67

Materials

Grade6, Unit 6M.3:

Changing materials

Unit 6M.3: Changing materials

Adding materials to water.

Chemical reactions

Skill you will use:

Classifying

Observing

Predicting

By the end of this unit you should:

Know that when substances are added to water, some

will react while others either dissolve or remain suspended.

Distinguish between reversible and irreversible changes

and know that reversible changes are physical and

irreversible ones involve chemical changes in which new

substances are formed.

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Materials

Grade6, Unit 6M.3:

Changing materials

Mixing materials to water

Many types of materials dissolve when

mixed into water, this forms a solution.

Salt is a soluble material, it dissolves in

water. A material that doesn’t dissolve in

water is called insoluble, for example sand.

A material that is insoluble creates a suspension when mixed

in water. A suspension is not clear, you cannot easily see

through it. As the large, insoluble particles settle you can

see the separate layers.

Physical changes in water are temporary and reversible

Some materials can react with water, like

sodium. Signs of a chemical change in

water are the presence of bubbles, change

in colour, light or heat, even a flame.

6.12.1, 6.12.2

Muddy water

particles are

suspended in

water making

it cloudy

The large mud

particles have

settled to bottom

69

Materials

Grade6, Unit 6M.3:

Changing materials

Activity 1: Investigate what happens when a variety of

substances are added to water.

You will need:

Five 500 ml plastic bottles with caps

Teaspoon

Plastic funnel

Samples: sugar, dirt, tea leaves (cut

open a tea bag), flour, food colouring

Water and measuring beaker

Steps:

1. Use the funnel to add 1 teaspoon of each of the sample

to the empty plastic drink bottle.

2. Predict (P) what will happen to each sample after the

water is added:

Sugar……………………………………………………………………………………….…………..

………………………………………………………………………………………….…………………….

Dirt…………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

Tea leaves……………………………………………………………………………………………

…………………………………………………………………………………………………………………

Flour……………………..………………………………………………………………………………

…………………………………………………………………………………………………………………

Food colouring………………………………………………………………………………………

…………………………………………………………………………………………………………………

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Materials

Grade6, Unit 6M.3:

Changing materials

2. Use the measuring beaker and funnel to add 250ml of

water to each plastic bottle and screw on the lid.

3. Observe (O) what happens to contents initially.

4. Now, shake each bottle until the contents are mixed.

5. Choose some key changes you observed to add to the top

line of the Attribute List Organiser (ie dissolved, suspended,

cloudy etc).

6. Record the changes that you observed for each sample by

placing ticks in the corresponding box. You can also draw

examples. Attribute List Organiser

Sample Change 1

………………………

Change 2

………………………

Change 3

………………………

Change 4

………………………

Sugar

Dirt

Tea

leaves

Flour

Food

Colouring

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Materials

Grade6, Unit 6M.3:

Changing materials

Observe (O): Other observations you want to comment on?

………………………………………………………………………………………………………………….

………………………………………………………………………………………………………………….

…………………………………………………………………………………………………………………

Explain (E): Did your observations match your predictions?

Did anything happen that you did not predict?

……………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………

Activity 2: Sort into a T-chart the following common kitchen

materials according to how they change when added to water

Milo, detergent, pepper, milk, salt,

juice, rice, coffee granules, cooking oil.

Dissolves Suspended

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Materials

Grade6, Unit 6M.3:

Changing materials

Changing Materials with Water:

1-Weathering is the process of breaking down a material

over time. There are two types of weathering; physical

weathering and chemical weathering.

Physical weathering erodes a

material over time, but the

properties of the material stay

the same.

Chemical weathering also breaks

down a material over time but it

changes the properties that the

material is made of. For instance,

a hard material may change to a

soft material after chemical weathering.

The time taken for the weathering process depends on the

properties of the material, the amount of water, the

movement/ action and the type of water.

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Materials

Grade6, Unit 6M.3:

Changing materials

2- Extracting colour: The colour

found in our soils and rocks, plant

leaves and flowers can be extracted

using water. If you collect a sample

of soft rock and scratch the surface to make a powder. Mix

the powder with water it can make a paint known as ochre.

Traditionally tribes used the ochre pigment for art.

3- Extracting scent: The natural

oils in plants, fruits and flowers

have a scent that can be

extracted using water. The

water is used to heat and reduce

down the liquid from the plant.

The liquid left produced in this

process has a fragrance that is

used for perfumes and fragrances.

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Materials

Grade6, Unit 6M.3:

Changing materials

Aerial Water Bombing

Foam Extinguisher

4- Putting out fires: Water has two main properties that

help put out certain types of fires.

Water when applied to a very

hot fire changes to steam, this

steam prevents the air getting

to the fuel thus putting out the

fire.

The water also cools the fuel

to below the ignition point

helping to put out the fire.

Water only helps for fires of

paper, wood or cloth/ material.

Other types of fires may need

chemicals to extinguish the

flame for eg. petrol.

75

Materials

Grade6, Unit 6M.3:

Changing materials

Chemical Changes of Materials

A chemical change is when the atoms in a substance or

material link together to make a new substance. This is

known as a chemical reaction. The properties of the original

material have changed.

Chemical changes can be permanent and irreversible but

like physical changes they can also be reversible.

You can usually identify when a chemical change of a material

has taken place if:

- a gas or smell is given off

- there is permanent color change

- a new substance (e.g. rust) is formed and is visible

- the liquid changes temperature

- the solute is not recoverable when the water is left to

evaporate.

These children are studying chemical

reactions that make materials change

permanently.

The substances they start with are

called reactants. After the reactants

change, they form a new substance

called a product.

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Materials

Grade6, Unit 6M.3:

Changing materials

Activity 3: Observing a Chemical Reaction

You will need:

Plastic bottle, Baking soda, teaspoon, balloon, funnel,vinegar.

Steps:

1. Use the funnel to add 2 teaspoons of baking soda to the

balloon.

2. Tip a small amount of vinegar into the bottom of the

plastic bottle.

3. Attach the balloon to the top of the plastic bottle,

CAREFUL not to tip the contents in yet!

4. Draw a picture of what the experiment looks like BEFORE

in the box below.

5. Now tip the contents of the balloon, the baking soda into

the bottle.

6. Draw another picture of the experiment AFTER adding

the baking soda.

BEFORE

AFTER

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Materials

Grade6, Unit 6M.3:

Changing materials

What evidence do you have that the Baking soda and vinegar

experienced a chemical change?.....................

………………………………………………………………………………………………………………

………………………………………………………………………………………………………………

………………………………………………………………………………………………………………

………………………………………………………………………………………………………………

Design your own experiment

using baking soda and vinegar to

demonstrate a chemical change.

Remember the scientific process

Show your experiment design

and planning to the teacher

before you test it out.

Write some initial ideas down

here:

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Materials

Grade6, Unit 6M.3:

Changing materials

Using electricity to change things: Water and solutions, particularly strong salt solutions or acid

solutions, like lemons are known as conductive substances.

This means that electricity flows through them easily.

Why cells and batteries eventually

run down when used?

A chemical cell converts chemical

energy into electrical energy. Most

batteries are chemical cells. A

chemical reaction takes place inside

the battery and causes electric

current to flow. This process is

known as electrolysis.

Research the “Lemon Juice

Electricity Experiment”

What are the procedures?

How does it work?

Test it out yourself!

79

Materials

Grade6, Unit 6M.3:

Changing materials

Key Terms: Soluble/

insoluble

Dissolve

Suspension

Physical and

chemical change

Weathering

Permanent

Temporary

Key Ideas: Some materials when added to water

dissolve and others form suspensions.

Materials can have physical or chemical

change.

Sometimes change in some materials is

temporary and other times permanent.

Chemical changes can create new

substances.

Key Questions:

Q1 Complete this concept map for the word “Dissolve”

DISSOLVE

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Materials

Grade6, Unit 6M.3:

Changing materials

Q2. Amal added some substances to water and stirred them.

She noted her observations in the table below.

Substance Observation

1 - Sugar Dissolved

2 - Salt Dissolved

3 - Sand Remained at the bottom

4 - Stomach powder Bubbles of gas given off

5 - Flour Liquid turned white and eventually the white

substance collected at the bottom

What substances experienced chemical changes?

……………………………………………………………………………………………………………………….

b. How could Amal tell if it was a chemical change?

………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………..

c. Which two samples could the change have been physical or

chemical?............................................................

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Materials

Grade6, Unit 6M.3:

Changing materials

Q2: The two lists below contain raw materials and substances

made from them. Draw lines to connect each raw material to

the substance produced from it. On each line write whether

the change is a physical or a chemical one.

Raw material Substance produced

Clay Glass

Ore Metal

Sand Paper

Seawater Pottery

Wood Salt

Q3: Classify the list of changes as physical or chemical

change

A. Making yoghurt from milk. ---------------.

B. Making drink cans from aluminium sheet. -----------.

C. Boiling water in a kettle. -------------.

D. Boiling an egg. -----------.

E. Making a cup of tea. ---------------.

F. Using a torch cell. ---------------.

G. Burning a candle. ---------------.