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Physics unit 1 > Kinetic Theory And Heat Transfer and efficiency > Flashcards

Kinetic Theory And Heat Transfer and efficiency Flashcards

1
Q

Describe a liquid in four points

A

Weak forces of attraction
Close together
Irregular arrangement
Move freely but slowly

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2
Q

Describe a gas in four points

A

Next to no forces of attraction
Far apart
Irregular arrangements
Move fast and randomly

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3
Q

Why do particles move faster in a substance with more heat

A

Because they have greater energy

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4
Q

Describe the basic definition of conduction

A

Vibrating particles passing on their excess kinetic energy to neighbouring particles

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5
Q

Conduction is faster in…

A

Dense solids

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6
Q

Why do dense solids increase the rate of conduction

A

Because the particles collide more

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7
Q

Insulators have….spaces between their particles

A

Large

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8
Q

Why are metals particularly good at conducting heat

A

Because they have delocalised electrons which collide with other electrons

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9
Q

Why do metals feel colder than other materials in cold weather

A

Because they are conducting away the heat at a faster rate

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10
Q

Define convection

A

More energetic particles move from the hotter area to the cooler area and take the energy with them

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11
Q

In a convection current what do the particles with the most energy do

A

Become less dense and rise

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12
Q

When the hotter particles ride what happens to the colder ones

A

They are displaced and therefore move downwards making them hotter and therefore less dense and heating up

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13
Q

Where is convection most effective

A

Round containers

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14
Q

When a gas cools down the particles…

A

Have less energy and move slower

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15
Q

The slower movement of particles leads to

A

The forces of attraction increasing meaning the particles get closer together and form a liquid (condense)

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16
Q

Describe a liquid in for points

A

Strong forces of attraction
Close together
Irregular arrangement
Move freely and slowly

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17
Q

Once the particles of a has have cooled as much a they are going to they turn into a

A

Liquid

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18
Q

What type of surface speeds up the process of condensation

A

A cold one

19
Q

Particles in a liquid evaporate when

A

They are moving in the right direction and with enough force to overcome the forces of attraction

20
Q

Why does evapoouration decrease the average temperature of a liquid

A

Because the hottest particles have escaped

21
Q

What process relies on evapouration to cool in the human body

A

Sweating

22
Q

Name four factors that increase the rate of evapouration

A

Higher temperature
Lower density
Greater surface area
Airflow is greater

23
Q

Why does a lower density increase the rate of evapouration

A

Because the forces of attraction are weaker

24
Q

Why does greater airflow increase the rate of evapouration

A

When water evaporates the air becomes a higher concentration water vapour which means less water will evaporate. Therefore if the airflow moved the concentrated air then the evapouration can continue at a faster rate

25
Q

The factors increasing the rate of condensation are…. to those increasing evapouration

A

Opposite

26
Q

What impact does the double walking of vacuum flask have in the cooling effect

A

It reduces conduction and convection

27
Q

What features means that less heat is lost to radiation in a vacuum flask

A

Shiny walls either side of the flask

28
Q

The stopper of a vaccum flask is made from what? Why?

A

Cork or foam to reduce the amount of energy lost through conduction and convection

29
Q

In excess heat more… Flows to the surface of the skin to increase the rate of…. Though…

A

Blood
Heat loss
Infrared radiation

30
Q

Are cost effectiveness and effectiveness the same

A

No

31
Q

Payback time=

A

Initial cost/annual saving

32
Q

The most effective methods of saving energy…

A

Save the most energy per year

33
Q

The most cost effective energy saving methods

A

Have the shortest payback time

34
Q

The better the insulator the … The U-value

A

Lower

35
Q

What does specific heat capacity measure

A

How much energy an object can store

36
Q

How is specific heat capacity measured

A

How much energy is required to increase the temperature of a 1kg substance by 1 degree

37
Q

What is the equation for specific heat capacity

A

Energy (j)=mass(kg) x specific heat capacity (j/kg/c) x temperature change

38
Q

The higher the specific heat capacity the more heat it

A

Can store

39
Q

Describe electrical energy

A

The flow of current

40
Q

Energy cannot be…

A

Created or destroyed only transferred

41
Q

The less energy wasted by a machine the more

A

Efficient

42
Q

Efficiency =

A

Useful energy out/total energy in (x100 for a percentage)

43
Q

How do u calculate the electricity ised from a Meter

A

You subtract the initial reading from the final reading

44
Q

Name the 3 factors when choosing an appliance

A

Energy usage
Initial cost
Running cost

Physics unit 1 (6 decks)

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