2. water
• Water is a colourless,
odorless and
tasteless liquid.
• Water can exist in
three state:
- solid (ice)
- liquid (water)
- gas (steam)
3. The changes of water occur at specific temperature
Point Explanation Example
Melting The temperature which solid Meting point of ice
point becomes liquid = O oC
Freezing The temperature which liquid Freezing point of
point becomes solid water = 0 oC
Boiling The temperature which liquid Boiling point of
point becomes gas water = 100 oC
SOLID LIQUID GAS
melting boiling
freezing
4. Water test
The presence of water can be determined by the
tests shown below:
Water test Observation/Result
The freezing point The melting point of the water is 0 oC and
and melting point the boiling point of the water is 100 oC
(without any contamination)
Anhydrous cobalt Changes from blue to pink
chloride paper
Anhydrous copper(II) Changes from white to blue
sulphate
5. SOLUTIONS
A solution is a mixture formed when one or
more solutes dissolve in a solvent.
Water
(solvent) Sugar
solution
(solution)
Sugar
(solute)
6. Soluble and Insoluble
SOLUBLE INSOLUBLE
The substance will NOT
The substance will dissolve in a liquid and
dissolve in a liquid formed precipitate
7. When a solute dissolves
in solvent, the solvent
breaks down the solutes
into smaller particles
10. MASS OF A SOLUTION
Mass of a solution = Mass of the solvent + Mass of solute
When a solute dissolves in a solvent, it didn’t disappear!!
5 grams 20 grams 25 grams
SUGAR
WATER SOLUTION
11. solvents
Water is such a good solvent that it can dissolve almost
every solutes and it’s known as universal solvent.
A solution in which
the water is the
solvent is called
aqueous solution.
Example, salt solution
(salt + water)
12. However, some substances do not dissolve in the water.
Thus, organic solvents are used to dissolve it.
Some of the
examples are
alcohol, kerosene,
turpentine and
acetone.
13. solutions
Diluted solution Concentrated Saturated solution
solution
Excess
solute
Has very little Has a lot of solute Has the maximum
solute in it in it amount of solute in it
Can dissolve a lot Can dissolve a Cannot dissolve any
more solute little more solute more solute
15. CONCENTRATION OF A SOLUTION
• A concentration of a solution = grams per dm3 (g/dm3)
1 dm3 = 1000 cm3
Example 1,
Solution A contains 10.0g of solute in 1000cm3 solvent.
Concentration = mass of solutes (g)
volume of solvent (dm3)
= 10.0 g/1 dm3
= 10.0 g/dm3
16. Example 2,
Solution B contains 5.0g of solute in 1000cm3 solvent.
Concentration = mass of solutes (g)
volume of solvent (dm3)
= 5.0 g/1 dm3
= 5.0 g/dm3
17. Example 3,
Solution C contains 1.0g of solute in 100cm3 solvent.
Concentration = mass of solutes (g)
volume of solvent (dm3)
= 1.0 g/0.1 dm3
1000 cm3 = 1 dm3
= 10.0 g/dm3
100 cm3 = 0.1dm3
18. Example 4,
Solution D contains 10.0g of solute in 10 000cm3 solvent.
Concentration = mass of solutes (g)
volume of solvent (dm3)
= 10 g/10 dm3
1000 cm3 = 1 dm3
= 1.0 g/dm3
10 000 cm3 = 10dm3
19. Example 5,
Solution D contains 5.0g of solute in 100 cm3 solvent.
Concentration = mass of solutes (g)
volume of solvent (dm3)
= ?????
20. Example 6,
Solution E contains 0.1g of solute in 10 cm3 solvent.
Concentration = mass of solutes (g)
volume of solvent (dm3)
= ?????
21. Uses of solvents & solutions
(A) HOME Water is used for cooking, drinking, & cleaning.
22. Water is used to dissolve
detergents and many
types of stains
24. Mineral salts and fertilizers are
(B) AGRICULTURE
dissolved in water so that plants
can absorb them.
25. In hydroponics, the roots of plants are immersed in
solutions containing dissolved mineral salts.
26. (C) MEDICINE
Medicinal drugs are
sometimes mixed
with sugar solutions
to make them taste
better.
Examples are cough
mixtures and vitamin-
C enriched drinks
27. (D) INDUSTRY
Turpentine, alcohol
and other types of
solvents are used in
the manufacturing of
paints, inks and dyes.
28. SOLUBILITY
• A solvent can only dissolve a certain amount of
solute.
• Solubility is the maximum amount of solute in
grams that will dissolve in 100g of solvent.
• The solution produced is a saturated solution.
Solubility = ______ g of solute /100g of solvent
29. THE FACTORS AFFECTING THE SOLUBILITY
(1) The nature of
the solvent
(2) The nature of
the solute
(3) Temperature
30. (1) THE NATURE OF THE SOLVENT
• The solubility of a solute is different in different solvents.
• A polar (likes water) solute dissolved in polar solvent
(water).
• A non-polar (doesn’t like water) solute dissolved in non-
polar solvent (ether or alcohol)
Water Alcohol
(Polar solvent) (Non-polar solvent)
Salt (Polar
MORE SOLUBLE LESS SOLUBLE
solute)
Iodine (Non-
LESS SOLUBLE MORE SOLUBLE
polar solute)
31. Undissolved Dissolved iodine
iodine in water in alcohol
32. (2) THE NATURE OF THE SOLUTE
• Different solutes have different solubility in a given
solvent.
Solute Solubility at 20oC
(g/100mL of water)
Copper (II) sulphate 20
Potassium nitrate 30
Sodium chloride 38
***Among the 3 solutes, sodium chloride
is the most soluble in water.
33. (3) THE TEMPERATURE
• Generally in many
cases solubility
increases with the
rise in temperature
• Decreases with the fall
of temperature but it
is not necessary in all
cases.
• Gases are more
soluble in cold solvent
than in hot solvent.
35. acid
• The word comes from Latin word ‘acidus’, which
means sour.
• Acid in food gives the food a sour and tangy
taste.
• Acids in the laboratory are harmful. Example:
– Hydrochloric acid
– Sulphuric acid
– Nitric acid
39. (d) Dilute acids react with reactive metals
to form hydrogen gas.
Dilute + zinc
hydrochloric
Bubbles of acid
hydrogen
gas
zinc + hydrogen
chloride
40. To identify the gas
produced: use a
lighted splint.
Hydrogen gas
extinguished a
lighted splint with a
“pop” sound.
41. (e) Dilute acids react with carbonates to
produce carbon dioxide
Dilute nitric + calcium
acid carbonate
calcium + water + carbon
nitrate dioxide
42. Diluted acid +
carbonate To identify the gas
produced: pass it
through some lime
water (calcium
hydroxide solution)
A white precipitate is
formed when carbon
dioxide gas is bubbled
into limewater.
Limewater
43. alkali
• Alkali is the chemical ‘opposite’ of acid
• Alkali are often used in many household
cleaners such as detergents, soap and etc
• Alkalis that are commonly used in the
laboratory are:
– Ammonia solution
– Sodium hydroxide
– Potassium hydroxide
44. Properties of alkali
(a) Alkalis have bitter taste and are
soapy and slippery when touch
45. (b) Strong alkalis are corrosive.
Strong alkali like sodium hydroxide are highly corrosive
47. indicators
An indicator is a dye or a mixture of dyes which changes
color according to the acidity or alkalinity of a substance.
48. Litmus paper
The main use is to test whether the solution is
acidic or alkaline.
Test with acid Test with alkali
Red litmus paper No changes Red blue
Blue litmus paper Blue red No changes
49. pH scale
The pH scale is used to express acidity and alkalinity.
Acidic Neutral Alkali
50. How to check the pH of the solution?
Two ways
Universal Universal
indicator paper indicator solution
54. ALKALI
To neutralize an acid,
an alkali is used.
The alkali is dripped
into a conical flask
containing acid and
stop once the color
changes from red
(acidic pH) to green
(neutral pH).
ACID
55. ACID
To neutralize an alkali,
an acid is used.
The acid is dripped
into a conical flask
containing alkali and
stop once the color
changes from dark
blue (alkalic pH) to
green (neutral pH).
ALKALI
56. USAGE OF NEUTRALIZATION
An alkali, magnesium hydroxide is used in the toothpaste to
neutralize the acids produced by the bacteria in the mouth
57. Farmers add slaked lime (calcium hydroxide) to
neutralize excess acid in the soil
58. A mild alkali such as sodium hydrogen carbonate is
used to treat a bee sting which is acidic.
