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Physics 1 > P1 Part A > Flashcards

P1 Part A Flashcards

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1
Q

What are the features of particles in a solid?

A
  • Strong forces of attraction hold particles together
  • Fixed, regular arrangement
  • Little energy
  • Can vibrate only in a fixed position
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2
Q

What are the features of particles in a liquid?

A
  • Weaker forces than in solids
  • Particles are close but can move and form irregular arrangements
  • They have more energy than solids
  • Are able to move in random directions at low speed
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3
Q

What are particles in a gas like?

A
  • There are almost no forces of attraction between particles
  • Much more energy than in solids or liquids
  • Free to travel in random directions at high speeds
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4
Q

What affect does heat have on particles in solids and liquids?

A

It increases the kinetic energy

Solids melt, liquids boil

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5
Q

By what three methods can heat be transferred?

A

Radiation, conduction or convection.

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6
Q

What are the features of infrared radiation?

A
  • Emitted by solids, liquids and gases.
  • It is continual and comes from the surface
  • The hotter the object, the more radiation
  • Dark, matte surfaces absorb and emit radiation well
  • Light, shiny surfaces reflect radiation
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7
Q

Why do vacuum flasks have a silver lining?

A

To maintain the temperature of whatever liquid they’re storing, the radiation of that liquid is reflected back into itself.

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8
Q

What sustainable method of heating water uses radiation and how?

A

Solar hot water panels contain black water pipes beneath a black surface. Radiation from the sun is absorbed and heats the water.

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9
Q

What is the main difference between conduction and convection?

A

Conduction mainly works with solids whereas convection is predominantly liquid/gas.

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10
Q

When does heat convection occur?

A

When more energetic particles move from the hotter region to the cooler region, transferring their heat energy between the two.

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11
Q

Give an example of technology that uses both conduction and convection, outline how it works

A

The immersion heater

  • Heat energy is transferred from the heater coils to the water by conduction.
  • The particles near the coils, gain energy, move faster and create more distance between themselves.
  • The density of the water is reduced and the hot water rises. Displacement occurs as the cold water sinks and becomes heated by the coils. This is known as convection current.
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12
Q

What is conduction?

A

The process whereby vibrating particles pass on their extra kinetic energy to neighbouring particles (as thermal energy).

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13
Q

Why are metals good conductors?

A

Because their electrons are free to move.

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14
Q

What is condensation?

A

The process by which a gas becomes liquid. As a gas cools, the particles lose kinetic energy and the attraction forces between them become stronger. When the gas is cool enough, condensation will take place.

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15
Q

What is evaporation and what are the two conditions necessary for it to happen?

A

It is when a liquid becomes a gas. Particles near the surface of a liquid can escape and become gas if:

  • They are travelling in the right direction
  • They have enough kinetic energy to overcome the attractive forces of the other particles in the liquid
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16
Q

Liquid particles only evaporate into a gas when it has reached its boiling point, true or false?

A

False. They can evaporate from temperatures much lower than the liquids boiling point.

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17
Q

Which particles in a liquid evaporate first and what overall effect does this have on the liquid?

A

The fastest moving particles with the most kinetic energy will evaporate first. This decreases the overall energy of the liquid and therefore causes a temperature decrease.

18
Q

Which biological process uses evaporation to cool you down?

A

Perspiration

19
Q

The rate of evaporation will be faster if the… (4)

A
  • Temperature is higher (more energy)
  • Density is lower (weaker attractive forces)
  • The surface area is larger (more particles near the surface)
  • Airflow over the liquid is greater
20
Q

The rate of condensation will be faster if the… (4)

A
  • Temperature of the gas is lower (less energy)
  • Airflow is less (concentration is higher)
  • The temperature of the surface the gas touches is lower
  • Density is higher (stronger attractive forces)
21
Q

Which two factors are the rate of heat transfer dependent on?

A

Surface area and volume

The type of material

22
Q

How does surface area effect the rate of heat transfer?

A

The bigger the surface area, the more infrared waves can be emitted/absorbed

23
Q

How does volume effect the rate of heat transfer?

A

The smaller the volume, the faster an object will cool because a higher proportion of the object is in contact with its surroundings.

24
Q

What will happen to heat transfer if an object is in contact with a good conductor?

A

It will be conducted away much more rapidly than if it is in contact with an insulator.

25
Q

List four features of a vacuum flask that limits heat transfer

A
  • Glass bottle is double walled with a vacuum in the middle
  • Walls either side of vacuum are silvered
  • The bottle is supported using insulating foam
  • The stopper is made of plastic and filled with cork or foam
26
Q

How are humans adapted to control heat (and maintain homeostasis)?

A
  • In the cold, hairs on skin stand up to trap a thick layer of insulating air, limits heat loss by convection.
  • If too warm, the body diverts more blood to nearer the surface of the skin so that more heat can be lost by radiation
27
Q

What is special about Arctic foxes and Desert foxes ears?

A

Arctic foxes have evolved small ears to reduce heat loss by radiation (smaller surface area).
Desert foxes have large ears to increase heat loss (larger surface area.

28
Q

What is the formula for calculating payback time?

A

Initial cost ÷ Annual saving

29
Q

List 5 methods of reducing heat loss in the home and what method of transfer it reduces

A
  • Draught proofing (convection)
  • Loft insulation (radiation)
  • Cavity wall insulation (convection, conduction and radiation)
  • Thick curtains (conduction and radiation)
  • Hot water tank jacket (conduction and radiation)
30
Q

What do U values signify?

A

How fast heat is transferred by a material.

The better the insulator, the lower the U value.

31
Q

What is specific heat capacity?

A

The measure of how much energy a substance can store

32
Q

What is the formula for calculating energy in relation to specific heat capacity?

Rearrange this to find the formula for SHC

A

Energy = Mass x Specific heat capacity x Temperature change

SHC = Energy ÷ (Mass x Temperature change)

33
Q

Why is water used in central heating systems? (2)

A
  • It has a high heat capacity

- It is liquid so can be easily pumped around pipes

34
Q

List the nine types of energy

A
  • Electrical
  • Sound
  • Kinetic
  • Light
  • Thermal
  • Nuclear
  • Chemical
  • Elastic Potential
  • Gravitational potential
35
Q

What is the principle of the conservation of energy and when is energy useful?

A

Energy can be transferred usefully from one form to another, it can be stored or dissipated but it can never be created or destroyed.

Energy is useful only when it can be converted from one form to another.

36
Q

What is the formula for working out energy efficiency - try and give both the energy and power examples?

A

Efficiency = Useful energy out ÷ Total energy in

Efficiency = Useful power out ÷ Total power in

37
Q

Give an example of when wasted heat energy can be turned into something useful

A

It’s transferred to the air thats used to warm the passenger compartment

38
Q

How do heat exchangers work?

A

A cold fluid is pumped through the wasted heat energy, the temperature of this liquid rises as it gains the heat energy. The heat from the liquid can be converted into a form of energy that’s useful and therefore less of the heat energy is ‘wasted’.

39
Q

What are the standard units for electrical energy and what formula is used to calculate it?

A

Kilowatt hours (kWh)

kWh = Power (in kW) x Time (in hours)

40
Q

How can you work out the cost of the number of kWh used?

A

Cost = kWh x Price per unit

41
Q

Why does a carpet feel warmer than concrete or lino?

A

Much like human hair, the fibres stand on end, trapping air particles and insulating their warmth.

Physics 1 (2 decks)

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