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yr 2 science eye > chapter 10 > Flashcards

chapter 10 Flashcards

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1
Q

SI unit for temperature

A

K, kelvin

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2
Q

heat is transferred from…

A

a hotter region to a cooler region

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3
Q

heat results in…

A
  • expansion
  • contraction
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4
Q

expansion in liquids (rising sea levels)

A
  • due to climate change and global warming, the oceans absorb more heat energy
  • expand and sea levels will rise
  • coastal erosion
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5
Q

expansion and contraction in gases (metal pipes)

A
  • metal pipes carrying steam are very flexible
  • can expand and contract safely without breaking
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6
Q

opening a jar

A
  • place cap of jar in hot water
  • metal lid expand more than glass jar
  • less tight and easier to unscrew
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7
Q

bimetallic strip

A

a strip made of 2 metals that expand at different rates

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8
Q

bimetallic strip example

A
  • brass (expand more)
  • steel (expand less)
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9
Q

bimetallic application

A
  • thermostats
  • bimetallic thermometers
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10
Q

thermomstats

A

help keep temperature of appliance constant

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11
Q

bimetallic strip in electric iron

A
  • turn the knob sets the temperature of iron at which is switches off
  • bimetallic strip in iron is strait and contacts are touching, forming a closed cicuit and allow electricity to flow through it
  • bimetallic strip expands when heated. brass expand more than steel, causing the strip to bend downwards, causing an open ciruit
  • this switches of the circuit
  • when the strip cools down, it becomes straight and the contacts touch again
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12
Q

bimetallic strip in thermometer

A
  • bimetallic strip is made into a coil, attached to a pointer
  • as temperature changes , the different expansion rates of the metals cause the coil to unwind (temp increase) or tighten (temp decrease)
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13
Q

hot air balloon

A
  • when air in hot air balloon is heated, the volume increase, while the mass stays the same
  • causes density to decrease, and the air to to rise
  • balloon floats
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14
Q

how can heat be transferred

A
  • conduction
  • convection
  • radiation
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15
Q

conduction definition

A

transfer of heat without the physical movement of the medium

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16
Q

states of matter conduction rates

A
  1. solid
  2. liquid
  3. gas
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17
Q

why is solid better conductor of heat

A
  • the particles are arranged closely to each other in an orderly matter.
  • when the particles gain energy, the transfer of the energy is more quick
18
Q

convection definition

A

the transfer of heat with the physical movement of the medium

19
Q

convection can be used for:

A

fluids (liquid and gas)

20
Q

convection in liquids

A
  • as the water at the bottom gain heat and expands, the density decreases, causing it to rise to the top, as seen with the purple colouring
  • cooler and denser water sinks to the bottom as it is more dense than the surrounding water at the top, as seen with purple colouring going downwards
  • hotter and less dense water rises, and cooler and more dense water sinks, forming a convection current.
  • after a while, the heat is evenly distributed, and the colour of the water is purple
21
Q

convection in gases

A
  • air above candle gains heat, expands, become less dense, and rises chimney A
  • cooler air plus smoke from paper move down chimney B into the container as it is less dense.
  • takes up space of the hotter air
  • gains heat and rises, forming a convection current
22
Q

radiation

A

transfer of heat from a hotter body to a cooler body without the need for a medium
- can take place in vaccum

23
Q

greenhouse effect

A

warming of the surface of earth
- heat is prevented from leaving earth by radiaiton
- greenhouse gases trap the heat

24
Q

factors affecting radiation

A
  • temperature of object
  • surface area of object
  • colour of object
  • texture of object
25
Q

factors affecting conduction

A
  • different materials
26
Q

temperature of object

A
  • hotter the body, the higher rate of radiation from the object
27
Q

surface area of object

A
  • higher the surface area, the higher the rate of radiation
28
Q

heat sink radiation

A
  • large surface area -> allows heat to be radiated from the appliance quickly
29
Q

absorption of radiation

A
  • dull, rough surfaces are better absorbers of heat the radiation
30
Q

emision of radiation

A
  • dull, rough surfaces are better emitters of radiation
31
Q

reflection of radiation

A
  • light/silver coloured surfaces can reflect radiation well
  • petrol: prevent them from heating up
32
Q

air condition convection

A

cold air released from the aircon is denser than the surrounding air, and will sink.

33
Q

heater convection

A

cool air near the heater gains heat, expands, becomes less dense and rises, causing cool air to replace the replacew the space taken up by the air previously

34
Q

sea breeze

A
  • clockwise
  • sun heats up land, which warms air above it, becoming less dense and rises.
  • air above the cooler sea replaces the air above the land
35
Q

land breeze

A
  • anti-clockwise
  • layer of air above sea is warmer, becoming less dense and rises
  • air above the cooler land moves to replace the air above the sea
36
Q

building and clothes radiation

A
  • things are painted white because they are poor absorbers of radiation from the sun
37
Q

clothing fins radiation

A
  • dull black to emit heat to surroundings
38
Q

kettles and pots radiation

A
  • silver and polished which is a poor emitor of heat, keeping contents warm
39
Q

emergency blanket

A
  • shiny surface: poor emitter of heat, will not emit heat form the body to surroundings
40
Q

solar collector

A
  • painted black to absorb most amount of radiation
  • heat running inside transferred from tubes to water by conduction
41
Q

vacuum flask (hot)

A
  • reduce heat loss by conduction
    -> insulated cap reduces rate of heat loss by conduction
  • reduce rate of heat loss by convection
    -> keeping cap screwed tightly prevents heat loss by convection
  • reduce rate of heat loss by conduction
    -> insulated support reduces rate of heat loss by conduction
  • prevent heat loss by conduction
    -> vacuum between walls prevent heat loss by conduction as it cannot occur in a vacuum
  • reduce rate of heat loss by radiation
    -> silvere lined walls reflect heat and reduce rate of heat loss by radiation
42
Q

THATS IT YAYAYAYA

A

Frickityfrackitydo

yr 2 science eye (12 decks)

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