GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME
PHYSICAL SCIENCES
GRADE 10
SESSION 20
(LEARNER NOTES)
THE DISSOLUTION PROCESS
Learner Note: Most chemical reactions happen in a watery solution. Not all substances are
soluble. It is important to be able to determine what will happen when a substance is added to
water – dissolve, dissociate, conduct electricity or it may be insoluble.
SECTION A: TYPICAL EXAM QUESTIONS
Question 1: 30 minutes
Learner Note: Terminology in this section is easy to understand but make sure that it is
practised.
During an investigation distilled water is used as a solvent for a number of solutes to
determine the relationship between the conductivity and nature of the dissolved substance.
(Dissolve sugar, table salt, hydrochloric acid, ammonia, alcohol). 100 mℓ water is placed into
a beaker. A circuit is set up as shown below. This is used to determine the conductivity of the
solution.
1.1
What is a solute?
(Solutes are not always solids, refer to definition)
(2)
1.2
What is a solvent?
(2)
Learner Note: Understand that solutions are not always in the watery phase (aq), air is a gas
solution, brass is a solid solution. Identify the solute and solvent in different examples.
1.3
Give three constant variables in the investigation, state how each of these can affect
the investigation.
(9)
(Use full sentences and state exactly what must be kept constant, many marks
are lost due to vague answers)
1.4
1.5
1.6
What is the independent variable?
(1)
What is the dependant variable?
(1)
Write an investigative question for the investigation
(2)
(Start with .... What is the relationship between..., remember the question mark!)
1.7
Explain why it is important to use distilled water in the investigation
(2)
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GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME
PHYSICAL SCIENCES
GRADE 10
SESSION 20
(LEARNER NOTES)
Learner Note: Gases dissolve or react in water. This is of importance in the acid rain
explanations. Understand well. Solubility of gases relates to the polarity and nature of water
and the gas.
1.8
1.9
When a container of distilled water is opened and left for a while, it cannot be used as
distilled water any more. Explain.
(3)
Predict the conductivity of each of the solutions. Give reasons for your answers (15)
(First determine what particles the substance is made up of, this will give you an
indication of the conductivity, ions cause electrolytic solutions)
(37)
SECTION B: SOLUTIONS AND HINTS
Question 1:
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
The substance that is dissolved to produce a solution 
The substance which dissolves a solute to form a solution. If water is used, it is the
solvent.  The substance that has the greatest proportion is the solvent ie. In air all
gasses are dissolved in nitrogen which is the solvent as it is present in the greatest
proportion.
The volume of water must be the same, the concentration of the solution depends on
the volume of water used.  Less water, greater concentration and the greater the
conductivity.
The amount of solute must be the same,  it affects the concentration  and therefore
the conductivity of the solution 
The temperature of the water must be the same,  most dissolution processes are
endothermic and therefore increases when the temperature is increased. If more
solute is dissolved, the conductivity may increase 
(Answer in detail, use appropriate terminology, state increase or decrease etc.
Vague answers will not be awarded marks.)
The type or nature of solute dissolved in the water 
The conductivity of the solution 
What is the relationship between the nature or type of solute and the conductivity of the
solution if dissolved in distilled water of the same volume and temperature 
Distilled water is pure,  contains no dissolved substances that might increase the
conductivity or cause a precipitate to form when the solute is added. 
Gases in the air dissolve in the water and ions are formed. The water is now a
solution and no longer pure 
Sugar – not conducting , molecules in solution
Table salt – conducting , ions form in solution 
Hydrochloric acid – conducting , ions in solution 
Ammonia – conducting , ions in solution 
Alcohol – not conducting , molecules in solution 
(Make sure you understand bonding to predict the nature and type of the
particles in a solute.)
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GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME
PHYSICAL SCIENCES
GRADE 10
SESSION 20
(LEARNER NOTES)
SECTION C: ADDITIONAL CONTENT NOTES
Water is a polar molecule. It has polar bonds between the hydrogen and oxygen and the
molecule is asymmetrical. The one end is slightly negative (O – end), the other is slightly
positive. Water molecules attract each other with strong hydrogen bonds.
It is a very good solvent and dissolves other polar substances and ionic substances. Ionic
substances are polar as they are made up of oppositely charged ions. Charged ions give rise
to the polar nature. The ions are attracted by strong electrostatic forces in the crystal lattice.
These forces hold the ions together in the crystal. When an ionic substance is placed in water
and the intermolecular forces are similar, the ions dissociate in the water – they move away
from each other. This solution contains the ions, ions can conduct electricity in a solution –
the more ions it contains the more electricity it conducts. This solution is called an electrolyte.
Alkalis dissolve in a similar way in water. When the ions are dissociated, they are surrounded
by water molecules – this prevents them from reforming into a crystal structure. When the
water evaporates, the ions can form an ionic substance again. Electrolysis can be used to
separate chemical elements in a solution.
Covalently bonded molecules eg. Acids are made up of atoms that share electrons during
bonding. They are not made up of ions and can therefore not dissociate into ions. These
substances ionise when they dissolve in water.
Gases can dissolve to form ionic solutions. This causes acid rain.
The SSIP is supported by
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GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME
PHYSICAL SCIENCES
GRADE 10
SESSION 20
(LEARNER NOTES)
SECTION D: HOMEWORK
Learner Note: As you attempt the homework, you need to ensure that you are able to
answer the questions in the allocated time frames. If you get stuck, you should refer to either
the additional notes or your class teacher.
Question 1: 40 minutes
Complete the following table
SUBSTANCE
FORMULA
PARTICLES
FORMED IN
SOLUTION
VERY SOLUBLE,
SLIGHTLY SOLUBLE
OR INSOLUBLE
GOOD
CONDUCTOR,
POOR
CONDUCTOR,
NON
CONDUCTING
Sodium
hydroxide
sodium carbonate
silver chloride
calcium nitrate
barium sulphate
glucose
copper(ii)
sulphate
ethanol
carbonic acid
acetic acid
hydrochloric acid
(44)
The SSIP is supported by
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GAUTENG DEPARTMENT OF EDUCATION SENIOR SECONDARY INTERVENTION PROGRAMME
PHYSICAL SCIENCES
GRADE 10
SESSION 20
(LEARNER NOTES)
SECTION E: SOLUTIONS TO SESSION 19 HOMEWORK
Question 1:
1.1
Informal settlements  ; agriculture ; wetlands destruction ; commercial forestry ;
littering , oil , chemicals and medicine ; industry 
1.2
Cholera ; typhoid ; gastroenteritis , bilharzias ; shigella dysentery.
1.3



Bathroom:
Check taps and toilets for leaks or drips.
Take short showers or shallow baths.
Flush toilets with bathwater etc.



Kitchen and laundry:
Use only full loads in washing machines and dishwashers.
Use plug to wash dishes not running water.
Use a glass to drink water, not a running tap.


Outside home:
Wash car with buckets of water not a running hose.Close taps in public places.
Sweep the driveway don’t wash it.
(Any 4 clearly explained!, one mark each )
1.4
1.
2.
3.
4.
5.
6.
A 
C 
D 
C 
B 
D 
The SSIP is supported by
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