Notes

CHAPTER 5: WATER AND SOLUTIONS
5.1 PHYSICAL PROPERTIES OF WATER
1. Water is a colourless, odourless and tasteless liquid.
2. Water exists in three states, which are solid (ice), liquid
(water) and gas (steam).
3. Water can change from one state to another.
Melting boiling/evaporation
Ice water gas/steam
Freezing condensation
4. The changes in the state of water occur at specific
temperature.
5. The temperature of a substances remains constant, that
is it does not rise or drop, during the change of state.
6. The density of water is 1 g per cm3
. 1 cm3
of water has a
mass of 1 gram. For example, 50 cm3
of water has a
mass of 50 g.
7. Water is a poor conductor of heat.
Draw figure 5.1 page 3 text book volume 2
The relationship between the freezing and boiling points of
water and the Kinetic Theory
1. When water is cooled, the particles lose kinetic energy
(heat is released). The particles move more slowly. Science Form 2 note Teacher zaidi@maher2010
2. At freezing point, liquid particles cannot move freely
anymore.
3. Liquid particles are pulled together by strong forces of
attraction between particles.
4. This is why solid particles cannot move freely. A liquid
changes into a solid at freezing point.
Draw figure 5.3 page 4 text book volume 2
5. When heat energy is supplied to a liquid, the liquid
particles obtain a lot of kinetic energy and they vibrate
faster.
6. At boiling point, the energy obtained enables the liquid
particles to overcome and break the forces of attraction
between the particles.
7. Boiling is the physical process in which water changes
into steam.
8. Liquid particles are feed and change into gas at boiling
point.
Draw figure 5.5 page 5 text book volume 2
5.2 WATER COMPOSITION
http://peer.tamu.edu/curriculum_modules/water_quality/mod
ule_4/lesson.htm
The electrolysis of water
1. Water is a chemical compound that consists of two parts
hydrogen and one part oxygen.
+ =
2 hydrogen atoms 1 oxygen atom 1 water moleculeScience Form 2 note Teacher zaidi@maher2010
2. The ratio of hydrogen to oxygen in one molecule of
water is 2:1.
3. Water can be separated into hydrogen and oxygen
through the process of electrolysis. Hand out ms216 new vision – east
view
Draw figure 5.9 page 7 text book volume 2
*name the gas that is discharged at the anode. Oxy – required for burning
Name the gas that is discharged at the cathode. Hyd – pop sound
5.3 THE PROCESS OF WATER EVAPORATION
Water evaporation
1. Water evaporation is a process in which liquid is slowly
lost from surface of the liquid in the form of water vapour
into atmosphere.
2. Evaporation occurs at any temperature and at any time.
3. When water evaporates, its changes into gas called water
vapour.
4. The amount of water vapour in the air is called its
humidity.
5. The rate of water evaporation is influenced by a few
factors and can be explained using the Kinetic Theory .
6. The factors that affect the rate of evaporation of water
are:
a. surface area
b. temperature
c. humidity
d. air movement
buat eksperimen spt m/s 9-11
Draw figure 5.15 page 12 text book volume 2 Science Form 2 note Teacher zaidi@maher2010
Evaporation and boiling
and
Water gas
1. Evaporation takes place at any temperature and at any
time.
2. Evaporation occurs only at the surface of the water and is
a slow process.
3. Boiling only takes place at boiling point 1000C and all
throughout the water.
4. Boiling is a quick process.
Draw photograph 5.2 page 12 text book volume 2
Science info:
Test for presence of water.
a. anhydrous copper sulphate changes colour from white to blue.
b. Cobalt chloride paper changes colour from blue to pink.
5.4 SOLUTIONS AND SOLUBALITY OF SUBSTANCES
Solvent, solute and solution
1. A solvent is a liquid that is used to dissolve a substance
(solute).
2. A solute is the substance that dissolves in a solvent.
3. A solution is the mixture that is formed a solvent and a
solute (solutes dissolved in a solvent). Science Form 2 note Teacher zaidi@maher2010
Draw figure 5.16 page 13 text book volume 2
Dilute solutions, concentrated solutions and saturated
solutions
1. A dilute solution is a solution that has very little solute.
2. A concentrated solution is a solution that has a lot of
solute.
3. A saturated solution is a solution that has the maximum
amount of solute. A saturated solution cannot dissolve
any additional solute that is added to it.
Draw figure 5.17 page 14 text book volume 2
Suspensions
Go to www.chemtutor.com/solution.htm to gain information on the nature of
solutions, concentration of solutions and solubility. For easy access, go to
www.icd.com.my
1. A suspension is a liquid that has small particles in it. The
small particles are known as suspended substances.
2. The suspended substances do not dissolve in water.
3. When left aside, the suspended substances will sink to
the base of the container and the solution formed is clear.
Draw/Photostat table 5.3 page 16 text book volume 2
The solubility of solutes (eksperimen spt m/s 17-19)
1. The solubility is the maximum amount of a solute which
can dissolve in a given amount of solvent at a fixed
temperature.
2. The solubility of a solute is the quantity of dissolved
solute (in grams) in 100 ml of water at a specific
temperature, to form a saturated solution. Science Form 2 note Teacher zaidi@maher2010
3. For example, the solubility of calcium chloride in water is
120g per 100 ml of water at 400C. This means that 120g
of calcium chloride salt dissolves in 100 ml of water at a
temperature of 400C to form a saturated solution of
calcium chloride.
4. The solubility of different solutes in the same volume of
solvent, but at different temperatures is different, as
shown in Figure 5.13. The graph shows that:
(a) The solubility of potassium nitrate increases
the most quickly when the temperature
increases.
(b) The solubility of sodium chloride does not
change very much as the temperature
increases.
(c) At 2000C, the potassium nitrate, potassium
chloride and sodium chloride have the same
solubilities.
(d) At 0
700 C , calcium chloride and potassium
nitrate have the same solubility.
(e) The solute of different salts has different
solubilities.
(f) Solubility increases as the temperature
increases.
5. The difference in the solubility rates of solutes at specific
temperatures.
6. A few factors affecting solubility of a solute are:
a. The nature of the solvent.
i. the solubility of a solute depends on the
nature of the solvent.
ii. Example; soluble in water, less soluble in
ethanol and not soluble in diethyl ether.
b. The nature of the solute.
i. the solubility of a solute depends on the
nature of the solute.
ii. Example, sugar more soluble than salt.
c. The temperature.Science Form 2 note Teacher zaidi@maher2010
i. decrease in temperature decrease the
solubility of solids in liquid.
ii. increase in temperature increase the
solubility of solids in liquid.
iii. increase in temperature decrease the
solubility of gases.
The importance of water as an universal solvent
1. Water is called the universal solvent.
2. This is because a large variety of substances can dissolve
in it.
3. Water, as an universal solvent;
a.
b.
c.
d. salin dari textbook m/s 20
e.
f.
g.
4. Substances that do not dissolve in water may be soluble
in organic solution such as alcohol, thinner, turpentine,
petrol, kerosene.
5. Application of organic solvent in daily life. Science Form 2 note Teacher zaidi@maher2010
5.5 ACIDS AND ALKALIS
1. A solution in which water is known as an aqueous
solution.
2. Two common types of aqueous solution that we use
everyday are acid and alkalis.
Acids
1. An acid is a chemical substance that has a
hydrogen atom, which can be replaced by a metal
or ammonium.
2. Acids can be divided into two groups – organic
acids and inorganic acids (mineral acids). Lihat
power point
3. Acids exist in three states which are:
a. solid – for examples, tartaric acid
b. liquid – for examples, ethanoic acid (acetic
acid)
Organic solvent
-Alcohol used in the preparation of antiseptics
when dissolved in iodine
Turpentine is used in the preparation
of dilute paints.
Petrol is used in the preparation of perfumes.
Ether is used in the extraction of fats and oils.
Amyl acetate is used in the preparation
of cosmetic products such as lipsticks.
Acetone is used in the preparation cosmetic
products such as varnish and lipsticks.Science Form 2 note Teacher zaidi@maher2010
c. gas – for examples, hydrogen chloride
The Properties of Acids
http://education.yahoo.com/reference/dictionary/entry/acid
1. Acids have the following properties:
a. Taste sour
b. Are corrosive
c. Change blue litmus paper to red
d. Have pH values of less than 7
e. React with carbonates to release carbon dioxide
and form salt and water.
Acid + carbonate salt + water + carbon dioxide
f. React with active metals (magnesium/
aluminium/zinc/lead) to release hydrogen and
form salts.
Acid + metal salt + hydrogen
g. Reacts with alkalis to form salt and water
(neutralisation process)
Acid + alkalis salt + water
ACIDS USES
formic acid Coagulates latex (rubber tree)
acetic acid (vinegar) 1.preserve food like pickles
2.used in food
sulphuric acid
1.used in car battery
2.to make detergent and
fertilizer
tartaric acid to make soft drink
nitric acid to make chemical substances Science Form 2 note Teacher zaidi@maher2010
such as fertilizer, plastic and
explosives.
hydrochloric acid to make disinfectants and
liquid washing agents
citric acid used in fruit juices
Alkalis
1. An alkali is a hydroxide or metal oxide that
dissolves in water.
2. An example of alkalis are potassium hydroxide,
sodium hydroxide, calcium hydroxide (lime
water), and ammonium hydroxide (ammonia
solution) solutions.
The properties of Alkalis
http://education.yahoo.com/reference/dictionary/entry/alkalis
Alkalis have the following properties:
1. taste bitter
2. feel slippery like soap when touched with the fingers
3. are corrosive
4. change red litmus paper to blue
5. have pH values of more than 7
6. react with ammonium salts to release ammonia when
heated.
7. react with acids to form salt and water (neutralisation
process)
alkalis uses
Sodium to make soap
slaked lime, camphor (calcium
hydroxide)
1.neutralises acidic soil
2.to make cement
ammonium solutions
(ammonium hydroxide)
1.prevent latex from coagulating
2.to make fertilizer
pH Values (punier Hydrogen) Science Form 2 note Teacher zaidi@maher2010
1. The pH value of substances shows if the substance is
acidic, neutral or alkaline.
2. he pH scale has values from 1 to 14.
a. Acidic conditions (pH 1 – 6): substances with a
value of pH 1 is far more acidic than a substance
with a values of 6.
b. Neutral condition (pH 7) : neither acidic nor alkaline
c. Alkaline conditions (pH 8 – 14): a substance with a
pH value of 14 is far more alkaline than a substance
with a pH value of 8.
3. The pH values of substances are determined by using
pH paper or universal indicator solutions.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Acidity increases neutral alkalinity increases
Neutralisation
1. Neutralisation is the reaction that occurs between an
acid and an alkali to form salt and water.
Acid + alkali salt + water
2. At the neutralisation point, all the acid completely reacts
with the alkali. The solution formed does not show acidic
or alkaline properties and has a pH value of 7.
3. The salt formed from the neutralisation process depends
on the type of acid and alkali used, as shown in the
following table.
4. The method of mixing alkali and acid using a burette to
achieve the point of neutralisation is known as the
titration method.
Acid alkali salt water Science Form 2 note Teacher zaidi@maher2010
hydrochloric
acid
sodium
hydroxide
sodium
chloride water
sulphuric
acid
calcium
hydroxide
calcium
sulphate water
nitric acid calcium
hydroxide
calcium
nitrate water
hydrochloric
acid
ammonium
hydroxide
ammonium
chloride water
5.6 METHODS OF PURIFYING WATER (PMR 2008)
Filtration (PMR 2008)
1. Filtration makes use of a filter through which liquids
such as water and solutions pass through while insoluble
solids do not.
2. The liquid that pass through the filter is called the filtrate.
3. The solid that is left on the filter is called the residue.
Draw figure 5.36 page 28 text book volume 2
Distillation (PMR 2008)
Http://www.apswater.com/page43.html
1. When mixture of water and impurities is heated until it boils,
only the water changes into steam while its impurities are
left behind.
2. The steam is then cooled and condensed to produce pure
water.
Draw figure 5.37 page 29 text book volume 2
Sedimentation
1. A mixture of water and heavy insoluble solids will separate
after a while. Science Form 2 note Teacher zaidi@maher2010
2. The solids will settle or sink to the bottom as sediments
due to gravity.
Boiling (PMR 2008)
1. Boiling water kill most, if not all, micro-organisms present
in the water.
2. All drinking water must be boiled.
3. Some of the bacteria may be harmful. (diarrhoea and
cholera)
Chlorination (PMR 2008)
Go to www.dcs.ex.ac.uk/water to gather information about water and how it is
treated. For easy access, go to www.icd.com.my
1. Chlorination is a gas which an kill micro-organisms.
2. When chlorine is added into water, most micro-organisms
are killed and the dissolved gas will leave the water after
some time.
Ozone
1. Ozone is another gas that can kill micro-organisms in
water.
2.. It is now used in swimming pools to replace chlorine, as it
does not have a strong smell or bleaching effect like
chlorine.
Ultraviolet Light
Ultraviolet Light can kill micro-organisms in water.Science Form 2 note Teacher zaidi@maher2010
It is now used to sterilise the water in fish ponds and the food
processing industries.
5.7 WATER SUPPLY SYSTEM (PMR 2008)
1. The main source of water in our country is rainwater and
river water.
2. Before it is purified, rainwater and river water is collected
in reservoirs/dam. The water is then pumped to water
purification plants to be purified.
3. The following are the different stages of water
purification at the waterworks.
Draw figure 5.38 page 31 text book volume 2 (PMR 2008)
Salin stage 1, stage 2, stage 3, stage 4, stage 5 dari textbook
ms 31-32
Water purification and supply system
1. In some places, fluoride is added to reduce tooth decay.
Step to save water,
a. bathe by showering
b. Wash clothes in big quantities.
c. Wash vegetables in a basin.
d. Repair all water pipe leaks immediately.
e. Turn off the tap when not in use.
f. Use a watering can to water plants.
5.8 PRESERVING WATER QUALITY
Water pollution occurs when water is dirtied by waste thrown
into it. Polluted water is no longer suitable for living things. Science Form 2 note Teacher zaidi@maher2010
Water pollutants
http://en.wikipedia.org/wiki/water_pollution
http://www.ec.gc.ca/water/en/manage/poll/e_poll.htm
1. There are various water pollutants:
a. Domestic waste such as rubbish, animal carcasses and
faeces.
b. Industrial waste such as chemical residual (acid and
alkaline solutions) and radioactive substances.
c. Chemical substances in agriculture such as pesticides,
chemical fertilisers and agriculture waste (latex and oil
palm)
d. Mud and silt caused by the construction industries and
logging.
Draw figure 5.4 page 33-34 text book volume 2
The effect of water pollution on living things.
1. Water pollution brings about adverse effects on the
equilibrium in nature.
2. the effects of water pollution on living things include:
a. polluted water cannot be used for drinking or
bathing. Polluted water causes diseases such as skin
diseases and cholera.
b. Aquatic like such as fish, prawn will die. This reduces
the fisherman’s catch and the human food supply.
c. Aquatic life that are poisoned by chemicals such as
lead or mercury will cause adverse effects if eaten.
Dictionary
Aqueous solution – larutan berair Science Form 2 note Teacher zaidi@maher2010
Boiling – pendidihan
Bonds - terikat
Coagulate – menggumpal
Colourless - tidak berwarna
Compound – sebatian
Concentrated solution – larutan pekat
Condenses – memeluap
Dilute solution – larutan cair
Discharge – terhasil
Distillation – penyulingan
Filtration – penurasan
Humidity - kelembapan
Impurity – bendasing
Marine product – hasil laut
Melting point – takat lebur
Metal oxide - oksida logam
Mud and silt - Lumpur dan mendapan
Nature of solute – sifat zat terlarut
Nature of solvent – sifat pelarut
Neutralisation – penueutralan
Odourless - tidak berbau
Occurs - terjadi
Oil spill - tumpahan minyak
Particles - zarah
Potassium – kalium
Precipitate – mendakan
Preservation – pengawetan
Properties – sifat
Residue – baki/sisa
Saturated solution – larutan tepu
Sedimentation – pengenapan
Silt – lodak
Sodium – natrium
Solubility – kelarutan
Solute solution – zat larutan
Solvent – pelarut
Stronger - kuat
Suspension – ampaian/bahan terampa