Name:
Class:
Chapter
14
Worksheet 14.1
Date:
Changing Matter
For Science Matters Textbook Volume A, sections:
14.1
Observing Changes
14.4
Interactions between Matter and Light
14.2
Types of Changes
14.5
Interactions between Matter and Electricity
Interactions between
14.6
14.3
Matter and Heat
Interactions between Matter – Mixing
Substances
Secure Your Basics
Without referring to the textbook, try to answer these questions. If you cannot
answer a question, look up the relevant section in your textbook.
1.
Which of the following processes involves a chemical change?
A
B
water
out
water
in
C
D
(
2.
C
)
B
)
Which of the following word equations does not show thermal decomposition?
A
Calcium carbonate
B
Carbon + Oxygen
C
Copper carbonate
D
Sugar
heat
heat
heat
heat
Calcium oxide + Carbon dioxide
Carbon dioxide
Copper oxide + Carbon dioxide
Carbon + Water vapour
©
© 2007
2008 Marshall
Marshall Cavendish
Cavendish International
International (Singapore)
(Singapore) Pte
Pte Ltd
Ltd
(
Changing Matter
131
3.
When iron filings are added to sulphur powder and heated, the reaction is
.
A
C
4.
called combination
called decomposition
called combustion
reversible
contraction of an iron bar
heating up irons and cookers
B
D
A
)
.
decomposing water
operating an electromagnet
(
A
)
Complete the following table by the name of the process described.
Description of process
Name of process
Burning bottled gas for outdoor cooking
Combustion
Iron rusting in the presence of water and oxygen
Combination
Sugar being heated strongly
Decomposition
Water being broken down into its elements by electricity
Electrolysis
Water puddle slowly disappearing under sunlight
Evaporation
Metal cap on bottle becoming looser when hot water is
poured over it
6.
(
Electricity can cause the following effects except
A
C
5.
B
D
Expansion
Explain how the following processes take place. Explain whether they are physical
or chemical processes.
a)
Producing light in a light bulb
The filament in the light bulb is heated up, and electrical energy is
converted to heat and light energy. No new substances are formed — it
is a physical change.
b)
Making electromagnets
A direct electric current passes through wire wound many times over an
iron bar. It is reversible as temporary magnets only produce a magnetic
effect when the current is switched on — it is a physical change.
132
Changing Matter
© 2008
2007 Marshall Cavendish International (Singapore) Pte Ltd
7.
Describe three ways in which light can cause useful changes in our daily life.
Photosynthesis — plants use light to make food, which in turn gives us food.
Photography — light causes chemical changes on photographic film, giving us photographs.
Obtaining energy from solar cells — light is converted into electricity.
8.
State whether each of the following chemical changes is caused by electricity, light,
heat and mixing of substances.
Chemical change
Coating chromium on a water tap
Electricity
Green plants making food
Light
Magnesium forming magnesium oxide in air
Heat
Formation of carbon dioxide
9.
Cause
Mixing of substances
Complete the following table with the type of change involved in each process.
Process
Change
a)
Cooking meat
Chemical
b)
Extracting aluminium from aluminium ore
Chemical
c)
Boiling water
Physical
d)
Photosynthesis
Chemical
e)
Exposing photographic film to light
Chemical
f)
Iodine crystals turning into iodine gas
Physical
©
© 2007
2008 Marshall
Marshall Cavendish
Cavendish International
International (Singapore)
(Singapore) Pte
Pte Ltd
Ltd
Changing Matter
133
Map It Out
Complete the graphic organiser that follows the question below.
Compare the combustion of carbon (charcoal) and the sublimation of dry ice (carbon
dioxide). State which one is chemical or physical change.
Combustion of charcoal
Sublimation of dry ice
Similarities
•
•
•
heat
In both process,
is required.
Both processes produce carbon dioxide gas.
Starting materials for both processes are solids.
Difference
New substances
are formed,
namely carbon dioxide and
water vapour.
Chemical
No new substance is formed.
Solid carbon dioxide turns into
gaseous carbon dioxide.
Physical
change
change
From the above graphic organiser, we can conclude that both physical and chemical
changes may involve
heat
formation of new substances
134
Changing Matter
. However, only chemical changes involve
.
© 2008
2007 Marshall Cavendish International (Singapore) Pte Ltd
Challenge Yourself
• 20 min •
Attempt the following questions within the time allocated.
1.
The combustion process does not necessarily involve
A
B
C
D
2.
(
B
)
Carbon dioxide
Carbon monoxide
Heat
Oxygen
(
B
)
When substances are mixed, a chemical change may take place. Which of the
following does not result in a chemical change?
A
B
C
D
4.
a chemical change
a fuel
presence of heat
presence of oxygen
Which substance is not present during complete combustion of fuels?
A
B
C
D
3.
.
Adding sulphuric acid to magnesium
Adding salt to a soft drink
Adding vinegar to baking powder
Adding yeast to dough
(
B
)
Both sugar and copper carbonate undergo decomposition when they are heated
strongly.
a)
Write down the word equations for the reactions.
Sugar
heat
Carbon + Water vapour
Copper carbonate
b)
heat
Copper oxide + Carbon dioxide
State the observations for these two reactions.
White sugar crystals melt and turn into a brown liquid before turning into a black solid. Colourless
water droplets are formed on sides of the test-tube.
Green copper carbonate powder turns into a black powder.
©
© 2007
2008 Marshall
Marshall Cavendish
Cavendish International
International (Singapore)
(Singapore) Pte
Pte Ltd
Ltd
Changing Matter
135
5.
When an acid (hydrochloric acid) is added to an alkaline solution (sodium hydroxide),
the resulting solution becomes warm. Two substances are formed, sodium chloride
and water. This reaction is known as neutralisation.
hydrochloric
acid
retort
stand
conical
flask
sodium hydroxide
solution
a)
Give two explanations to show that neutralisation is a chemical change.
New substances are formed. Heat is given out to the surroundings (the solution feels warm).
b)
In neutralisation, what kind of interactions is involved?
Interactions between matter and another matter, i.e. between substances.
c)
Complete the word equation below.
Hydrochloric acid + Sodium hydroxide
d)
Sodium chloride + Water
To obtain the salt, the mixture of sodium chloride and water is then evaporated
to dryness in an evaporating dish. Is “evaporation to dryness” a physical or
chemical change? Why?
It is a physical change. The water is lost as water vapour — this is a change in state and no new
substances are formed.
136
Changing Matter
© 2008
2007 Marshall Cavendish International (Singapore) Pte Ltd
Name:
Class:
Worksheet 14.2
Date:
For Science Matters Textbook Volume A, section:
14.7
Chemical Changes – Friends or Foes?
Secure Your Basics
Without referring to the textbook, try to answer these questions. If you cannot
answer a question, look up the relevant section in your textbook.
1.
Air pollutants cause the following except
A
B
C
D
2.
.
heavy traffic congestion in cities
making water bodies unsuitable for organisms
physical corrosion of buildings
respiratory problems in living things
( A )
List the products that are released to the surroundings during combustion of fuels
in vehicles, power stations and factories. Which of them are air pollutants?
Carbon dioxide and water vapour, by-products such as carbon monoxide and soot (unburnt carbon),
sulphur dioxide, oxides of nitrogen.
Pollutants include carbon monoxide and soot (unburnt carbon), sulphur dioxide, and oxides of nitrogen.
3.
Group the following into useful or not useful processes.
rusting
respiration
photosynthesis
combustion of fuels in power stations
extracting iron from iron ore
combusion of fuels producing air pollutants
Useful
Photosynthesis
Combustion of fuels in power stations
Digestion
Respiration
Decay of dead organisms
Extracting iron from iron ore
Making electromagnets
Electroplating
©
© 2007
2008 Marshall
Marshall Cavendish
Cavendish International
International (Singapore)
(Singapore) Pte
Pte Ltd
Ltd
digestion
forest fires
electroplating
decay of dead organisms
making electromagnets
Not useful
Rusting
Combustion of fuels producing air pollutants
Forest fires
Changing Matter
137
Challenge Yourself
• 10 min •
Attempt the following questions within the time allocated.
1.
Which of the following is not a useful process?
A
B
C
D
2.
Combustion of fuel in car engines
Decay of dead organisms
Electroplating metallic objects
Production of sulphur dioxide from power stations
(
D
)
Why is the decay of dead organisms an important and useful chemical change?
It returns nutrients back to soil to be recycled for use naturally by plants, otherwise dead organisms
would be found everywhere and there would not be enough space on earth to bury them.
3.
Steven thinks that a chemical reaction always requires at least two reactants or
produces at least two products.
a)
Give an example to show that this is not true.
Magnesium burns in air forming magnesium oxide. / Carbon burns in air to form carbon dioxide. /
Sugar decomposes by heating to produce water and carbon.
(Accept any other reasonable answers.)
b)
Give an example where two reactants react to form exactly two products. Write
the word equation for it.
Photosynthesis; Carbon dioxide + Water
Glucose + Oxygen
Neutralisation; Hydrochloric acid + Sodium hydroxide
Water + Sodium chloride
(Accept any other reasonable answers.)
138
Changing Matter
© 2008
2007 Marshall Cavendish International (Singapore) Pte Ltd
Get It Right
Below is a simple diagram of the stages involved in a power station.
power lines
heat from
burning fuels
steam
turbine
generator
water (condensed
from steam)
water
a)
State and explain two physical changes that take place in the power stations.
Boiling and condensation. When water boils, it changes from liquid to gas. When steam condenses, water
changes from gas to liquid. The substance is still water; there is no new substance formed.
b)
State and explain a chemical change that occurs in the power station.
Combustion of fuels. When burnt, fuels (e.g. carbon compounds) are changed to other substances such
as carbon dioxide and water vapour.
Analyse each process that takes place in a power station. Identify which ones involve
physical or chemical changes. Refer to the Science Matters Textbook Volume A, chapter
14 on Changing Matter to help you.
©
© 2007
2008 Marshall
Marshall Cavendish
Cavendish International
International (Singapore)
(Singapore) Pte
Pte Ltd
Ltd
Changing Matter
139
c)
There are also energy changes/transfer taking place in the power station. Briefly
explain the energy change/transfer that occurs in each of the following:
i)
Furnace
Chemical energy in fuel is changed to heat by combustion.
ii)
Boiler
Heat causes the water particles to have more kinetic energy and turns into moving
steam, which has kinetic energy.
iii) Turbine
The turbine transfers kinetic energy of the moving steam to the generator.
iv) Generator
Kinetic energy from the turbine turns the generator. Kinetic energy of the generator is changed to
electricity.
Refer to the Science Matters Textbook Volume B, section 16.3 on Energy Transformations.
140
Changing Matter
© 2008
2007 Marshall Cavendish International (Singapore) Pte Ltd