number of drops needed to make a stable lather, the harder the water.
To separate temporary and permanent hard water samples, boil the water.
Repeat steps two and three with the boiled samples.

Question 7

what does distillation do

Answer 7

Distillation can be used to separate and collect a liquid from a solution

Question 8

what is the process used to soften hard water

Answer 8

Distillation can be used to soften water as the water evaporates as it is heated and the ions are left behind

Question 9

what ion softens hard water

Answer 9

Sodium carbonate

Question 10

What does the layer of temporary boiling water form a layer of

Answer 10

Limescale

Question 11

why is rainwater naturally acidic

Answer 11

because it contains dissolved carbon dioxide from the air

Question 12

what is permanent hardness caused by

Answer 12

Permanent hardness is caused by dissolved calcium sulfate which does not decompose when heated

Question 13

give some advantages of hard water

Answer 13

some people prefer the flavour

calcium helps strengthens child’s teeth and bones

Question 14

give some disadvantages of hard water

Answer 14

difficult to form a lather with soap

limescale can form on appliances such as kettles and washing machines

Question 15

suggest a reason why energy may be wasted in homes in hard water areas

Answer 15

Hard water contains dissolved rock that accumulates on heating elements and the internal surfaces of boilers, causing scale build-up and impairing efficiency

Question 16

Which method can be used to remove temporary hardness but not permanent hardness from a sample of water?

Answer 16

Boiling water will remove temporary hardness but not permanent

Question 17

What ions cause hardness in water

Answer 17

Calcium and magnesium

Question 18

What dissolved compound is responsible for causing temporary hardness in water?

Answer 18

Calcium hydrogencarbonate causes temporary hardness in water

Question 19

Which statement correctly describes the method for determining the hardness of water?

Answer 19

Add soap solution to the water, shake until a lather is formed - the more soap added, the harder the water

Question 20

if a water sample has a volume of 7.0 before boiling and a volume of 2.5 after boiling what happened? And what type of water is it

Answer 20

Temporary hard water, as the volume of soap decreases a lot after boiling.

Question 21

What can be used to identify whether a sample of water is hard or soft?

Answer 21

Soap solution is added drop by drop and the water sample is shaken. The more drops it takes to get a stable lather (bubbles), the harder the water is.

Question 22

State why the temperature scale on a solubility graph ranges from 0°c to 100°c

Answer 22

as water is a liquid over this range. Each point along the curve represents a saturated solution at that temperature. Each point below the curve represents an unsaturated solution.

Question 23

Why is it important to quote solubility at a given temperature?

Answer 23

All major substances have solubilities affected by temperature, so it is important to quote the temperature at which the solubility measurements were taken

Question 24

What will happen to a hot saturated solution of copper(II) sulfate as the temperature decreases?

Answer 24

Crystals will form, As the temperature falls, so does the solubility.

Question 25

Why does the temperature scale on a solubility graph range from 0°C to 100°C?

Answer 25

Water solidifies at 0°C and boils at 100°C.

Question 26

What does desalination do

Answer 26

Removes salt from seawater

Question 27

Discuss why some people are against fluoridation of water supplies

Answer 27

Mass medication - takes away individuals choice

Discolouring teeth - fluorosis