Physics GCSE paper 1

how small is an atom

radius of 0.1nm

what is the radius of a nucleus relative to the atom

less than 1/10,000

what is the relative mass of an electron

1/2000

what happens when an atom absorbs electromagnetic radiation

the electrons may move to a higher energy level further from the nucleus

what happens when an atom emits electromagnetic radiation

the electrons may move to a lower energy level, closer to the nucleus

what is an isotope

atoms of the same element with same number of protons, but different numbers of neutrons

who had the first model of an atom and what was it

1803, Dalton - an atom is a solid sphere that cannot be created, destroyed or divided into smaller parts

different types of spheres make up different elements

JJ Thomspon

1897, plum pudding model - atom is not a solid sphere but a cloud of positive charge with negative electrons embedded in it

Nuclear Model and how it was proved

1909, Rutherford’s Alpha Scattering Experiment

fired alpha particles at a thin sheet of gold foil; most passed straight through, some were a bit deflected and some came straight back

tells us mass of an atom is concentrated in a central nucleus

nucleus is positively charged (repelled positively charged alpha particle)

most of the atom is empty space

Bohr electron shell model 1913

electrons orbit the nucleus at specific distances in ‘shells’/energy levels

what happened in 1920

the discovery of the proton

what happened in 1932

discovery of the neutron by James Chadwick

what is radioactive decay

when an unstable nuclei randomly emits radiation to become more stable

what are the different types of nuclear radiation

alpha particles

beta particles

gamma rays

neutrons

symbol, nature and change in nucleus of an alpha particle

alpha symbol, two neutrons and two protons (helium nucleus), nucleus loses two neutrons and two protons

symbol, nature and change in nucleus of beta radiation

beta symbol, fast-moving electron ejected from a nucleus, neutron decays into a proton and an electron

symbol, nature and change in nucleus of gamma ray

y symbol, electromagnetic radiation emitted from the nucleus, some energy transferred away

what is activity

the rate that an unstable nucleus decays (Bq)

what is count rate

the number of decays recorded per second by a detector e.g. Geiger-Muller tube

penetrating power, range in air and ionising power of alpha

stopped by skin/sheet of paper

less than 5cm

high ionising power

penetrating power, range in air and ionising power of beta

stopped by 3mm of aluminium foil

1 metre in air

low ionising power

penetrating power, range in air and ionising power of gamma

stopped by lead/concrete

more than 1km

very low

what does it mean that radioactive decay is a random process

it is impossible to predict which atom will decay next

what is half-life

the time taken for the number of nuclei of an isotope in a sample to halve / time taken for the count rate or activity of a radioactive source to halve

how can I calculate net decline

reduction in activity / initial activity

what is radioactive contamination

the unwanted presence of radioactive atoms on other materials

what is irradiation

the exposing of an object to nuclear radiation

how can we protect against contamination and irradiation

keep a distance from the radiation

limit the time of exposure to the source

use shielding

why is it important to publish findings

so that work can be peer reviewed

what is background radiation

radiation around us all the time

2 examples of a natural source of radiation

rocks and cosmic rays from space

2 examples of man-made radiation

nuclear accidents and nuclear fallout from weapons testing

what is radiation dose

a measurement of the health risk of exposure to radiation measured in sieverts (Sv)

what does radiation dose depend on

location and occupation

uses of nuclear radiation in medicine

• control or destruction of unwanted tissue

  • exploration of internal organs

how can nuclear radiation be used to explore internal organs

• gamma emitting tracer can be swallowed or injected into a patient

  • an image can be created using a gamma camera, showing where the tracer goes

how can nuclear radiation be used in the control or destruction of unwanted tissue

beams of gamma radiation can be focused on a tumour to destroy it

the beams will come from all directions, focused on the tumour - this maximises the radiation dose of the tumour and minimises the radiation dose of the surrounding tissue

the beams will diverge at the tumour

ensures that the surrounding tissue wont be too damaged

what is nuclear fission

• occurs when a large, unstable nucleus absorbs an extra neutrons and splits into

  • two lighter nuclei

  • two or three neutrons

  • gamma radiation

• all the products of nuclear fission have kinetic energy

• neutrons released during fission can be absorbed by other large, unstable nuclei to cause a chain reaction

what is spontaneous fission

when nuclear fission occurs without absorbing an extra nucleus

how do nuclear reactors work

energy released during fission is used to heat water

this turns to steam

steam turns a turbine, which turns a generator

this generates electricity

why is a graphite core necessary in a reactor

slows the neutrons so they are more likely to be absorbed by unstable nuclei

role of control rods in a reactor

absorb some neutrons to control the speed of the chain reaction

role of coolant in a reactor

contains water which is heated and boiled

how do nuclear weapons work

they make use of uncontrolled chain reactions

all of the neutrons released cause more fission, releasing more energy

this is very rapid and the energy released becomes so great that an explosion takes place

what is nuclear fusion

occurs when two light nuclei join together to form one heavier nucleus e.g. hydrogen to form helium

during the process, some mass is converted into energy and transferred in the form of radiation

where does nuclear fusion occur

on the sun - responsible for the energy given out

why is energy required to start nuclear fusion

to overcome the repulsion between the two positively charger nuclei

Kinetic energy

The energy of a moving object

GPE

the energy an object has when its raised above the ground

Elastic potential energy

the energy an elastic object has when its stretched or compressed

Internal (thermal) energy

total kinetic and potential energies of all the particles in an object

chemical energy

energy stored in chemical bonds

nuclear energy

energy stored in the nucleus of an atom

magnetic energy

energy a magnetic object has when its near to a magnetic field

electrostatic energy

energy that a charged object has when held near to another charged object

heating

energy transferred due to a difference in temperature - hot to cold

radiation

energy transferred as a wave

electrical work

energy transferred by the flow of charge due to a potential difference

mechanical work

energy transferred due to a force moving an object through a distance or changing its shape

equation for kinetic energy

KE = ½ x m x v2

equation for elastic potential energy

EPE = ½ x k x e2

equation for GPE

GPE = m x g x h

specific heat capacity

amount of energy required to raise the temperature of 1kg of the substance by one degree celcius

what is power

the rate at which energy is transferred

power equations (2)

P = E/t or P = W/t

what is the the same as energy transfer of 1 joule per second

1 watt

law of conservation or energy

energy can be transferred usefully, stored or dissipated but cannot be created or destroyed

energy dissipation

transferred to less useful stored - e.g. lightbulb and thermal energy

how can we reduce unwanted energy transfers

lubrication and thermal insulation

what does thermal conductivity tell us about a material

how quickly energy is transferred through the material via thermal conduction

what 3 things are the rate of energy transfer through a material dependent on

thermal conductivity, thickness of the material, difference in temperature (temperature gradient)

how could we increase the efficiency

increase the amount of useful energy transfer - streamlining, lubrication, stop frictions, etc.

what is a renewable energy resource

energy that can be replenished as they’re used up e.g. wind, geothermal and solar

what are non-renewable energy sources

energy source that is finite - cannot be replenished as it is used and will eventually run out

advantages and disadvantages of coal, natural gas and oil

enough currently available to meet out demand, relatively cheap to extract from underground, reliable

they are a finite resource and will run out, release carbon dioxide, release other pollutants e.g. sulphur dioxide - acid rain, risk of oil spills

advantages and disadvantages of nuclear fission

enough currently available to meet demand, no pollutant gases, reliable

nuclear waste is difficult to safely dispose of, nuclear waste is dangerous, nuclear power plants are expensive to build, run and decommission

advantages and disadvantages of solar power

cheap to run after initial installation, produces no pollutant gases

not reliable - dependent, installation is expensive

advantages and disadvantages of tidal

reliable, no pollutant gases, large amount of energy, no fuel costs

can damage marine habitats, installation is expensive, unable to control supply

advantages and disadvantages of hydro-electric energy

cheap to run, no fuel costs, reliable

high initial cost, destroys habitats when flood

advantages and disadvantages of wave

cheap to run, no fuel costs, no pollutant gases

can damage marine habitats, high installation cost, unable to control supply

advantages and disadvantages of wind power

cheap to run, no fuel cost, no pollutant gases

unable to control supply, noise pollution, a lot of turbines needed so a lot of land

advantages and disadvantages of geothermal energy

cheap to run, no fuel costs, no pollutant gases

installation is expensive, limited locations where it can be set up

advantages and disadvantages of biofuels

reliable (supply can be controlled), can be carbon neutral

can lead to deforestation, expensive to produce

arrangement of particles in a solid

• regular pattern

• very close together

• vibrate around fixed positions

arrangement of particles in a liquid

• random arrangement

• close together

• move freely around each other

particle arrangement in a gas

• random arrangement

• far apart

• move quickly in all directions

describe an experiment to find the density of an irregularly shaped object

• measure the mass of an object using a balance

• fill a displacement can to the point that the water is level with the bottom of the pipe

• place an empty measuring cylinder under the pipe

• drop the irregular shaped object into the water carefully

• wait until the water stops leaving the displacement can

• measure the volume of displaced water

• use the density equation

changes of state

physical changes where if the process is reversed, the material regains its original properties

what is internal energy

the energy stored inside a system by the particles that make up that system

equal to the total kinetic and potential energies of all the particles making up the system

what are the two ways a material will change when it is heated or cooled

1. material may change temperature - thermal energy store change

   1. chemical bonds may form or break - change in the chemical potential energy store

what 3 factors influence temperature change

1. type of material

2. the energy put into the system

3. the mass of the material

what is specific heat capacity

the amount of energy required to raise the temperature of 1kg of a substance by 1 degree

why doesn’t the temperature change when a substance changes state

because the internal energy changes

what is specific latent heat

the energy required to change the state of 1kg of a substance without changing the temperature

heating cooling graphs

horizontal lines mean that all of the energy is being put into breaking the bonds - none is going into changing the temperature of the substance

why does pressure increase where temperature increases

particles gain kinetic energy and so move faster

they collide with the walls more frequently thus exerting a greater total force

pressure and temperature are directly proportional

why do gases exert a pressure on the walls of a container

gas particles collide with walls - produces a net force at right angles to the walls of the container or surface - can cause a gas to be compressed or expanded

why does increasing volume decrease pressure

the distance that the particles can move in between collisions has increased

less frequent collisions between the particles and the walls of the container

decreases the total force and therefore pressure

pressure is ____ to volume

inversely proportional