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science > year 2 chap 10 > Flashcards

year 2 chap 10 Flashcards

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1
Q

what is the SI unit of temperature?

A

Kelvin (K)

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2
Q

what is the SI unit for heat energy?

A

Joule (J)

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3
Q

heat is transferred from an object of ____ to an object of ____

A

higher temperature ; lower temperature

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4
Q

the temperature change continues until?

A

until the two objects reach the same temperature

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5
Q

what happens when a substance is heated?

A
  • it gains heat and expands
  • increases in volume
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6
Q

what happens when a substance is cooled?

A
  • it loses heat and contracts
  • decreases in volume
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7
Q

heat energy can also be known as?

A

thermal energy

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8
Q

what happens to the particles in a solid state when it is heated?

A
  • its particles will gain energy and vibrate more vigorously about their fixed positions
  • the distance between the particles increase, which cause the volume of the substance to increase
  • as a result, the substance expands
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9
Q

what happens to the particles in a solid state when it is cooled?

A
  • its particles will lose energy and vibrate less vigorously about their fixed positions
  • the distance between the particles decrease, which cause the volume of the substance to decrease
  • as a result, the substance contracts
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10
Q

do all particles in a solid still vibrate when it’s cold?

A

yes

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11
Q

what is the law of conservation of mass?

A

mass cannot be created nor destroyed

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12
Q

the number and size of particles in a substance ___ during expansion and contraction

A

remains the same

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13
Q

why are metal railways built with gaps in the tracks?

A
  • a metal railway track gains heat and expands when it’s hot
  • the track can buckle if it’s made in one continuous metal piece, which may cause the trains to derail.
  • thus, expansion gaps between railway tracks provide space for expansion
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14
Q

why do sea levels rise because of global warming?

A

climate change includes global warming and this results in oceans absorbing more heat energy, causing the oceans to expand

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15
Q

how can we apply thermal expansion and contraction to opening jars with metal lids?

A

we can place the lid in hot water to make the jar easier to open as the metal lid expands more than the glass jar

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16
Q

what is a bimetallic strip?

A

a bimetallic strip is made up of two metals that expand at different rates upon the same change in temperature

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17
Q

if a bimetallic strip was made up of brass on the upper layer and steel on the bottom layer, which way will the bimetallic strip curve when it’s heated? why?

A

it will curve downwards as the brass strip expands more than the steel strip

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18
Q

if a bimetallic strip was made up of brass on the upper layer and steel on the bottom layer, which way will the bimetallic strip curve when it’s cooled? why?

A

it will curve upwards as the brass strip contracts more than the steel strip

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19
Q

when an object is heated, its ___ increases

A

volume

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20
Q

when an object is heated, its ___ remains the same

A

mass

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21
Q

how to calculate density?

A

mass/volume

22
Q

why is it that when an object is heated, its density decreases?

A
  • density is mass/volume
  • as mass does not change and volume increases, density would decrease
23
Q

heated air ___ because?

A

heated air rises because it is less dense than the surrounding air

24
Q

what are the 3 ways that heat energy is transferred?

A
  1. conduction
  2. convection
  3. radiation
25
Q

how do particles (atoms and molecules) transfer energy to each other?

A
  • through collisions!
  • one molecule collides with another molecule and passes on KE
  • the molecule with greater KE passes energy to the molecule with less KE
26
Q

which materials are better conductors of heat?

A

metals such as iron and copper

27
Q

which materials are better insulators of heat?

A

wood, plastic and glass

28
Q

what is conduction?

A

conduction is the transfer of heat energy from one object to another object through direct touch

29
Q

how does conduction happen when a metal ladle is placed in a hot pot of soup?

A

heat energy is transferred from the heated end of the ladle, which is in contact w. the heat source, to the handle of the ladle, which is furthest from the heat source

30
Q

___ are generally better conductors of heat than ___

A

solids ; fluids (e.g liquids and gases)

31
Q

what are solids generally better conductors of heat than liquids and gases?

A

the particles in a solid are arranged closer to one another, which enables the transfer of heat energy to occur more quickly

32
Q

what is convection?

A

convection is the transfer of heat energy from one place to another by the physical movement of a medium (mainly liquids and gases)

33
Q

explain the coloured water in the beaker experiment

A
  1. the flame of the bunsen burner heats up the water at the bottom of the beaker
  2. as the heated water expands, its volume increases
  3. since the mass remains constant, the increase in volume results in a decrease in density. The hotter and less dense water moves to the top of the beaker
  4. the cooler and denser water in turn sinks to the bottom of the beaker
34
Q

land breeze and sea breeze, which on occurs during the day and which one occurs doing the night?

A
  • land breeze occurs during the night
  • sea breeze occurs during the day
35
Q

explain land breeze :)

A

at night, the air above the sea is warmer (it is less dense) so it rises
the cooler air above the land (which is denser) moves to replace the air above the sea and the cycle repeats.

36
Q

explain sea breeze :)

A

during the day, the sun heats up the land which warms the air above it (the heated up air is less dense) and it rises
the cooler air above the sea moves in to replace the air above the land and it repeats

37
Q

what is a difference between conduction and convection?

A
  • in conduction, thermal energy is transferred from one particle to another w/o any flow of the medium
  • in convection, thermal energy is transferred through the actual movement of particles in the medium due to differences in density
38
Q

why conduction and convection of thermal energy from the sun cannot take place in outer space?

A

space is vacuum so there are no particles for conduction and convection to take place

39
Q

what is radiation?

A

radiation is the transfer of energy from a hotter body to a cooler body without the need for a medium

40
Q

heat energy is transferred from the sun to the Earth by ___

A

radiation

41
Q

heat energy that is transferred by radiation may be ___

A

absorbed or reflected

42
Q

what are the factors affecting the rate of conduction?

A

type of material as different materials conduct heat at different times

43
Q

what are the factors affecting the rate of radiation?

A

temperature of object
surface area of object
type (texture and colour) of surface

44
Q

how does the temperature of an object affect its rate of radiation?

A

the hotter the body of an object, the higher the rate of radiation from the object

45
Q

how does surface area of an object affect its rate of radiation?

A

objects with a larger surface area has a higher rate of radiation

46
Q

how does the type (texture and colour) of surface affect the absorption of radiation?

A
  • black surfaces are better absorbers of radiation than white surfaces
  • dull, rough surfaces are also better absorbers of radiation than smooth, shiny surfaces
47
Q

how does the type (texture and colour) of surface affect the emmission of radiation?

A
  • black surfaces are better emitters of radiation than white surfaces
  • dull, rough surfaces are also better emitters of radiation than smooth, shiny surfaces
48
Q

give me an example of conduction used in our daily lives

A

the metal base of a pan is a good conductor of heat so that heat energy can be transferred quickly from the heat source to the food

49
Q

give me an example of convection used in our daily lives

A

air-cons are usually placed at the top of the room as warm air (less dense) rises and collects under the ceiling, the air-con cools the warm air (and it becomes more dense) and it sinks to the bottom of the room and the cycle repeats

50
Q

give me an example of radiation used in our daily lives

A

cooling fins found at the back of fridges are usually dull black as they emit heat easily to the surroundings to keep the fridge cool

51
Q

explain how a vacuum flask works to reduce the transfer of heat energy through conduction, convection and radiation

A
  • the insulated cap reduces the the rate of heat loss by conduction
  • keeping the cap tightly screwed reduces the rate of heat loss by convection
  • the vacuum between the glass walls prevents heat loss by conduction as it cannot happen in a vacuum.
  • the silver walls reflect heat and reduce the rate of heat loss by radiation
  • the insulated support at the bottom of the flask reduces the rate of heat loss bo conduction

science (8 decks)

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