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Year 8 Science > 8H Energy > Flashcards

8H Energy Flashcards

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1
Q

What is a Shadouf?

A

A type of lever used by ancient Egyptians

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2
Q

What is a machine?

A

Something that helps us to do work.

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3
Q

What can a force do to energy?

A

A force can transfer energy.

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4
Q

When is work done?

A

When a force is used to transfer energy.

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5
Q

What is the unit for energy?

A

Joules (J)

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6
Q

What 2 things affect work done?

A

Force applied and distance moved

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7
Q

What is displacement?

A

The shortest distance from a start to and end point.

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8
Q

What is the equation to calculate work done?

A

work done (J) = force (N) x distance (m)

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9
Q

How do machines make work easier?

A

They reduce the force needed to make something work.

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10
Q

Why isn’t a tractor a human powered machine?

A

They are powered using sources of energy other than us

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11
Q

Why do humans require the use of machines?

A

There is a limit to how much force we can supply.

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12
Q

Give an example of a common machine.

A

Door handle, toilet flush, tap, pedal bin

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13
Q

How does a lever reduce work?

A

It reduces force by increasing distance.

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14
Q

How does a screwdriver help to open a tin of paint?

A

The screwdriver increases the distance the force is acting over.

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15
Q

How do wheels reduce work done?

A

They reduce friction.

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16
Q

What machines are present in a bicycle?

A

Levers, gears and wheels.

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17
Q

What state of matter does conduction occur through?

A

Solids

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18
Q

How do particles in a solid move?

A

They vibrate in place

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19
Q

What is a thermal insulator?

A

Materials which are not good at allowing the transfer of energy through them.

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20
Q

Give an example of a thermal conductor.

A

Metals

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21
Q

Which states of matter does convection occur in?

A

Liquids and Gases (Fluids)

22
Q

What is a convection current?

A

A current in a fluid that allows the transfer of heat energy.

23
Q

What does radiation travel as?

A

A wave

24
Q

Describe the frequency of infrared radiation.

A

The frequency is lower than red light.

25
Q

Name three places where it is common to have insulation in our homes.

A

Cookers, fridges, walls, loft, etc.

26
Q

What is something called if energy passes through it at a slow rate.

A

Insulator

27
Q

In the experiment shown- what is the independent variable?

A

Material the rod is made from.

28
Q

In the experiment shown- what is the dependent variable?

A

Time taken for the pin to drop.

29
Q

In the experiment shown- name 1 control variable.

A

Length of the rod, placement of pin, time heat is applied.

30
Q

When insulating something, why should fluids not be allowed to flow?

A

Fluids can transfer energy through convection.

31
Q

What type of materials are good at reflecting waves?

A

Shiny objects.

32
Q

Why do builders put plastic foam between walls for insulation?

A

The foam contains air pockets- good insulator.

33
Q

Give an example of a use of a thermal conductor.

A

Saucepans, radiators,

34
Q

Give an example of a use of a thermal insulator.

A

Food containers, loft insulation.

35
Q

What is the independent variable in this experiment?

A

The insulation material.

36
Q

What is the dependent variable in this experiment?

A

Temperature change over time.

37
Q

Why is the experiment carried out on a heat-proof mat?

A

To minimise heat loss through the base of the can.

38
Q

What is the function of the lid?

A

To minimise heat loss through convection.

39
Q

Identify a control variable for the experiment.

A

Number of layers of insulation material, starting temperature, time the temperature was measured.

40
Q

How will you know which material is the best insulator?

A

The test where the temperature decreased the least.

41
Q

How will the type of material/ number of layers be represented on the graph?

A

Curves on the same axis

42
Q

Why do we need to draw a graph of our data?

A

To see any patterns in the data

43
Q

How can you easily measure thermal energy transfer?

A

Monitor temperature

44
Q

In what direction is thermal energy transferred?

A

From a warm object to a cooler object

45
Q

What is thermal equilibrium?

A

An equal temperature in all objects.

46
Q

What is a vacuum flask made from?

A

2 glass layers covered in a reflective surface.

47
Q

What is a vacuum?

A

An area with no particles.

48
Q

Why is a vacuum useful?

A

Thermal energy can not be transferred by conduction of convection through a vacuum.

49
Q

Why is the glass silvered?

A

To reflect the radiation.

50
Q

What is the function of the lid?

A

To stop heat loss through convection.

Year 8 Science (10 decks)

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