Thermal Physics Flashcards
1
Q
Describe particle motion in solids.
A
vibration about a fixed position
2
Q
Can solids be compressed?
A
no
3
Q
Do solids have a fixed shape?
A
yes
4
Q
Do solids have a fixed volume?
A
yes
5
Q
How are the forces of attraction/bonds between molecules in a solid?
A
strong
6
Q
How are molecules arranged in solids?
A
regular arrangement, molecules close together, tightly packed
7
Q
Describe particle motion in liquids.
A
Particles flow and move over each other
8
Q
Can liquids be compressed?
A
no
9
Q
Do liquids have a fixed shape?
A
no
10
Q
Do liquids have a fixed volume?
A
yes
11
Q
How are the forces of attraction/bonds between molecules in a liquid?
A
weaker than in a solid
12
Q
How are molecules arranged in liquids?
A
molecules are close together, irregular arrangement
13
Q
Describe particle motion in gases, and the shape they take.
A
molecules are free to move, move randomly, all directions
take shape of container
14
Q
Can gases be compressed?
A
yes
15
Q
Do gases have a fixed shape?
A
no
16
Q
Do gases have a fixed volume?
A
no
17
Q
How are the forces of attraction/bonds between molecules in a gas?
A
weak forces of attraction, molecules far apart
18
Q
What is internal energy?
A
energy of the molecules of a body
19
Q
What is kinetic energy?
A
energy due to molecule movement
20
Q
What is potential energy?
A
energy due to forces and separation of molecules
21
Q
The greater the ______ of the molecules, the greater the potential energy
A
separation
22
Q
In potential energy, what is the type of force?
A
electrical
23
Q
solid -> liquid
A
melting
24
Q
gas -> liquid
A
condensation
25
liquid -> solid
solidification
for water, freezing
26
liquid -> gas
boiling or evaporation
27
In order to weaken/break bonds between molecules, what do melting and boiling do?
absorb heat energy
28
Which processes absorb heat energy? Why?
melting and boiling
to weaken and break bonds between molecules and increase molecule separation
29
What happens as temperature increases, to particles?
they move faster
30
What is the lowest possible temperature (absolute 0)?
-273 celcius degrees
31
What does it mean to the particles if an object is at absolute 0?
particles have the least kinetic energy
- temperature at which particles in a gas exert no pressure and are no longer moving, hence not colliding with their container
32
Describe the pressure of a gas, relation to motion of its particles and their collisions with a surface.
moving gas molecules collide with a surface, exerting a force.
33
What is the effect of temperature on gas pressure? Why?
since molecules will move more quickly, they will collide with the walls of the container/surfaces more often, exerting a greater pressure
positive correlation
34
What is one piece of evidence for the kinetic particle model of matter?
random movement of particles in suspension
35
Describe Brownian motion.
Brownian motion is the random collision between particles in suspension and the particles of the gas/liquid
36
What causes pressure in gases?
force exerted when a particle collides with surfaces (creates F/a)
37
What is Boyle's law?
For a fixed mass of gas at constant temperature, pressure is inversely proportional to volume
38
What happens to the pressure of a gas as volume increases, at constant temperature?
decreases
39
Why is pressure higher when volumes are smaller?
molecules collide off walls of the container more often.
40
What is the formula to find out pressure and volume before and after?
P1V1=P2V2
41
What happens to the pressure of a gas when temperature changes (volume constant)?
pressure increases as temperature increases
42
Why is pressure higher at higher temperatures?
molecules move faster and collide with container walls more often.
43
What is the equation relating degrees K and C?
T (in K) = 0 (in C) + 273
44
Which processes emit heat energy? Why?
solidification and condensation, to strengthen or make molecular bonds and decrease molecule separation
45
What is temperature, in terms of molecules?
measure of the average kinetic energy of the molecules of a substance
46
How is the graph for P x V = constant?
linear, from origin
47
For a fixed mass of gas at constant temperature, what is the relationship between pressure and volume?
P x V = constant
48
What happens when a material receives heat energy, in terms of expansion?
molecules move faster, molecules separate further. the material will expand
49
What happens when a material loses heat energy, in terms of expansion?
molecules move slower, molecules come close together. the material will contract
50
Which state of matter expands most, for the same amount of heat energy?
Why?
gases, no forces of attraction between molecules, molecules have enough energy to overcome the weak intermolecular forces
51
Which state of matter expands the least, for the same amount of heat energy?
Why?
solid, because the molecules cannot overcome the strong intermolecular forces holding the molecules together
52
If a gas and a solid are subject to the same amount of heat energy, which will expand more?
gas
53
What are 3 applications of thermal expansion in everyday life?
gaps in railway tracks
fitting metal tyres onto railway train wheels
bimetallic strips
thermometers
54
Why are there gaps in railway tracks?
because it leaves space for solids to expand into when temperature increases
55
How is thermal expansion used to fit metal tyres onto railway train wheels?
since the wheel is bigger than the tyre, the tyre is heated so it expands. this will make it possible for it to fit over the wheel. then it is cooled to contract.
56
How does a bimetallic strip work?
two different materials on either side of a strip. when it is heated, the material which expands more will expand and cause the strip to bend (vice verse for cooling)
57
What is the relative order of magnitudes of the expansion of solids, liquids and gases?
(least expansion) solid - liquid - gas (most expansion)
58
What causes an increase in internal energy?
rise in temperature of an object
59
In terms of molecules, what does an increase in temperature mean?
increased average kinetic energy of molecules of a substance
60
Define the term 'specific heat capacity'.
the heat energy needed for a body of mass given to increase its temperature (by 1 degree)
61
What is the equation for specific heat capacity?
c= ∆E / m∆θ
62
Describe an experiment to find out the s.h.c of water.
1. connect a power pack to an ammeter, voltmeter and an electric heater
2. measure starting temperature and mass of water (which should be in calormeter cup, with insulating air and another metal cup)
3. turn heater on and measure the current and voltage
4. turn heater off after 5 min, wait and measure maximum temperature
5. find the find energy using the H = VIt formula
6. plug results in s.h.c formula
63
How do thermometers use thermal expansion?
mercury expands as the temperature increases
64
What happens to the temperature of a substance as it goes from a solid to a liquid?
it will increase until the melting point is reached. the temperature stays constant until the substance is a liquid.
65
What happens to the temperature of a substance as it goes from a liquid to a gas?
it will increase until the boiling point is reached. temperature stays constant until the substance is a gas.
66
Name 3 differences between boiling and evaporation.
boiling only occurs at boiling point
evaporation is much slower
evaporation is only at the surface, unlike boiling which is throughout surface
boiling forms bubbles
boiling requires an external thermal energy source
67
What is condensation, in terms of particles?
when a gas cools down, the particles move more slowly
they do not have the energy they had to overcome the intermolecular forces
particles get closer together and form a liquid
68
What is solidification, in terms of particles?
when a liquid cools down, the particles move more slowly
they do not have the energy they had to overcome the intermolecular forces
particles get closer together and form a solid
69
Define 'evaporation'.
the escape of more energetic particles from the surface of a liquid
70
Evaporation has a ______ effect.
cooling
71
How does evaporation cool down a liquid?
molecules with a higher KE escape, leaving behind molecules with less KE. this causes the liquid to cool down.
72
What is one example of evaporation's cooling effect in real life?
sweating
73
How does sweating work?
water evaporates from our skin, the temperature of the water falls, and removes heat energy from our body
74
What are factors that influence the rate of evaporation?
temperature
wind
surface area
75
How does temperature influence the rate of evaporation?
molecules move faster, can escape surface of liquid
increased temperature, increased rate of evaporation
76
How does wind influence the rate of evaporation?
decreases number of molecules above the liquid surface, leaving space for them
increased wind, increased rate of evaporation
77
How does surface area influence the rate of evaporation?
more molecules are positioned at the surface and can escape
increased surface area, increased rate of evaporation
78
How is heat transferred in solids (conduction)?
the particles which vibrate about a fixed spot gain energy, colliding with the particles next to them and transferring thermal energy
79
Define 'conduction'
Where does it occur?
transfer of thermal energy from one object to another. occurs in solids
80
Why are metals good thermal and electric conductors?
their delocalised electrons can move throughout the metal
81
How does conduction occur via delocalised electrons?
electrons gain ke from hot end of metal, moving and colliding with atoms, increasing their KE and temp.
82
Why are gases poor thermal conductors?
the particles are far apart, making it hard for energy to be transferred from one particle to another
83
why are liquids and gases poor conductors
particles are too far from each other and rarely make contact to transfer energy
84
What is one experiment to test conductivity?
put boiling water in a box with holes
place rods of different materials in these holes
place drawing pins held with petroleum jelly on the far ends of rods
see which drawing pins fall of first due to conduction of heat from water
85
Define 'convection'
method of thermal energy transfer in liquids and gases
86
How does convection work in liquids/gases? What is the name given to this movement?
hot fluid expands, becomes less dense and rises
cold fluid sinks as it is more dense
the colder fluid is then heated and rises again, forming a convection current
87
What is a convection current?
movement of fluid that transfers heat energy upwards
88
Describe one experiment to test convection
fill a beaker with water, then place a potassium manganate crystal into the beaker
place a bunsen burned flame right under the crystal
you will see the convection from the movement of color in the beaker
89
Define 'radiation'
heat transfer from a hot to a colder place by infrared electromagnetic waves
90
Which object emit thermal/infrared radiation?
all of them :)
91
Does infrared radiation require a medium?
no, like all electromagnetic waves
92
Which colours and textures are good emitters and absorbers of heat energy?
dark colours (black)
dull textures
93
Which colours are poor emitters and absorbers of heat energy?
white/shiny colours
94
Which colours are good reflectors of heat energy?
white/shiny colours
95
In terms of energy, what is necessary for an object to be at a constant temperature?
transfer energy away from object at same rate that it receives energy
96
How does the Earth's average temperature remain constant?
infrared radiation energy per second absorbed from sun is balanced by i.r energy per second emitted to space
97
What is one experiment to test good/bad emission of infrared radiation?
place two metal cans (one silver, one matte black) with hot water, a thermometer and a lid on them
observe that the black one cools down faster since they emit better
98
What is one experiment to test good/bad absorption of infrared radiation?
take two metal cans (one matte black, one silver) with water, a thermometer and a lid on them
place them equidistantly from an electric radiant heater
black will heat up faster since it absorbs heat better
99
What are two factors affecting rate of emission of radiation?
- surface temperature
- surface area
100
The hotter an object is, the ____ infrared radiation it emits.
more
101
A bigger object (larger s.a) emits ____ radiation than a smaller object (ignoring other factors)
more
102
objects with _____ surface areas will absorb more radiation than those with ______ surface areas.
large
small
103
applications/consequences of thermal expansion
- metal railway track expand and start to curve (buckling)
- buckling of road surfaces
- buckling of bridges
104
expansion of solids
- expand slightly
- low energy molecules overcome th strong intermolecular force
105
expansion in liquids
- expand more than solids
- molecules have enough energy to partially overcome the intermolecular force
106
expansion in gases
- expand the most
- molecules have high energy to overcome the intermolecular force
107
what is internal energy
total energy stored in a system by the particles that make up the system due to their motion and positions
108
what is specific heat capacity
Energy required to change the temperature of 1 kg of the substance by 1 °C.
109
evaporation
- occurs to any liquid at any temp and results in the cooling of the liquid
- molecules that hit the surface provide energy
110
melting and boiling point of water
0 and 100
111
boiling
- occurs to a liquid at certain temp and involves temperature input
- does not result in cooling of the liquid
