Physical Properties Of Materials

Question 1

What is compressive strength?

Answer 1

Strength of an object that stops it from being crushed, or changing shape when it is pushed or squeezed

Question 2

What is tensile strength?

Answer 2

Strength of an object that stops it from breaking when it is pulled apart

Question 3

What is flexibility?

Answer 3

Ability to bend easily

Question 4

Give three examples of materials with compressive strength.

Answer 4

Concrete
Rocks
Bricks

Question 5

Give and example of a material with tensile strength.

Answer 5

Steel

Question 6

What can flexible materials do?

Answer 6

Bend without breaking

Question 7

Give an example of a flexible material.

Answer 7

Rubber

Question 8

Give three examples of when we use flexible materials.

Answer 8

. A rubber garden hose to water the garden
. Car tyres
. Fabrics for clothes

Question 9

What does melt mean?

Answer 9

When a substance changes from a solid to a liquid

Question 10

Define melting point.

Answer 10

Temperature at which a substance melts as it changes from a solid to a liquid

Question 11

What does boil mean?

Answer 11

When a liquid starts to bubble and change into a gas

Question 12

Define boiling point.

Answer 12

Temperature at which a liquid turns into a gas

Question 13

What are electrical conductors?

Answer 13

Materials that allow electricity to move through them

Question 14

What are electrical insulators?

Answer 14

Materials that do not allow electricity to move through them

Question 15

Define electrical conductivity.

Answer 15

Ability of a material to allow electricity to move through it

Question 16

At what temperature does ice melt?

Answer 16

Around 0°C
We call this the melting point of ice

Question 17

At what temperature does water boil?

Answer 17

Around 100°C
We call this the boiling point of water

Question 18

Notice that we say ‘around’ 0°C or 100°C. This os because conditions are not identical at all times. What can be different? Give an example.

Answer 18

Pressure and impurities, such as chemicals in the water, make a difference to melting and boiling points. For example, water boils at about 96°C in Johannesburg because of the lower air pressure there

Question 19

Which metal has the highest boiling point?

Answer 19

Tungsten has the highest boiling point (5555°C)

Question 20

What do we use electrical conductors for?

Answer 20

We use the property of electrical conductivity pf materials like copper and aluminum to make electrical wiring

Question 21

What do we use electrical insulators for?

Answer 21

Electricity can be very dangerous so we use materials with the electrical insulation property such as rubber and plastic to protect and cover the electrical wires

Question 22

What is heat conductivity?

Answer 22

Ability of a material to allow heat to flow through it

Question 23

What is thermal conductivity?

Answer 23

A synonym for heat conductivity

Question 24

What are thermal insulators?

Answer 24

Materials that prevent heat from flowing through them or that reduce the rate at which heat flows through them

Question 25

What are variables?

Answer 25

Factors that can change, are observable and measurable

Question 26

Give an example of how both thermal conductors and thermal insulators can be used in every day life.

Answer 26

If you are cooking in a pot on the stove, the pot is usually made of metal such as copper or aluminum (metal conducts heat), but the handle is usually made of wood ar hard plastic (wood and plastic are thermal insulators)

Question 27

What happens to the temperature of water once it has reached its boiling point?

Answer 27

It does not continue increasing. It will continue boiling at the same temperature until all of it has evaporated

Question 28

What other factors are taken into consideration when selecting suitable materials?

Answer 28

Appearance, style, colour, texture and cost. We cannot always combine all the factors that we want so we have to choose which factor is the most important. For example, a metal item might need to be very light and strong. Titanium is perfect for this, but using titanium is extremely expensive, so we use aluminum instead