Study guide: AQA Physics Paper 1

📋 Course Outline

1. Atoms and Isotopes
2. Radioactivity and Nuclear Radiation
3. Changes of State and Density
4. Internal Energy and State Changes
5. Gas Motion and Pressure
6. Electrical Power and Energy Transfer
7. Current, Potential Difference and Resistance
8. Series and Parallel Circuits
9. Mains Electricity and Safety
10. Energy Stores and Power
11. Energy Conservation and Efficiency
12. National and Global Energy Resources

📖 1. Atoms and Isotopes

🔑 Key Concepts & Definitions

• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons.

★ Must-know

• An atom contains protons and neutrons in its nucleus, with electrons around the nucleus.

Further detail

• The conventional representation of a nucleus identifies its element and gives its proton number and mass number.

• Experimental evidence, including scattering experiments and James Chadwick’s work, led scientists to change the atomic model over time.

📖 2. Radioactivity and Nuclear Radiation

🔑 Key Concepts & Definitions

• Activity: The rate at which its unstable nuclei decay, measured in becquerels (Bq) using a Geiger–Müller tube.
• Half-life: The time taken for the number of undecayed nuclei, or the activity, to halve.

★ Must-know

📌 Alpha particles, beta particles and gamma rays differ in their penetration through materials, range in air and ionising power.

📌 Contamination is the unwanted presence of radioactive material on or inside an object, whereas irradiation is exposure to radiation without radioactive material being transferred.

Further detail

• A balanced nuclear equation conserves both the total atomic number and the total mass number.

• Publishing studies of radiation effects on humans and sharing findings with scientists allows results to be checked through peer review.

💡 Memory Hook

Contamination places radioactive material on or inside a person; irradiation exposes them to radiation without transferring radioactive material.

📖 3. Changes of State and Density

★ Must-know

📐 Formula - Density is calculated using $\rho = \frac{m}{V}$.

📌 In the particle model, particles in solids are closely packed in fixed arrangements, particles in liquids remain close but move past one another, and particles in gases are widely spaced and move freely.

• A change of state is reversible and changes a substance’s properties without changing its mass.

Further detail

• A required practical determines densities of regular and irregular solid objects and liquids by measuring their mass and volume with appropriate apparatus.

• Changes of state include:

  • melting
  • freezing
  • evaporating
  • condensing
  • subliming
  • deposition

📖 4. Internal Energy and State Changes

🔑 Key Concepts & Definitions

• Internal energy: The total kinetic energy and potential energy of all the particles in a system, stored in the atoms and molecules that make up the system.

★ Must-know

📐 Formula - The change in thermal energy is calculated using $\Delta E = mc\Delta\theta$.

📐 Formula - The energy transferred during a change of state is calculated using $E = mL$.

📌 Specific heat capacity describes the energy needed to change temperature, whereas specific latent heat describes energy transferred during a change of state.

Further detail

• Heating and cooling graphs can show temperature changes and plateaus during changes of state.

📖 5. Gas Motion and Pressure

📝 Essential Points

• Gas molecules move constantly and randomly, and increasing gas temperature increases their average kinetic energy.

• At constant volume, heating a gas increases particle kinetic energy and raises its pressure as particles collide with the container walls more forcefully.

📌 For a fixed mass of gas at constant temperature, increasing its pressure decreases its volume, while decreasing its pressure increases its volume.

💡 Memory Hook

Higher gas temperature → greater average particle kinetic energy → greater pressure at constant volume.

📖 6. Electrical Power and Energy Transfer

★ Must-know

📐 Formula - Electrical power is calculated using $P = VI$ or $P = I^2R$.

📐 Formula - Electrical energy transferred is calculated using $E = Pt$ or $E = QV$.

• The National Grid is a system of cables and transformers linking power stations to consumers, and raising potential difference reduces current and makes energy transfer more efficient.

Further detail

• Circuit appliances transfer energy into forms including the kinetic energy of motors and the thermal energy of heating devices.

• A domestic appliance’s power rating relates to the rate at which it transfers energy and changes energy stores while in use.

📖 7. Current, Potential Difference and Resistance

🔑 Key Concepts & Definitions

• Electric current: The rate of flow of electrical charge around a closed circuit.

★ Must-know

📐 Formula - Charge and current are related by $Q = It$.

• A potential difference from a source causes current, which has the same value at every point in a single closed loop.

📐 Formula - Potential difference, current and resistance are related by $V = IR$.

Further detail

📌 For a given potential difference, increasing a component’s resistance decreases the current through it.

📖 8. Series and Parallel Circuits

★ Must-know

• Components connected in series have the same current passing through them, while components in parallel have the same potential difference across each of them.

📐 Formula - The total resistance of two series components is $R_{\text{total}} = R_1 + R_2$.

• Adding resistors in series increases total resistance, whereas adding resistors in parallel decreases total resistance.

Further detail

• Series-resistor circuit problems can be solved by replacing the resistors with their equivalent total resistance.

💡 Memory Hook

Series components share current; parallel components share potential difference.

📖 9. Mains Electricity and Safety

★ Must-know

📌 Alternating current and voltage periodically change direction, whereas direct current and voltage remain in one direction; UK mains is alternating.

• The potential difference between the live wire and earth is about 230 V, while neutral wires and human bodies are at or close to earth potential, 0 V.

📌 A live wire can remain dangerous with the mains switch open because a connection between the live wire and earth can cause harm.

Further detail

• A three-core mains cable contains live, neutral and earth wires, which have different functions.

📖 10. Energy Stores and Power

🔑 Key Concepts & Definitions

• System: An object or a group of objects whose energy stores can change.
• Power: The rate at which energy is transferred or work is done, and one watt is one joule transferred per second.
• Specific heat capacity: The energy required to raise the temperature of a unit mass of a substance by one degree.

★ Must-know

📐 Formula - The kinetic energy of an object is calculated using $E_k = \frac{1}{2}mv^2$.

📐 Formula - The gravitational potential energy gained by an object raised above ground level is calculated using $E_p = mgh$.

Further detail

📐 Formula - The elastic potential energy stored in a stretched spring is calculated using $E_e = \frac{1}{2}ke^2$.

📖 11. Energy Conservation and Efficiency

★ Must-know

📌 Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed, so the total energy in a system does not change.

• Only some energy in a system is transferred usefully; the remainder is wasted, and unwanted energy transfers can be reduced.

📐 Formula - Efficiency is calculated using $\text{efficiency} = \frac{\text{useful power output}}{\text{total power input}}$.

Further detail

• The rate at which a building cools depends on the thickness and thermal conductivity of its walls.

• Ways to increase the efficiency of an intended energy transfer can be suggested and explained.

💡 Memory Hook

Unwanted energy transfer → dissipation; reducing it makes the intended transfer more efficient.

📖 12. National and Global Energy Resources

🔑 Key Concepts & Definitions

• Renewable energy resource: One that is replenished naturally.

★ Must-know

• Evaluating energy resources involves environmental and ethical issues as well as political, social and economic considerations and limitations.

Further detail

• Energy resources can be compared by their uses in transport, electricity generation and heating.

• The reliability of energy resources differs, and patterns and trends in their use can be explained.