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Materials

Grade6, Unit 6M.4:

Heating and burning

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

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 smoke(gases) tin can

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

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) = (temporary change)

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Materials

Grade6, Unit 6M.4:

Heating and burning

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.

86

Materials

Grade6, Unit 6M.4:

Heating and burning

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

Jar A B C

Time

Conclusions : ----------------------------------------

-----------------------------------------------.

A C B

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Materials

Grade6, Unit 6M.4:

Heating and burning

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

Type of causing fire:

Class A Ordinary Combustibles

Class B Flammable and combustible liquids

Class C Flammable gases

Class D Combustible metals

Class E electrically energized equipment

Class 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!

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Materials

Grade6, Unit 6M.4:

Heating and burning

Type of FIRE Wood fire Electrical Fire Oil fire

Which type of

extinguisher

would you use?

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.

90

Materials

Grade6, Unit 6M.4:

Heating and burning

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.

6.12.3

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

Which type of changes happened in this activity?

________________________________________________

Which material changed the most? _____________________

Which type of changes happened in this activity?

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?

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.

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Materials

Grade6, Unit 6M.4:

Heating and burning

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!

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Materials

Grade6, Unit 6M.4:

Heating and burning

Examples of physical and 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!

We can get the sugar

back boiling ALL the tea

away!

We can get the water

back by making it touch

a cold surface

We can change the

melting ice lolly back by

freezing it again!

Chemical changes!

Physical

changes!

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Materials

Grade6, Unit 6M.4:

Heating and burning

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

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Materials

Grade6, Unit 6M.4:

Heating and burning

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.

_________________________________________________

_________________________________________________

_________________________________________________