advanced information Flashcards
1
Q
What are the 8 energy stores?
A
- Thermal (or internal) energy
- Kinetic energy
- Gravitational potential energy
- Elastic potential energy
- Chemical energy
- Magnetic energy
- Electrostatic energy
- Nuclear energy
2
Q
What are the 4 ways energy can be transferred?
A
Mechanically (by a force doing work) Electrically (work done by moving charges) By heating By radiation (e.g. Light or sound)
3
Q
What is a system?
A
A system is a single object (e.g. The air in a piston) or a group of objects (e.g. Two colliding vehicles) that you’re interested in
4
Q
What is a closed system?
A
Systems where neither matter nor energy can enter or leave
5
Q
What happens when a system changes?
A
Energy is transferred
6
Q
What is the conservation of energy principle?
A
Energy is always conserved: it can be transferred usefully, stored or dissipated, but can never be created or destroyed
7
Q
What is power?
A
The rate of energy transfer, or the rate of doing work
8
Q
What is power measured in?
A
Watts
9
Q
What is one watt equivalent to?
A
1 joule of energy transferred per second
10
Q
What are the two equations to calculate power?
A
P = E/t (power = energy transferred / time) P = W/t (power = work done / time)
11
Q
what is a powerful machine?
A
one that transfers a lot of energy in a short space of time
12
Q
what is a method of reducing frictional forces?
A
lubrication
13
Q
what is thermal conductivity?
A
a measure of how quickly energy is transferred through a material by particles colliding with each other
14
Q
what is the most common store that waste energy is transported to?
A
thermal energy store
15
Q
what is another name for internal energy?
A
thermal energy
16
Q
what is always the net change in the total energy of a closed system?
A
0
17
Q
what is work done the same as?
A
energy transferred
18
Q
give two ways that work can be done
A
- when current flows
2. by a force moving an object
19
Q
describe the changes in energy stores when a ball is thrown into the air?
A
the initial force exerted by a person to throw a ball upwards does work. It causes an energy transfer from the chemical energy store of the person’s arm to the kinetic energy store of the ball and arm
20
Q
describe the changes in energy stores when a ball is dropped from a height?
A
a ball dropped from a height is accelerated by gravity. The gravitational force does work. It causes energy to be transferred from the ball’s gravitational potential energy store to its kinetic energy store
21
Q
describe the changes in energy stores when a ball is dropped from a height?
A
a ball dropped from a height is accelerated by gravity. The gravitational force does work. It causes energy to be transferred from the ball’s gravitational potential energy store to its kinetic energy store
22
Q
describe the energy transfers that occur when the wind causes a windmill to spin
A
energy is transferred mechanically [1 mark] from the kinetic energy store of the wind [1 mark] to the kinetic energy store of the windmill [1 mark]
23
Q
what does the amount of energy in an object’s kinetic energy store depend on?
A
the object’s mass and speed
24
Q
what is the formula for kinetic energy? give the units for everything
A
Ek = 0.5 x m x v^2 kinetic energy (J) = 0.5 x mass (kg) x velocity^2 (m/s)
25
what does the amount of energy in a gravitational potential energy store depend on?
the object's mass, its height and the strength of the gravitational field the object is in
26
what is the equation for gravitational potential energy (g.p.e)? give the units for everything
Ep = mgh
| g.p.e (J) = Mass (kg) x gravitational field strength (N/kg) x height (m)
27
for a falling object when there's no air resistance, what is the relationship between the energy lost from the g.p.e store and the energy gained in the kinetic energy store? how does this change if there is air resistance?
when there is no air resistance, they are equal. However, in real life, air resistance acts against all falling objects - it causes some energy to be transferred to other energy stores, e.g. the thermal energy stores of the object and surroundings
28
how can energy be transferred to an object's elastic potential energy store?
stretching or squashing an object can transfer energy to its elastic potential energy store
29
what is the equation for elastic potential energy? Give the units for everything
Ee = 0.5 x k x e^2
| elastic potential energy (J) = 0.5 x spring constant (N/m) x extension (m)^2
30
what are the units for gravitational field strength?
N/kg
31
when can the equation for elastic potential energy not be used?
after the limit of proportionality has been exceeded
32
what is specific heat capacity?
the amount of energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius
33
give the equation that links energy transferred and specific head capacity, including units
change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change (°C)
34
what are the units for specific heat capacity?
J/kg°C
35
describe an investigation to find the specific heat capacity of a material
1. set up a circuit that connects an ammeter and a heating element in series
2. to investigate a solid material (e.g. copper), you'll need a block of the material with two holes in it (for the heater and thermometer to go into)
3. measure the mass of the block, then wrap it in an insulating layer (e.g. a thick layer of newspaper) to reduce the energy transferred from the block to the surroundings. Place the thermometer into the smaller hole and the heater into the larger one
4. measure the initial temperature of the block and set the potential difference, V, of the power supply to be 10 V. Turn on the power supply and start a stop watch
5. as the heater starts to heat the block up, take readings of the temperature and current, I, every minute for 10 minutes. You should find that the current through the circuit doesn't change as the block heats up.
6. when you've collected enough readings (10 should be enough), turn off the power supply. Using your measurement of the current, and the potential difference of the power supply, you can calculate the power supplied to the heater, using P = VI. You can use this to calculate how much energy, E, has been transferred to the heater at the time of each temperature reading using the formula E = Pt, where t is time in seconds since the experiment began
7. if you assume all the energy supplied to the heater has been transferred to the block, you can plot a graph of energy transferred to the thermal energy store of the block against temperature
8. find the gradient of the graph. This is (change in temperature)/(change in energy). Using the equation for specific heat capacity, you can determine that the shc of the material of the block is 1/(gradient x the mass of the block)
9. you can repeat this experiment with different materials to see how their specific heat capacities compare
36
how can the investigation to determine the specific heat capacity of a material be adjusted to work with liquids?
place the heater and thermometer in an insulated beaker filled with a known mass of the liquid.
37
what is power?
the rate of energy transfer, or the rate of doing work
38
what is power measured in? What does one of these measurements equal?
power is measured in watts. One watt = 1 joule of energy transferred per second
39
give 2 equations to calculate power
1. Power (W) = Energy transferred (J) / time (s)
(P = E/t)
2. Power (W) = Work done (J) / time(s)
(P = W/t)
40
what is a powerful machine?
a machine that transfers a lot of energy in a short space of time
41
how is energy transferred in a kettle?
kettles transfer energy electrically from the mains ac supply to the thermal energy store of the heating element inside the kettle
42
how is energy transferred in a handheld fan?
Energy is transferred electrically from the battery of a handheld fan to the kinetic energy store of the fan's motor
43
with a higher current is more or less energy transferred to the thermal energy stores of the components (and then the surroundings)?
more
44
what does the total energy transferred by an appliance depend on?
how long the appliance is on for and its power
45
what is the power of an appliance?
the energy that it transfers per second
46
what is a power rating? what does it tell you?
appliances are often given a power rating - they're labelled with the maximum safe power that an appliance can operate at. You can usually take this to be their maximum operating power. The power rating tells you the maximum amount of energy transferred between stores per second when the appliance is in use
47
how does the power rating help customers choose between models?
the lower the power rating the less electricity an appliance uses in a given time and so the cheaper it is to run.
However, a higher power doesn't necessarily mean that it transfers more energy usefully. An appliance may be more powerful than another, but less efficient, meaning that it may only transfer the same amount of energy (or even less) to useful stores.
48
what is energy transferred per charge passed?
potential difference
49
what happens when an electrical charge goes through a change in potential difference?
energy is transferred
50
what is the national grid?
a giant system of cables and transformers that covers the UK and connects power stations to consumers
51
what are some events that could cause the demand for electricity to increase?
demand increases when people get up in the morning, come home from school or work, and when it starts to get dark or cold outside. popular events like a sporting final being shown on TV could also cause a peak in demand.
52
what are some measures power stations have in place to cope with an unexpectedly high demand?
power stations often run well below their maximum power output, so there's spare capacity to cope with a high demand, even if there is an unexpected shut down of another station. Lots of smaller power stations that can start up quickly are also kept on standby, just in case
53
does the national grid use a high or low potential difference? what about current?
it uses a high pd and a low current
54
why does the national grid use a high potential difference and a low current?
to transmit the huge amount of power needed, you need either a high potential difference or a high current (P=VI). A higher current would mean losing a lot of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings, so it's much cheaper to boost the potential difference up really high and keep the current as low as possible. This makes the national grid an efficient way of transferring energy.
55
what is the potential difference in the wires of the national grid?
400,000 volts
56
what is used in the national grid to get the voltage up to 400,000 volts?
step-up transformers (and big pylons with huge insulation)
57
what do all transformers have?
two coils, a primary coil and a secondary coil, joined with an iron core
58
how do step-up transformers work?
step-up transformers have more turns on the secondary coil than the primary coil. As the pd is increased by the transformer, the current is decreased
59
do step down transformers have more turns on the primary or secondary coil?
primary
60
what is the equation linking the pd and current of both the coils in a transformer? Why is this?
pd across primary coil (V) x current in primary coil (A) = pd across secondary coil (V) x current in secondary coil (A)
VpIp = VsIs
this is because transformers are nearly 100% efficient, so the power in primary coil = power in secondary coil
61
how efficient are transformers?
nearly 100%
62
is the power in the primary coil greater than, equal to or less than the power in the secondary coil?
equal to
63
why does a moving charge transfer energy?
the charge does work against the resistance of the circuit (work done is the same as energy transferred)
64
what are electrical appliances designed to do?
electrical appliances transfer energy between stores electrically - they are designed to transfer energy to components in the circuit when a current flows
65
give the equation to work out the amount of energy transferred by electrical work
```
energy transferred (J) = Power (W) x Time (s)
(E = Pt)
```
66
how does a power source work?
energy is supplied to the charge at the power source to 'raise' it through a potential. The charge then gives up this energy when it 'falls' through any potential drop in components elsewhere in the circuit. A battery with a bigger pd will supply more energy to the circuit which flows round it, because the charge is raised up 'higher' at the start
67
what is the equation to work out energy transferred using charge flow and potential difference?
```
Energy transferred (J) = charge flow (C) x potential difference (V)
(E = QV)
```
68
give the formula to find power using potential difference and current. Include units
Power (W) = Potential difference (V) x Current (A)
| P = VI
69
give the equation to find power using current and resistance
power (W) = current (A)^2 x resistance (ohms)
| P = I^2 x R
70
how is electricity distributed around the UK?
through the national grid
71
what does the national grid do?
the national grid transfers electrical power from power stations anywhere on the grid (the supply) to anywhere else on the grid where it's needed (the demand) - e.g. homes and industry
72
what are step-down transformers used for?
to increase the current and decrease the potential difference of electricity transferred over the national grid in order to make it safe for the local consumer
73
how can you view the particles that make up matter in particle theory?
as tiny balls
74
what is different in the particles of a substance in each state?
the arrangement and energy of the particles
75
describe solids
strong forces of attraction hold the particles close together in a fixed, regular arrangement. The particles don't have much energy so they can only vibrate around their fixed positions
76
describe liquids
there are weaker forces of attraction between the particles. The particles are close together, but can move past each other, and form irregular arrangements. They have more energy than the particles in a solid - they move in random directions at low speeds.
77
describe gases
There are almost no forces of attraction between the particles. The particles have more energy than in liquids and solids - they're free to move, and are constantly moving with random directions and speeds
78
what creates pressure?
colliding gas particles
79
what is pressure?
when particles in a gas collide with something (like the walls of a container) they exert a force on it. Pressure is the force exerted per unit area.
80
how can increasing the temperature of a gas increase pressure?
when you heat up a gas you transfer energy to the kinetic energy stores of its particles. The temperature of a gas is related to the average energy in the kinetic energy stores of the particles in the gas. The higher the temperature, the higher the average energy. So as you increase the temperature of a gas, the average speed of its particles increases. This is because the energy in the particles' kinetic energy stores is 0.5mv^2. This means that, for a gas at a constant volume, increasing its temperature increases its pressure as the particles are travelling quicker, so it means they hit the sides of the container more often in a given amount of time. Each particle also has a larger momentum with means that they exert a larger force when they collide with the container.
81
what are the units of density?
kg/m^3 or g/cm^3
82
how many kg/m^3 are there in 1 g/cm^3?
1g/cm^3 = 1000kg/m^3
83
what is the equation for density?
density = mass / volume
84
what is the symbol for density?
the greek letter rho, which looks like a p
85
put the states of matter in order of increasing density
gas, liquid, solid
86
how do you find the density of a regular solid?
use a balance to find the mass of the object, and then measure its length, width and height with a ruler. calculate the volume with the relevant formula for that shape, and then use the equation density = mass / volume to find the density
87
how do you find the density of an irregular solid?
use a balance to measure the mass of the object, then find the volume by submerging it in a displacement can filled with water. The water displaced by the object will be transferred to the measuring cylinder. Record the volume of the water in the measuring cylinder - this is the volume of the object. Then use the formula density = mass / volume to find the density
88
how do you find the density of a liquid?
Place a measuring cylinder on a balance and zero the balance. Pour 10ml of the liquid into the measuring cylinder and record the liquid's mass. Pour another 10ml into the measuring cylinder, repeating the process until the cylinder is full, recording the total volume and mass each time. For each measurement use the formula density = mass / volume to find the density (1ml = 1cm^3), and then take an average of your calculated densities. This will give you a value for the density of the liquid
89
what is it called to go directly from a solid to a gas?
sublimination
90
is a change of state a chemical or physical change? What does this mean?
physical - this means you don't end up with a new substance - it's' the same substance you started with, just in a different form. If you reverse a change of state (e.g. freeze a substance that has been melted), the substance will return to its original form and get back its original properties
91
is mass conserved in a change of state?
yes
92
in a sealed container, what is the outward gas pressure?
the total force exerted by all of the particles in the gas on a unit area of the container walls
93
give two things the particle model can be used to explain
1. the different states of matter
| 2. differences in density
94
what does the density of an object depend on?
what it's made of and how its particles are arranged
95
who came up with the plum pudding model?
JJ thomson
96
describe the plum pudding model of the atom
a sphere of positive charge with negative electrons embedded in it.
97
what was the "alpha scattering experiment"?
Rutherford fired a beam of alpha particles at a thin sheet of gold foil
98
what did rutherford expect to happen in the alpha scattering experiment?
From the plum pudding model, he expected that the alpha particles would pass straight through or be very slightly deflected
99
what was the result of the alpha scattering experiment, and why did it contradict the plum pudding model?
Most of the alpha particles did pass straight through, but some were deflected more than expected and a few were deflected back the way they had come. This could not be explained by the plum pudding model, as there was no concentrated centre of mass that would deflect only some of the particles back
100
what was concluded from the alpha scattering experiment?
Because a few alpha particles were deflected back, they realised that most of the mass of the atom must be concentrated at the centre in a tiny nucleus. this nucleus must also have a positive charge, since it repelled the positive alpha particles. they also realised that because nearly all the alpha particles passed straight through, most of an atom is just empty space. this was the first nuclear model of the atom.
101
what changes did Niels Bohr make to the nuclear model of the atom?
he said that the electrons orbiting the nucleus do so at certain distances called energy levels (he came up with the idea of shells around the nucleus). His theoretical calculations agreed with experimental data.
102
who proved the existence of the neutron, and when? What did this explain?
James Chadwick in 1932. This explained the imbalance between the atomic and mass numbers
103
what is the radius of an atom?
about 1 × 10 to the power of -10 m
104
if electrons gain energy by absorbing EM radiation, do they move to a lower or higher energy level?
higher energy level, further from the nucleus
105
if electrons release EM radiation, do they move to a lower or higher energy level?
lower energy level, closer to the nucleus
106
what are isotopes?
different forms of the same element - they have the same number of protons but a different number of neutrons
107
what is radioactive decay? Why does it happen?
unstable elements decaying into other more stable elements, and giving out radiation as they do so. It happens because all elements have different isotopes, but there are usually only one or two stable ones. The other unstable isotopes tend to decay into other elements and give out radiation as the try to become more stable (they try to balance the number of protons and neutrons in their nucleus to get rid of any excess energy.
108
what type of radiation are helium nuclei?
alpha particles
109
what are alpha particles made up of?
two protons and two neutrons (like a helium nucleus)
110
what is alpha radiation's range in air?
a few cm - less than ten
111
what is alpha radiation stopped by?
a sheet of paper
112
how ionising are alpha particles?
very strongly
113
what are beta particles?
high speed electrons released by the nucleus. Beta particles have virtually no mass and a charge of -1
114
how ionising is beta radiation?
moderately
115
what is beta radiation's range in air?
a few metres
116
what is beta radiation stopped by?
a sheet of aluminium (around 5mm)
117
what are gamma rays?
Electromagnetic waves with a short wavelength
118
what is gamma radiation's range in air?
very far - kilometres
119
what is gamma radiation stopped by?
a thick sheet of lead or metres of concrete
120
when an atom emits an alpha particle, what does the mass number decrease by?
4
121
when an atom emits an alpha particle, what does the atomic number decrease by?
2
122
what is an alpha particle written as in atomic equations?
4
He (a helium nucleus)
2
123
when an atom emits a beta particle, what does the atomic number change by?
+1
124
when an atom emits a beta particle, what happens to the mass number?
it stays the same
125
what is a beta particle written as in atomic equations?
0
_ e (an electron)
-1
126
do gamma rays change the charge or the mass of the nucleus?
no
127
radioactive decay is random. true or false?
true
128
what is the half-life of a radioactive substance?
the time it takes for the number of radioactive nuclei in an isotope/sample to halve (it can also be described as the time taken for the activity (and so count rate) to fall to half of its initial value)
129
what is "activity" in radioactive samples?
the rate at which a source decays - the amount of decays per second
130
what is activity measured in?
Becquerels, Bq (where 1 Bq = 1 decay per second)
131
what happens to the radioactivity of a source over time?
it decreases - older sources emit less radiation
132
why do we use half-life as a measurement?
the activity never reaches zero, but half-life allows us to measure how quickly the activity drops off.
133
why is radiation dangerous?
ionising radiation can enter living cells and ionise atoms within them. This can damage the cells (which can cause things like cancer) or kill them off completely.
134
what is irradiation?
exposure to radiation (objects near a radioactive source are irradiated by it)
135
what is contamination? (in the context of radioactivity)
radioactive particles getting onto or into objects
136
what are some precautions to take in order to avoid contamination?
gloves and tongues should be used when handling sources, and some industrial workers wear protective suits to stop them breathing in particles
137
approximately, how big is the radius of an atom?
1 x 10^-10 metres
138
who was the first person to come up with the idea of an atom? What did their model look like?
a Greek man called Democritus first came up with the idea of an atom in the 5th century BC. He thought that all matter, whatever it was, was made up of identical lumps called "atomos". This view wasn't widely challenged until the 1800s
139
what changes did John Dalton make to the model of the atom?
In 1804 John Dalton agreed with Democritus that matter was made up of tiny spheres ("atoms") that couldn't be broken up, but he thought that each element was made up of a different type of "atom"
140
what lead Thomson to creating the plum pudding model of the atom?
He discovered particles called electrons that could be removed from atoms.
141
describe the nuclear model of the atom that resulted from the alpha particle scattering experiment
it was a positively charged nucleus surrounded by a cloud of negative electrons
142
describe the current model of the atom
The nucleus is tiny but it makes up most of the mass of the atom. It contains protons and neutrons, giving it an overall positive charge. The radius of the nucleus is about 10,000 times smaller than the radius of the atom.
The rest of the atom is mostly empty space. Negative electrons orbit the outside of the nucleus, travelling at extremely high speeds. They give the atom its overall size - the radius of an atom is about 1 x 10^-10 m.
The number of protons = the number of electrons, as protons and electrons have an equal but opposite charge and atoms have no overall charge.
Electrons in energy levels can move within (or sometimes leave) the atom. If they gain energy by absorbing EM radiation they move to a higher energy level, further from the nucleus. If they release EM radiation, they move to a lower energy level that is closer to the nucleus.
143
what is ionising radiation?
radiation that knocks electrons off atoms, creating positive ions. The ionising power of a radiation source is how easily it can do this.
144
give an example of how alpha radiation is used, and explain how it works
alpha radiation is used in smoke detectors - it ionises air particles, causing a current to flow. If there is smoke in the air, it binds to the ions - meaning the current stops and the alarm sounds
145
what is the symbol for beta radiation?
β
146
what is the symbol for alpha radiation?
⍺
147
what symbol is used to represent gamma radiation?
γ
148
what happens in the nucleus when a beta particle is emitted?
a neutron in the nucleus turns into a proton
149
what are beta emitters used for?
they are used to test the thickness of sheets of metal, as the particals are not immediately absorbed by the material like alpha radiation would be and do not penetrate as far as gamma rays.
150
how ionising is gamma radiation? why?
gamma radiation penetrates far into materials without being stopped and will travel a long distance through air. This means that they are weakly ionising because they tend to pass through rather than collide with atoms. Eventually they hit something and do damage
151
what are nuclear equations used for?
to show radioactive decay by using element symbols
152
how are nuclear equations written?
in the form:
| atom before decay -> atom after decay + radiation emitted
153
what rule do you have to remember when writing nuclear equations?
the total mass and atomic numbers must be equal on both sides
154
why are gamma rays released?
they are released as a way of getting rid of excess energy from a nucleus
155
how can radiation be measured?
with a Geiger-Muller tube and counter, which records the count-rate (the number of radiation counts reaching it per second)
156
what can half-life be used for?
it can be used to make predictions about radioactive sources, even though their decays are random. Half life can be used to find the rate at which a source decays (its activity)
157
what happens each time a radioactive nucleus decays to become a stable nucleus?
the activity as a whole will decrease (older sources emit less radiation)
158
give 2 common ways of reducing the effects of irradiation
keeping sources in lead-lined boxes and standing behind barriers when using sources. In some industries, the source may be in a different room and remote-controlled arms are used to handle it
159
why is contamination dangerous?
the contaminating atoms might then decay, releasing radiation which could cause you harm. Contamination is especially dangerous because radioactive particles could get inside your body.
160
what does the seriousness of irradiation and contamination depend on?
the source (different amounts of harm can be caused depending on the radiation type.
161
which types of radiation are the most dangerous outside the body? Why?
outside the body, beta and gamma sources are the most dangerous. This is because beta and gamma can penetrate the body and get to the delicate organs. Alpha is less dangerous because it can't penetrate the skin and is easily blocked by a small air gap - high levels of irradiation from all sources are dangerous, but especially from ones that emit beta and gamma
162
which type of radiation is most dangerous inside the body? Why is this?
inside the body, alpha sources are the most dangerous, because they do all their damage in a very localised area.
163
when working with alpha sources, is contamination or irradiation more dangerous?
contamination, rather than irradiation, is the major concern when working with alpha sources
164
describe an experiment to find a component's I-V characteristic
1. set up a circuit with an ammeter, a variable resister, and the component you want to test in series, and a voltmeter connected in parallel around the component.
2. Begin to vary the variable resister. This alters the current flowing through the circuit and the potential difference across the component
3. take several pairs of readings from the ammeter and voltmeter to see how the potential difference across the component varies as the current changes. Repeat each reading twice more to get the average pd at each current
4. swap over the wires connected to the cell, so the direction of the current is reversed, and repeat the experiment with a negative current
5. plot a graph of the current against voltage for the component.
