GCSE Physics - AQA
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GCSE Physics - AQA - Marcador
GCSE Physics - AQA - Detalles
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| What are the 8 Energy Stores? | 1) Thermal energy stores 2) Kinetic energy stores 3) Gravitational Potential energy stores 4) Elastic Potential energy stores 5) Chemical energy stores 6) Magnetic energy stores 7) Electrostatic energy stores 8) Nuclear energy stores |
| What are the 4 ways Energy can be Transferred? | 1)Mechanically - a force doing work 2) Electrically - work done by moving charges 3) Heating 4) Radiation - Light or sound |
| What is a system? | An object or a group of objects |
| Kinetic Energy Equation | Ek = ½ mv² |
| Gravitational Potential Energy | Ep = mgh |
| Elastic Potential Energy Stores | Ee = ½ ke² |
| Specific Heat Capacity Definition | The amount of energy needed to raise the temperature of 1 kg of a substance by 1° |
| PRACTICAL: Specific Heat Capacity | 1) (For solids) Get a block of material with 2 holes in it 2) Measure its mass, then wrap it in insulating layer (thick layer of newspaper) to reduce energy transferred from block to the surroundings. Insert the thermometer and heater 3) Measure initial temperature of the block. Set PD to 10V. Turn on power, start stop watch 4) The current does work on the heater, transferring energy electrically to heaters thermal energy store. Energy is then transferred to materials thermal energy store by heating, therefore an increase in materials temperature 5) Measure its temperature every minute (keep an eye on ammeter - current shouldn't change) 6) Collect 10 readings then turn power off 7) Find materials SHC (Q9) 8) Repeat using different materials to see how their SCH's compare |
| How do I calculate Specific Heat Capacity (using data from the PRACTICAL) | 1) P = VI - to get power 2) E = Pt - to get energy transferred 3) ∆θ÷∆E - to get gradient 5) 1÷ (gradient × mass of block) - to get SCH |
| What is are the Equation's for Power? | P = E ÷ t / P = W ÷ t P = V x I |
| Define Conduction | The process where vibrating particles transfer energy to neighbouring particles 1) Energy is transferred to the thermal store of an object by heating, and then shared across the kinetic energy stores of the particles in object 2) Particles in the object vibrate more and collide with each other, these collisions cause energy to be transferred the particles kinetic energy stores. This is conduction NOTE: Happens in Solids, Gas' and Liquids |
| Define Convection | Where energetic particles move away from hotter to cooler regions 1) Energy is transferred by heating to the thermal store of liquid or gas 2) The heated particles move faster and the space between each particle increases causing the density of the region to decrease 3) Because liquids and gases can flow, the warmer, less dense regions rise above denser cooler regions. If there's a constant heat source, a convection current can be made (e.g. radiators) NOTE: Only happens in gas' and liquids |
| Reducing Unwanted Energy Transfers | Lubrication - Reduces energy dissipated due to frictional forces. Done by coating object in a liquid (e.g. oil), allowing them to flow easily Insulation - Reduces rate of energy transfer by heating |
| 4 Examples of Thermal Insulation | 1) Cavity wall - (inner and outer wall, gap in middle) air gap reduces energy transferred through conduction. Cavity wall insulation - gap is filled with foam, reduces energy transfer by convection 2) Loft insulation - Laid across loft floor and ceiling (e.g. fibreglass - which has pockets of trapped air). Reduces energy lost through conduction & prevents convection currents from being made 3) Double glazed windows - work in the same way as cavity wall 4)Draught excluders - around doors and windows reduce energy transfers by convection |
| How many atoms can fit inside a Centimetre? | 100,000,000 |
| Equation for Density | Density = Mass ÷ Volume (OR) P = m ÷ V |
| What is Density? What is the Density of: Iron, ice, water & air? | The amount of mass per unit volume it describes how closely packed the particles are in a solid, liquid or gas and depends on: - The state of matter - The material |
| How do you Calculate Volume of a: Cube, Sphere, Cylinder & Cone? | NOTE: For irregular shapes, volume can be measured using a displacement can... |
| PRACTICAL: Density | Method 1: Regular solids 1) Use a ruler to measure the length (l), width (w) and height (h) of a steel cube/Use vernier callipers to measure the diameter of the sphere. 2) Place the steel cube/metal sphere on the top pan balance and measure its mass. 3) Calculate the volume of the cube using (l × w × h) / sphere - (4÷3)πr³ 4)Use the measurements to calculate the density of the metal Method 2: |
| What are the 14 Circuit Components? | View image: |
| What are the 7 Main Circuit Components? | 1) Switch - Turns circuit on (closed) and off (open) 2) Lamp - Electric current heats the filament in a bulb so that it gives out light 3) Fixed Resistor - Restricts the flow of electrical current, has fixed resistance 4) Variable Resistor - Moving the position of its slider changes the resistance, used in some dimmer switches and volume controls 5) Thermistor - Resistance of a thermistor depends on temp. Low temp - high resistance... used in thermostats or heat activated alarms 6) Light-dependent resistor (LDR) - Resistance of a LDR depends on light intensity. Low light - high resistance... Used in sensors in cameras, automatic lights (turn on in dark) 7) Semiconductor Diode - allows current to flow in one direction. Converts an AC into a DC |
| Which way does Current flow in AC's & in DC's? | Direct Current - the flow of electrons is consistently in one direction around the circuit Alternating Current - the direction of electron flow continually reverses |
| Charge & Current | Charge - Electrons are negatively charged particles that transfer energy through wires electrically. Charge is a property of a body which experiences a force in an electric field. Charge is measured in coulombs (C). One coulomb - 6,250,000,000,000,000,000 - Ammeter - measures current (connected in series) Current - When current flows, work is done. Electrical current is a flow of electrons. The amount of charge passing a point in a circuit can calculated using: Q = I × t - Charge (Q) measured in (C) - Current (I) measured in (A) - Time (t) measured in (s) |
| Potential Difference & Resistance | PD - Current through a component depends on resistance & PD across the component. To measure PD, use a voltmeter, connected in parallel (voltage, volts - V) V = E ÷ Q - Potential difference (V) is measured in volts (V) - Energy (E) is measured in joules (J) - Charge (Q) is measured in coulombs (C) Resistance - When a charge moves through a PD, electrical work is done and energy is transferred: V = I × R PD (V), Current (A), Resistance (Ω) |
| PRACTICAL: Investigating Factors that Affect Resistance | 1) Connect the circuit as shown in the diagram below. 2) Connect the crocodile clips to the resistance wire, 100 centimetres (cm) apart. 3) Record the reading on the ammeter and on the voltmeter. 4) Move one of the crocodile clips closer until they are 90 cm apart. 5) Record the new readings on the ammeter and the voltmeter. 6) Repeat the previous steps reducing the length of the wire by 10 cm each time down to a minimum length of 10 cm. (Wire may heat, burn skin - Don't touch 'R' wire whilst circuit is connected, allow wire time to cool) 7) Use the results to calculate the resistance of each length of wire by using R = V/I, where R is resistance, V is voltage and I is current. 8) Plot a graph of resistance against length for the resistance wire |
| ANALYSIS: Investigating Factors that Affect Resistance | Accuracy: - record the length of the wire accurately - measure and observe the potential difference and current - use appropriate apparatus and methods to measure current and potential difference to work out the resistance |
| PRACTICAL: Investigating Current - Voltage Graphs | 1) Connect the circuit as shown in the first diagram. 2) Ensure that the power supply is set to zero at the start. 3) Record the reading on the voltmeter and ammeter. 4) Use the variable resistor to alter the potential difference. 5) Record the new readings on the voltmeter and ammeter. 6) Repeat steps three to four, each time increasing the potential difference slightly. 7)Reverse the power supply connections and repeat steps two to six. 8) Plot a graph of current against potential difference for each component, Repeat the experiment but replace the fixed resistor with a bulb |
| 1- Plum Pudding Model | 1) Greek Philosopher, Democritus, believed atoms were small uncuttable pieces of matter (460-370 BCE) 2) JJ Thomson, 1897. Discovered the electron 3) Ball of positive charge with negative electrons embedded inside 4) Evidence to support this: solids cant be squashed ∴ atoms which make them up must be solid throughout; rubbing two solids often causes a static charge ∴ there must be something (electrons) on the outside of the atoms that can be transferred as atoms collide |
| How many atoms can fit inside a Centimetre? | 100,000,000 |
| Equation for Density | Density = Mass ÷ Volume (OR) P = m ÷ V |
| 2- Gold Foil Experiment | 1) 1905, Ernest Rutherford's students directed a beam of (+ charge) alpha particles at a very thin gold leaf suspended in a vacuum (vacuum meant any deflection of the alpha particles would only be because of collisions with the gold foil) |
| What is Density? What is the Density of: Iron, ice, water & air? | The amount of mass per unit volume it describes how closely packed the particles are in a solid, liquid or gas and depends on: - The state of matter - The material |
| PRACTICAL: Density - Regular solids | 1) Use a ruler to measure the length (l), width (w) and height (h) of a steel cube/Use vernier callipers to measure the diameter of the sphere. 2) Place the steel cube/metal sphere on the top pan balance and measure its mass. 3) Calculate the volume of the cube using (l × w × h) / sphere - (4÷3)πr³ 4)Use the measurements to calculate the density of the metal |
| PRACTICAL: Density - Stone/Irregular solids | 1) Place the stone on the top pan balance and measure its mass 2) Fill the displacement can until the water is level with the bottom of the pipe 3) Place a measuring cylinder under the pipe ready to collect the displaced water 4) Carefully drop the stone into the can and wait until no more water runs into the cylinder 5) Measure the volume of the displaced water 6) Use the measurements to calculate the density of the stone |
| PRACTICAL: Density - Liquids | 1) Place the measuring cylinder on the top pan balance and measure its mass 2) Pour 50 cm3 of water into the measuring cylinder and measure its new mass 3) Subtract the mass in step 1 from the mass in step 2. This is the mass of 50 cm3 of water 4) Use the measurements to calculate the density of the water |
| What is the Equation for Density | Density = mass ÷ volume |
| Stable Nuclei | 1- Elements with fewer protons (near the top of the table) are stable if no. of neutrons = no. of protons 2- As no. of protons increases, more neutrons are needed to keep the nucleus stable 3- Nuclei with too many/few neutrons naturally exist but are stable and decay by emitting radiation |
| ALPHA PARTICLES | 1) Emitted when nucleus has too few neutrons, 2 neutrons + 2 protons emitted (Helium-4 nucleus) 2) Decreases Mass No. by 4 & decreases Atomic No. by 2 |
| BETA PARTICLES | 1) Emitted when nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron called a Beta (β) particle - this process is known as beta radiation. 2) A beta particle has a relative mass of zero, so its mass number is zero |
| GAMMA PARTICLES | 1) After alpha/beta particle is emitted, the nucleus will be too hot & will lose energy by emitting Gamma rays (rather than infrared radiation or EM waves - which are emitted due to hot gas) 2) Emission: Since energy levels in the nucleus are much higher than those in a gas, the nucleus emits a more energetic EM wave called a gamma ray. 3) Causes no change in no. of particles in the nucleus therefore atomic and mass number remain the same |
| How is Radioactive decay detected? | All types of radioactive decay can be detected by a Geiger-Muller tube, or G-M tube. The radiations ionise the gas inside and the resulting charged particles move across the chamber and get counted as charges rather like an ammeter |
| NEUTRON EMISSION | 1) Occasionally emitted by radioactive decay: - Naturally: absorption of cosmic rays high up in the atmosphere can result in neutron emission - Artificially: James Chadwick alpha particle fired at Beryllium resulted in neutrons emitted from that - Nuclear Fission Reactions: Neutrons released from parent nucleus as it splits 2) Neutron emission causes decrease by 1 in mass no. of nucleus, but no change in atomic no. |
| Half Life | Half-life is the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve. Count-rate is the number of decays recorded each second by a detector, such as the Geiger-Muller tube - This process continues and does not drop to zero completely |
| Nuclear Equations | Nucleus changes into new element by emitting alpha/beta particles. These changes can be described using nuclear equations NOTE: Gamma is pure energy and will not change the structure of the nucleus in any way |
| What is Irradiation? | Irradiation - Exposing objects to beams of radiation. Irradiation from radioactive decay can damage living cells. This can be useful and hazardous. |
| Uses of Irradiation | Irradiation for Sterilisation: To preserve fruit in supermarkets, exposed to a radioactive source (cobalt-60). The gamma rays emitted destroy any bacteria on the fruit, but don't change it in any significant way. This process doesn't cause the object to become radioactive Medical Irradiation: - Sterilisation of surgical instruments - beams of gamma rays (called gamma knife), can be used to kill cancerous tumours deep inside body Beams are aimed at tissue from many directions to maximise dose on tumour and minimise dose surrounding soft tissue. Healthy tissue can be damaged, so calculations are done to get the best dose - enough to kill tumour, but not so much that healthy tissue is damaged. |
| In Medical Applications that use Radioactive sources, How are long-term effects avoided? | Considering: 1) The nature of the decay (alpha, beta, gamma) 2) The half-life (long enough for the isotope to produce useful measurements, but short enough for the radioactive sources to decay to safe levels soon after use) 3) Toxicity If the half-life chosen is too long, the damaging effects of the radiation would last for too long and the dose received would continue to rise |
| Advantages and disadvantages of irradiation | Advantages: -sterilisation can be done without high temperatures -it can be used to kill bacteria on things that would melt Disadvantages: -it may not kill all bacteria on an object -it can be very harmful - standing in the environment where objects are being treated by irradiation could expose people’s cells to damage and mutation |
| Medical Contamination | Medical Contamination: 1) Radioactive source (technetium-99) injected, used as tracers to make softer tissue (blood vessels, kidney) show up through medical imaging processes. An isotope that emits gamma rays, which easily pass through body to a detector (e.g. x-ray/gamma camera). The radioactive isotope can be followed as it flows through a particular process in the body. 2) Changes in amount of gamma emitted from different parts, indicate how well isotopes are flowing or if there's a block. 3) Isotopes chosen must: - Have very short half-lives - sources used typically have half-lives of hours so after a couple of days there will hardly be any radioactive material left in a person’s body - Not be poisonous |
| Contamination to check for leaks | Water supplies can be contaminated with a gamma-emitting radioactive isotope to find leaks in pipes . Where there is a leak, contaminated water seeps into the ground, causing a build-up of gamma emissions in that area which can be found using a Geiger-Muller tube. This makes it easier to decide where to dig to find the leak Isotopes chosen must: - Emit gamma - have a half-life of at least several days to allow the emissions to build up in the soil - not be poisonous to humans as it will form part of the water supply |
| Effects of Radiation on the Body | Radioactive materials are hazardous. Nuclear radiation can ionise chemicals within a body, which changes the way the cells behave. It can also deposit large amounts of energy into the body, which can damage or destroy cells completely |
| Precautions taken to Reduce Risk of Using Radioactive Sources | 1) keep radioactive sources like technetium-99 shielded (preferably in a lead-lined box) when not in use 2) wear protective clothing to prevent the body becoming contaminated should radioactive isotopes leak out 3) avoid contact with bare skin and do not attempt to taste the sources 4) wear face masks to avoid breathing in materials 5) limit exposure time - so less time is spent around radioactive materials handle radioactive materials with tongs in order to keep a safer distance from sources 6) monitor exposure using detector badges, etc |
| Background Radiation | Radioactive materials occur naturally and, as a result, everyone is exposed to a low-level of radiation every day. This exposure comes from a mixture of natural and man-made sources - Amount of radiation your exposed to depends on where you live, your job... - Scientist must consider amount of BGR when working/experimenting with radioactive sources - BGR mainly effects people by irradiation, but small amount is from contamination by radioisotopes in food/drink consumed |
| Measuring Radiation | Simplest measure of radioactivity - Becquerel(Bq). Measures activity of nucleus. Activity - no. of decays per second from an unstable nucleus. However this particle could be alpha/beta ∴ have a different effect on the body: - Beta particle has lot of energy but may not cause lots of damage due to its low ionisation power - Alpha has less energy but cause more damage in a shorter distance as its bigger Sievert (Sv) is the unit to measure radiation dose and is the amount of damage that would be caused by the absorption of 1 joule of energy per kilogram of body mass. Usually absorption is less than 1 Sv, so milliSieverts (mSv) are often used instead. 1,000 mSv = 1 Sv. |
| Nuclear Fission | Nuclear fission - the splitting of a large atomic nucleus into smaller nuclei 1) In a nuclear reactor, a neutron is absorbed into a nucleus (uranium-235). Causing nucleus to become uranium-236 => violently unstable 2) Nucleus splits into 2 large fragments - daughter nuclei & 2/3 neutrons explode out of the fission reaction & can collide with other uranium nuclei to cause more fission reactions - Chain reaction 3) The fast moving neutrons carry most of the energy from the reaction with them (99%) but before the neutrons can collide with fresh uranium nuclei, they need to be slowed down so that the energy can pass on to other components in the nuclear reactor, which is used to heat water to drive the turbines that turn the generators |
| Fission Reactors | A fission reactor contains a number of different parts: 1) nuclear fuel (the uranium isotope that will split when triggered by an incoming neutron) - the fuel is held in rods so that the neutrons released will fly out and cause nuclear fission in other rods 2) graphite core - graphite slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod 3) control rods - these are raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction 4) coolant - this is heated up by the energy released from the fission reactions and is used to boil water to drive turbines in the power station 5) concrete shield - the daughter products of the fission reaction are radioactive and can be a hazard Many of the features of the reactor are designed to control the speed of the reaction and the temperature inside the shielding. An uncontrolled fission reaction is the basis of an atomic bomb |
| Nuclear Fusion | Nuclear fusion - when two small, light nuclei join together to make one heavy nucleus. Fusion reactions occur in stars where two hydrogen nuclei fuse together under high temperatures and pressure to form a nucleus of a helium isotope 1) Many nuclear fusion reactions are happening on the sun. E.g 4 hydrogen nuclei become 1 helium nuclei, causing a missing mass which is converted into energy & radiated away (this is happening on the sun) 2) It is estimated that the sun releases 3.8 × 1026 joules of energy every second 3) Fusion requires fusing of nuclei - positive particles that repel each other when approaching as their the same charge ∴ nuclear fusion must happen quickly so that repulsion doesn't have tine to stop it from happening 4) Particles can travel quickly by being in a hot gas/plasma, the temperature of the hot gas or plasma needs to be at least 150,000,000 degrees Celsius (°C) for fusion to happen |
| Atoms | 1) Atoms radius - around 1 × 10^-10 metres 2) The total number of protons and neutrons is called the mass number(top) and the number of protons is called the atomic number(bottom) 3) An ion is an atom that has lost or gained one or more electron |
| Isotopes | 1) Amount of protons determines what element it is (e.g. 17 protons means Chlorine) 2) Isotopes are forms of an element that have the same number of protons but different numbers of neutrons (mass number changes) |
| Ions | 1) Normally, atoms are neutral. They have the same number of protons in the nucleus as they have electrons orbiting in the energy levels around the nucleus. 2) Atoms can lose or gain electrons due to collisions or other interactions forming charged particles called ions: - Loss of electron/s, positively-charged ion - Gain of electron/s, negatively-charged ion |
| 1- Plum Pudding Model | 1) JJ Thomson, 1897 discovered the electron 2) Atoms consisted of a positively charged ball with negative electrons embedded inside 3) Evidence to prove this: - Solids cant be squashed ∴ the atoms which make them up must be solid throughout - Rubbing 2 solids together can cause static charge ∴ there must be something (electrons) on the outside of atoms transferred as atoms collide NOTE: Before this Greek philosopher Demokritos (460-370 BCE) thpought matter was made up of tiny uncuttable pieces - atoms |
| 2- Gold Foil Experiment | 1) Ernest Rutherford, 1905. Directed a beam of (+charge)alpha particles at v. thin gold foil 2) Did this in a suspended vacuum ∴ any deflection of alpha particles would be due to collisions with the gold foil. 3) Most particles went straight through ∴ most of an atom is empty space 4) A few deflected by large angles (>4°) ∴ concentration of +charge in the atom (like charges repel) 5) Very few came straight back ∴ + charge and mass concentrated in a small volume (nucleus) |
| 4- Further Developments | Niels Bohr, 1913. 1) Electrons orbit nucleus at fixed distances/different energy levels from nucleus 2) Chemicals burn with certain-coloured flames ∴ the pattern of energy released by electrons in the chemical reaction, must be the same for every single atom of that element James Chanwick, 1912/1932 1) There was a difference between the atomic no. and atomic mass of an atom 2) ∴ there had to be a neutral particle the same size as the proton to keep the nucleus stable and make up the missing mass, scientist accepted this 20 years later - 1932 |
| How do you change the State of a material? | Adding or removing energy from a material can change its state - active process: e.g. boiling, people add energy - passive process: e.g. evaporation, liquid slowly absorbs energy from surroundings |
| Solids, Liquids, Gases | Solids: are in a regular arrangement, vibrate about a fixed position, sit very closely together Liquids: are randomly arranged, move around each other, sit close together Gases:are randomly arranged, move quickly in all directions, are far apart |
| State of a Matter | Already Know It |
| Whats Sublimation? | Material goes straight from solid to gas (without being liquid) |
| Whats internal energy? | Total amount of kinetic energy and potential energy of all the particles in the system. |
| Whats the Conservation of Energy? | Assuming no energy is lost to the environment, any energy transferred to a material will be distributed between the chemical store and the thermal store of the internal energy |
| Particle Motion 3 Facts | 1) The force acting on the container due to these collisions is at right angles to the container 2) The pressure from gas molecules may increase if there are more molecules colliding each second or if the molecules are moving faster 3) The pressure in the atmosphere (atmospheric pressure) at sea level is about 100,000 N/m2 |
| Equation for Pressure | Pressure = force ÷ area -Pressure (N/m^2) -force (N) -area (m^2) |
| Relationship between Pressure and Temperature | 1) the pressure of a gas increases as its temperature increases. As a result, the gas particles will be travelling faster and will collide with the walls of the container more frequently, and with more force ∴ pressure is directly proportional to temperature 2) If the temperature of a gas stays the same, the pressure of the gas increases as the volume of its container decreases because the same number of particles collides with the walls of the container more frequently as there is less space. However, the particles still collide with the same amount of force |
| Relationship between Pressure and Volume | 1) Inversely proportional. 2) pressure × volume = constant (pressure-Pa, Volume-m^3) 3) Robert Boyle poured mercury into a J-shaped tube (sealed on the lower end). He trapped a bubble of air, the volume of mercury in the higher column, the greater the pressure on the trapped air, the smaller the it became |
| Equation for Change in Pressure | P1 × V1=p2 × V2 |