Identifying and comparing materials Flashcards by Heinrich Nel

Why is the handle of a saucepan made from plastic?

Saucepan handles are made from plastic because plastic is a poor conductor of heat, so you won’t get burned when you touch the handle.

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Name the types of different materials

Metals
Plastics
Glass
Wood
Fabrics

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What are the different properties of metals?

Most metals are strong, hard and shiny materials that can be hammered into different shapes without breaking. They are good
conductors
of heat and electricity and some are magnetic. Their properties make them useful for objects such as cutlery, saucepans, cars and coins.

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What is an conductor?

A material which allows charge or heat to move easily through it.

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What are the different properties of plastics?

Plastics are materials made from chemicals and are not found in nature. They are strong and waterproof. They can be made into any shape by applying heat. Plastics are not magnetic. They are good
insulators
and don’t conduct heat or electricity. They’re used to make things like bags, bottles and toys

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What is an insulator?

insulator
A material that does not allow charge or heat to pass through it easily.

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What are the different properties of glass?

Glass is made by melting sand and other minerals together at very high temperatures. It is normally
transparent
and can be made into different shapes. Thick glass can be strong, but thin glass breaks easily. It’s used for objects that need to be transparent, such as windows and spectacles.

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What does transparent mean?

transparent
A material that we can see through, like glass, is transparent.

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What are the different properties of wood ?

Wood comes from trees. It is strong, flexible and long-lasting. It is an insulator of heat and electricity. It’s used to make things such as furniture.

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What are the different properties of fabrics ?

Fabrics are made from thin fibres woven together. Different fabrics have different properties. They can be stretchy (a pair of tights), insulating (a woollen coat) or
absorbent
(a towel). Fabrics are used to make clothes as they are flexible, warm and do not wear out easily.

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What is the meaning of absorbent?

absorbent
Materials that soak up, or absorb, liquids are absorbent.

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What is the meaning of Properties of materials?

Properties describe how a material behaves, and explain why it is well suited for a particular use. For example, metal has a high melting point (this is a property of most metals) so it is good to use to make a frying pan (this is the use of the material).

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What does it mean when a material is hard?

Hard

A material is hard if you cannot easily scratch it. Lots of metals are hard – you cannot easily scratch a metal pair of scissors.

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What does it mean when a material is transparent?

Transparent

A material is transparent if you can see through it. Glass is transparent. The opposite to transparent is opaque.

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What does it mean when a material is a good thermal conductor?

Good thermal conductors

Metals are good thermal conductors because heat passes through them easily. Fabrics are poor thermal conductors.

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What does it mean when a material is magnetic ?

Magnetic

Specific metals like iron and steel are magnetic because they can be attracted to a magnet.

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What is a property of most metals?

Good electrical conductor

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Which property of concrete explains why it is used to make road bridges?

It is strong

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Name a property of most plastics?

Waterproof

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Why is glass used to make windows?

It is transparent

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Why would it NOT be a good idea to make a frying pan out of plastic?

It would melt or burn

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Ways of separating substances

Sieving
Filtering
Evaporating

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Explain SIEVING

sieving
A way of separating solid substances using a mesh called a sieve, which allows the smallest particles to pass through, but not the largest particles

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Explain EVAPORATING

evaporating
When a liquid turns into a gas slowly, at temperatures below the boiling point.

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Explain FILTERING

Filtering A way of separating particles of a solid (e.g. sand) from a liquid (e.g. water).

When you separate a mixture of sand and water by passing it through a piece of filter paper . The water is able to pass through the tiny gaps in the paper but the sand particles are too big and are left on the surface of the filter paper. What is this process called?

Filtering

A mixture made of solid particles of different sizes, for example sand and gravel, can be separated by _________.

Sieving

How can water be separated from a salty solution?

Heating

By dissolving salt in water you make a solution. You can separate the salt from the water again by boiling the solution. The water will evaporate until it is all gone. The salt will be left behind. What is this process called?

Evaporating

How can a mixture of solid particles with different sizes be separated?

Sieving

You can use ____ to separate a sand and water solution and be left with both at the end.

filter paper

Examples of irreversible changes in HEATING

Heating can cause an irreversible change. For example you heat a raw egg to cook it. The cooked egg cannot be changed back to a raw egg again.

Examples of irreversible changes in MIXING

Mixing Mixing substances can cause an irreversible change. For example, when vinegar and bicarbonate of soda are mixed, the mixture changes and lots of bubbles of carbon dioxide are made. These bubbles and the liquid mixture left behind cannot be turned back into vinegar and bicarbonate of soda again.

Examples of irreversible changes in BURNING

Burning is an example of an irreversible change. When you burn wood you get ash and smoke. You cannot change the ash and smoke back to wood again.

A reversible change is a change that can be undone or reversed such as:

dissolving melting freezing evaporation mixing

If you can get back the substances you started the reaction with, that's a ____________

REVERSIBLE REACTION, for example: water can be frozen and turns into ice but if you heat the ice it melts back to water.

What type of change is freezing?

Freezing is a reversible change. For example you can freeze juice to make ice lollies. The lollies can be changed back into juice by heating.

If a change is called irreversible if it __________

it cannot be changed back again

Many _________reactions are irreversible.

chemical

Is cooking an egg a reversible change?

Burning is an irreversible change, which means it ___.

can't be reversed

An irreversible change is ___.

permanent

Which of these is NOT an irreversible change? Burning paper Freezing water Baking a cake

Freezing water

When we need to choose a material for a particular job, we do experiments to find out which material will have the best _______.

Properties

Define properties?

properties The qualities a material has to describe it and its suitability for different purposes.

What term is used to describe an experiment where different materials are compared but all the other variables are kept the same?

Fair test

When investigating the strength of different materials used to make a rope by hanging weights from it, what should you keep the same?

The thickness of the rope

You can test out different designs for a bridge using paper straws and sticky tape. What are the most important things to keep the same to make this a fair test?

The number of straws used in each design

When you add some sugar to water and stir, what does the water taste like? Can you explain why?

The water tastes sweet because the sugar is still there, even if you can’t see it because it has dissolved.

When a substance dissolves, it might look like it has disappeared, but in fact it has just mixed with the water to make a transparent (see-through) liquid called a ________

solution

Substances that dissolve in water are called ____________. When you mix sugar with water, the sugar dissolves to make a transparent solution. Salt is soluble in water too.

soluble substances

Substances that do not dissolve in water are called _____________. When you mix sand or flour with water, they do not dissolve.

insoluble substances

__________can help some substances dissolve faster in water. Salt, for example, will dissolve quicker in hot water than in cold water.

Heat

Will wax dissolve in water?

What will happen if you put sugar in water and you stir it?

When you put sugar into water and stir it up, the sugar will seem to melt away. The water looks clear and you won't be able to see the white sugar any more. This is because the sugar has dissolved. Hot water will make the sugar dissolve faster.

What will happen if you put sand in water and you stir it?

If you put sand into water and stir it up, the water will go dark and cloudy. If you stop stirring the mixture and leave it alone for a short time, you will soon see tiny grains of sand sinking down to the bottom of the water. After a short time, all the sand will be at the bottom of the beaker and you will have clear water at the top. This is because sand does not dissolve.

Some substances ______ when you mix them with water.

dissolve

When dissolving salt in water. This process makes a transparent liquid called a ________ .

solution

Substances that don't dissolve in water are called ________ substances.

insoluble

______ is an example of a soluble substance.

Salt

True or false: when a soluble substance, such as salt, dissolves in a liquid it has disappeared.

False

Sugar ___ in water.

dissolves

What two ways could you do to make a substance dissolve faster in water?

Heat it up stir it quicker

What word describes substances that dissolve in water?

Soluble

A change is called irreversible if it cannot be changed back again. Many _____________ are irreversible.

Chemical reactions

A reversible change is a change that can be undone or reversed such as:

dissolving melting freezing evaporation mixing

If you can get back the substances you started the reaction with, that's a _________ reaction, for example: water can be frozen and turns into ice but if you heat the ice it melts back to water.

If you can get back the substances you started the reaction with, that's a reversible reaction, for example: water can be frozen and turns into ice but if you heat the ice it melts back to water.

A reversible change might change how a material ______ or _______. It sometimes creates new materials.

looks or feel

_________ is a reversible change. For example you can freeze juice to make ice lollies. The lollies can be changed back into juice by heating.

Freezing

It is important to make our experiments ________. This usually means keeping things the same when you are comparing the different materials, so it is a fair comparison.

fair

What term is used to describe an experiment where different materials are compared but all the other variables are kept the same?

Fair test