Materials
Unit 6M.4: Heating and burning
 Burning
 Heating different
materials
Skill you will use:
 Classifying
 Observing
 predicting
By the end of this unit you should:
–
Classify changes into reversible and
irreversible changes.
–
Distinguish between heating and burning, and
that heating can bring about temporary,
physical changes in some materials and
permanent chemical changes in others.
82
Grade6, Unit 6M.4:
Heating and burning
Materials
6.12.1
HEALTH and SAFETY
Make sure you warn kids not to touch the hot
wax or flame!
Make sure kids are not close to the flame when
observing
Make sure all flammable fabrics (shimagh/hijab)
are kept away from the flame.
Burning
Candle Experiment
Aim:
To see what happens to the material wax when it burns.
Equipment:
 Candle
 Matches
 Plastic (inflammable) board to stand it on
 Piece of metal or test tube
Method:
Light the candle and observe what happens as it burns, make
note of what changes occur. When the candle is burning using a
tong and place a tin can above the flame – see what happens to
it – use a tissue to see !
Diagram: Draw how your teacher sets up the equipment.
Use these words to label the picture:
candle(wax)
wick
flame
liquid wax
83
smoke(gases) tin can
Grade6, Unit 6M.4:
Heating and burning
Materials
Results (what happened):
----------------------------------------------------------------------------------------------------Use these words to fill in the gaps:
gases
smoke
wax
water vapour
liquid
black
 As the wick burnt it heated the ______ which melted and
became liquid wax.
 The liquid wax burnt and _________ were released into
the air. We saw this as a black substance.
 The candle wax material changed into a _________ and
was burnt when it was heated with a flame.
 The wick became _________ and shorter.
When you light a candle, the part of candle
near the flame gets hot and melts.
The wax has changed state, but it is still the same substance.
When it cools down, you get the solid wax back.
This is a Physical change, generally changes like this are
reversible.
Physical changes (shape or state) =
84
(temporary change)
Grade6, Unit 6M.4:
Heating and burning
Materials
When you light a candle, you light the ‘wick’ of the candle (this
is the string in the middle of the wax candle) …it usually looks
like this:
As it burns it becomes shorter and changes colour.
When the wick burns This type of change is called a chemical
change. Chemical changes are not easily reversible.
Chemical change = (New substance) = (Permanent change)
You know it is a chemical change if,
- A new substance is formed.
- Or, the change cannot be reversed.
85
Grade6, Unit 6M.4:
Heating and burning
Materials
Activity:
What does a substance need to burn?
You will need:
 Three small candles
 Three different sized jam jars or
drinking glasses.
 Stop watch.
 Matches.
 Bluetak (to hold candle in place)
Steps:
Burn three small candles under jam jars of different sizes and
record how long the flame takes to go out.
Use a stopwatch and record your data.
Predict – which candle will expire first?-------------------
AA
A
B
C
Jar
A
B
C
Time
Conclusions : --------------------------------------------------------------------------------------.
86
Grade6, Unit 6M.4:
Heating and burning
Materials
Burning is a permanent change that cannot be reversed.
It is an example of a chemical change.
Burning happens only if there is fuel and oxygen.
As a result, a new chemical is formed.
Fuel + oxygen
new substance + energy
Fire is one of the most common hazard that one faces. A fire
extinguisher is an active fire protection device used to
extinguish or control small fires.
In laboratories and houses, we have different types of
extinguishers according to the type of the fire. For example if
it caused by electricity or chemicals, then a foam or CO2
extinguisher will be used.
87
Grade6, Unit 6M.4:
Heating and burning
Materials
Type
Class
Class
Class
Class
Class
Class
of causing fire:
A Ordinary Combustibles
B Flammable and combustible liquids
C Flammable gases
D Combustible metals
E electrically energized equipment
F Cooking oils and fats
The most common types of extinguishers are:
Water - solid red – A
Foam - red with a light yellow band or label - A,B,C
Powder - red with a blue band or label - B,C
Carbon Dioxide (CO2) - Red with a black band or label – E –
here you can see we would not use water! As water on an
electric fire might makes it worse, and even electrocute you!
88
Grade6, Unit 6M.4:
Heating and burning
Materials
Type of FIRE
Which type of
extinguisher
would you use?
Wood fire
Electrical Fire
Oil fire
Fire Hazard:
A fire hazard is any situation in which there is a greater than
normal risk of harm to people or property due to a possible
fire. Fire hazards include things which, in the event of fire,
pose a hazard to people, such as materials that produce toxic
fumes when heated or objects that block fire exits.
Fire safety tips:
1- Install smoke detectors.
2-
Use Electricity Safely
3-
Be Careful when cooking.
4-
Have a fire blanket handy.
89
Grade6, Unit 6M.4:
Heating and burning
Materials
There is another way to put
out fires. Especially for the
kitchen where you don’t
want to spill burning oil for
example.
USE a FIRE BLANKET
A Fire blanket works by
smothering the fire –
stopping the Oxygen
getting to the fire.
6.12.3
Heating different materials
Heating can cause temporary changes in some materials and
permanent changes in other materials.
A. Here are some examples of temporary changes caused by
gentle heating: (physical changes):
Heating butter, chocolate and wax will raise the temperature.
They all change from solid to liquid. We say that they have
melted. Melting is a temporary, physical change.
When they cool down again, they change back to solids.Melting
is a temporary change.
90
Grade6, Unit 6M.4:
Heating and burning
Materials
B. Permanent changes caused by high temperature :
a. Sugar melts at oven temperature, and then starts to
change into brown (caramel). When caramel cools it
becomes solid. This is a permanent change.
Mix water and sugar
(with some corn syrup) & HEAT
b. Eggs baked inside the oven is an example of
permanent change as well
Activity: Chemical and physical change
Some substances change when the temperature rises only
slightly. When you do this activity, don’t touch the lamp
You will need:
Aluminum foil, chocolate, cube of butter, wax or trays, electric
lamp, straws, butter and sugar.
91
Grade6, Unit 6M.4:
Heating and burning
Materials
Steps
1-Cut out four 10 cm squares of aluminum foil.
Fold up the edges and pinch the corners to make
four small boxes with an open top and a flat
bottom.
2-Put a small amount of each substance into the
aluminum boxes so that each box contains something
different.
3-Ask an adult to switch on the lamp and point it
straight downwards, about 5 cm above the boxes.
Wait for at least five minutes to see how heat from
the lamp affects the different substances.
4- Switch off the lamp and move it away from the
boxes.
Now stir each of the substances with the straw to
see how they have changed let them cool.
92
Grade6, Unit 6M.4:
Heating and burning
Materials
Which type of changes happened in this activity?
________________________________________________
Which material changed the most? _____________________
Bake a model
Mould some modeling clay (that you can bake) into
a shape to make a model. Think about how it looks
and what it feels while you do this. Then ask an
adult to bake your model in the oven. Let it cool.
How does it look and feel now?
Which type of changes happened in this activity?
Frying eggs: (Teacher demonstration)
1- Crack a raw egg into the frying pan.
2-
Flip the egg over when ready.
3-
Remove the egg from the pan and eat!
The egg tasted much better cooked than it
would if had been eaten it raw. This is because
the heat caused the egg to change. The egg
cannot be changed back, a chemical change has
taken place and the egg changed forever.
93
Grade6, Unit 6M.4:
Heating and burning
Materials
Which type of changes happened in this activity?
____________________________________________
Materials and Changes - Investigation
You will need:
Wood, paper, cotton, plastic, metal, clay, wool, stone, wax and
candle.
Material
Heating
by fire
Wetting
with
water
Bending
Twisting
Squashing
Stretching
Wood
Paper
Cotton
Plastic
Metal
Clay
Wool
Stone
Wax
Steps:
Complete this table above by stating if the
change is REVERSIBLE or IRREVERSIBLE:
 Candle – only put the material above the
flame for 10sec!
 Metal tongs
 Bowel of water
 Strong pair of hands!
94
Grade6, Unit 6M.4:
Heating and burning
Materials
Examples of physical and chemical changes
Chemical
changes!
When this tablet is added
to water a gas, carbon
dioxide, is made.
We can’t get that tablet
back again!
After making the plaster,
the liquid is rubbed over the
broken wrist. The plaster
becomes hard as it dries and
a new substance is made.
We can’t make it back into a
liquid!
Coal and wood produce
gases, which go up the
chimney, and ash, which is
left behind.
We can get the wood back!
Physical
changes!
We can get the sugar
We can get the water
back boiling ALL the tea back by making it touch
away!
a cold surface
95
We can change the
melting ice lolly back by
freezing it again!
Grade6, Unit 6M.4:
Heating and burning
Materials
Key Words: Physical change, Chemical change, Permanent,
Temporary, Heat, Burning.
Key idea
 Physical change =Reversible change =Temporary change
 Chemical change =Irreversible change =Permanent change
Heating can bring about temporary, physical change in some
materials and permanent, chemical, changes in others.
 Burning is a chemical change.
Key questions:
1-
Classify the above picture into chemical and physical
change, and explain why to your partner?
Chemical change
Physical change
96
Grade6, Unit 6M.4:
Heating and burning
Materials
2-a.There are many different kinds of fire extinguishers, but
they all put out the fire in the same way. Explain how the
material in a fire extinguisher puts out the fire.
_________________________________________________
b. What is the best way of putting out the following fires?
Explain your answer to your partner:
i. A fire in a car.___________________________________
ii. A fire in a kitchen caused when cooking oil catches fire.
________________________________________________
iii. A pool of burning methylated sprits.
________________________________________________
3-a. When a candle burns, the wax changes into products
that are gases. Explain how you could detect one of those
products. Explain what it is.__________________________
________________________________________________
b. If two identical candles are lit and one is then covered
with a large jam jar and the second with a small one they
both will go out. Which one will go out first?
_________________________________________________
_________________________________________________
c. Explain why they both are extinguished and why one is
extinguished before the other.
_________________________________________________
_________________________________________________
_________________________________________________
97
Grade6, Unit 6M.4:
Heating and burning