Edexcel IGCSE Physics · Topics 1–8 — Revision Pack

1. Outline

Topic 1 Forces and motion has three parts. Know which points are for everyone and which are (P) only.

2. Movement and position

Scalars and vectors

• Scalar — magnitude only (e.g. distance, speed, mass, time, energy).
• Vector — magnitude and direction (e.g. displacement, velocity, acceleration, force, momentum).
• Force is a vector; resultant force along a line is found by adding forces in the same direction and subtracting those opposite.

Average speed

Acceleration

• u = initial velocity, v = final velocity, t = time taken.
• Unit of acceleration: m/s².

Distance–time graphs

• Gradient = speed (steeper → faster).
• Horizontal line → stationary.
• Straight sloping line → constant speed.

Velocity–time graphs

• Gradient = acceleration.
• Area under the graph (between the line and the time axis) = distance travelled.
• Horizontal line → constant velocity (zero acceleration).

3. Forces, shape and momentum

Newton’s second law

Unbalanced (resultant) force causes acceleration. Friction opposes motion.

Weight

g ≈ 10 N/kg on Earth (also written as 10 m/s²). Weight is a force (N); mass is scalar (kg).

Stopping distance

Stopping distance = thinking distance + braking distance.

• Thinking distance ↑ with speed and slower reaction (tiredness, alcohol, distractions).
• Braking distance ↑ with speed, mass, poor road / tyre condition, worn brakes.

Falling objects & terminal velocity

Weight acts downwards; air resistance upwards. As speed rises, drag rises until forces balance → resultant force = 0 → terminal velocity.

Hooke’s law & elastic behaviour

Initial linear region of a force–extension graph follows Hooke’s law (F = kx). Elastic behaviour: material returns to original shape when the deforming force is removed.

Momentum (P)

Unit: kg m/s. Momentum is conserved in collisions (if no external forces). Safety features (crumple zones, airbags) increase collision time → reduce force:

Newton’s third law (P): if A exerts a force on B, B exerts an equal and opposite force on A.

Moments (P)

Unit: Nm. Weight acts through the centre of gravity. Principle of moments: for equilibrium, total clockwise moment = total anticlockwise moment.

4. Key formulae & units

Units you must use (1.1 / 1.2P)

Mass

kg

Length / distance

m

Speed / velocity

m/s

Acceleration / g

m/s² or N/kg

Force / weight

N

Time

s

Moment (P)

Nm

Momentum (P)

kg m/s

Core formulae

5. Self-check questions

Try these yourself first. Answers are in the next section.

1. State one scalar and one vector quantity from motion.
2. A car travels 150 m in 12 s. What is its average speed?
3. On a velocity–time graph, what do the gradient and the area under the line represent?
4. A 2.0 kg mass accelerates at 3.0 m/s². Calculate the unbalanced force.
5. Define stopping distance and name two factors that increase braking distance.
6. What does the linear region of a force–extension graph show?
7. (P) A 0.50 kg ball moving at 4.0 m/s collides and stops in 0.020 s. Find the average force.
8. (P) A 12 N force acts 0.25 m from a pivot. Calculate the moment.

6. Self-check answers

1. Outline

2. Mains electricity

a.c. and d.c.

• a.c. (alternating current) — mains supply; direction reverses periodically.
• d.c. (direct current) — cells / batteries; current in one direction.

Safety features

Heating effect

Current in a resistor transfers electrical energy → thermal energy (temperature rises). Used in heaters, kettles, toasters, filament lamps.

Power and energy

Choose a fuse rating just above the normal operating current (I = P / V).

3. Energy and voltage in circuits

Series vs parallel

• Series: one path; same current through all components; voltages add. If one lamp fails, all go out — not ideal for domestic lighting.
• Parallel: same voltage across branches; currents add at junctions. Lamps can be switched independently — used for house lighting.
• Current is conserved at a junction. Current in metals = flow of electrons (negative).

Ohm’s law

Higher resistance → smaller current for a given voltage (qualitatively).

I–V characteristics

• Ohmic resistor / wire: straight line through origin (constant R).
• Filament lamp: resistance rises as filament heats → curve flattens.
• Diode: conducts mainly in one direction (forward bias).

LDR and thermistor

• LDR: resistance ↓ as light intensity ↑.
• Thermistor: resistance ↓ as temperature ↑ (NTC type used at IGCSE).

Lamps and LEDs can indicate that a current is flowing.

Charge and energy

Voltage = energy transferred per unit charge (1 V = 1 J/C).

For two resistors in series: currents equal; voltages share; R_total = R₁ + R₂. In parallel, voltages across components are equal.

4. Electric charge (P)

• Conductors (e.g. metals) allow charge to flow; insulators (e.g. plastics, rubber) do not.
• Insulators can be charged by friction — electrons transferred: one object gains electrons (negative), the other loses electrons (positive).
• Like charges repel; unlike charges attract.
• Electrostatic phenomena are explained by electron movement (protons stay fixed in the nucleus).

Dangers and uses

• Dangers: sparks when fuelling aircraft / tankers → fire risk; earthing / bonding reduces danger.
• Uses: photocopiers, inkjet printers (charged ink droplets steered onto paper).

5. Key formulae & units

Units you must use (2.1)

Current

A (ampere)

Charge

C (coulomb)

Energy

J (joule)

Resistance

Ω (ohm)

Voltage / p.d.

V (volt)

Power

W (watt)

Time

s

6. Self-check questions

1. State the difference between a.c. and d.c. and give one source of each.
2. A 230 V kettle has power 2.0 kW. Calculate the current and suggest a suitable fuse.
3. Why is domestic lighting wired in parallel rather than series?
4. Write Ohm’s law and rearrange to find resistance.
5. How does the resistance of an LDR change as it gets darker?
6. A current of 0.40 A flows for 50 s. How much charge passes?
7. (P) Explain how rubbing a plastic rod with a cloth can leave the rod negatively charged.
8. (P) Why is electrostatic charge a hazard when refuelling a tanker?

7. Self-check answers

1. Outline

2. Properties of waves

Transverse vs longitudinal

• Transverse: oscillations perpendicular to energy transfer (e.g. light, water waves, EM waves).
• Longitudinal: oscillations parallel to energy transfer — compressions & rarefactions (e.g. sound).
• Waves transfer energy and information without transferring matter.

Key definitions

• Amplitude — maximum displacement from the rest position.
• Wavelength (λ) — distance between adjacent identical points (e.g. crest to crest).
• Frequency (f) — number of waves per second (Hz).
• Period (T) — time for one wave; f = 1 / T.
• Wavefront — line joining points that are in phase.

Doppler effect

If a wave source moves relative to an observer, the observed frequency and wavelength change. Approach → higher f / shorter λ; recede → lower f / longer λ.

Reflection and refraction

All waves can be reflected and refracted. Refraction occurs when speed changes on entering a new medium (often with a change of direction).

3. The electromagnetic spectrum

Continuous spectrum including radio, microwave, infrared, visible, ultraviolet, X-ray and gamma. All travel at the same speed in free space (speed of light).

Order of increasing frequency / decreasing wavelength →

Visible colours (increasing f): red → orange → yellow → green → blue → indigo → violet.

4. Light and sound

Light

• Light is a transverse wave; can be reflected and refracted.
• Law of reflection: angle of incidence = angle of reflection (angles measured from the normal).
• Draw ray diagrams with a ruler; mark normal, i and r.

Total internal reflection (TIR)

• Occurs when light in a denser medium hits a boundary at i > c (critical angle).
• sin c = 1 / n.
• Used in optical fibres (communications) and reflecting prisms.

Sound

• Sound is longitudinal; needs a medium (cannot travel in vacuum).
• Can be reflected (echo) and refracted.
• (P) Human hearing: about 20 Hz – 20 000 Hz.
• (P) Oscilloscope + microphone: pitch ↔ frequency; loudness ↔ amplitude.

5. Key formulae & units

Units you must use (3.1)

Angle

°

Frequency

Hz

Length / wavelength

m

Wave speed

m/s

Time / period

s

6. Self-check questions

1. State one difference between transverse and longitudinal waves, with an example of each.
2. A wave has frequency 50 Hz and wavelength 2.0 m. Find its speed.
3. List the EM spectrum in order of increasing frequency.
4. Give one use and one hazard of ultraviolet radiation.
5. State the law of reflection.
6. A glass block has refractive index 1.5. Calculate the critical angle (2 s.f.).
7. Why can astronauts not hear each other in space without radios?
8. (P) What is the approximate frequency range of human hearing?

7. Self-check answers

1. Outline

2. Energy transfers

Energy stores

Chemical, kinetic, gravitational, elastic, thermal, magnetic, electrostatic, nuclear.

Transfer pathways

Mechanically, electrically, by heating, by radiation (light and sound).

Conservation of energy

Energy cannot be created or destroyed — only transferred or stored differently. Total energy stays the same.

Efficiency

Sankey diagrams show energy flow: arrow width ∝ energy; wasted energy branches off.

Thermal energy transfer

• Conduction — mainly in solids; vibrating particles pass energy.
• Convection — fluids; hot fluid rises, cooler fluid sinks (convection currents) — e.g. room heaters, boiling water.
• Radiation — infrared; no medium needed. Dark / matt surfaces absorb and emit better than light / shiny ones. Hotter surfaces radiate more.

Reduce unwanted transfer with insulation, loft insulation, double glazing, cavity wall insulation, draught excluders.

3. Work and power

Work done

Work done = energy transferred. Distance must be in the direction of the force. Unit: J.

Gravitational potential energy

Kinetic energy

Conservation links GPE, KE and work (e.g. falling object: loss in GPE ≈ gain in KE if drag negligible).

Power

Power = rate of energy transfer / rate of doing work.

Unit: watt (W). 1 W = 1 J/s.

4. Energy resources & electricity generation (P)

*Nuclear fuel is finite, so treated as non-renewable in IGCSE comparisons, though uranium is not a fossil fuel.

Typical chain for thermal power stations: chemical/nuclear store → thermal → kinetic (turbine) → electrical.

5. Key formulae & units

Units you must use (4.1)

Mass

kg

Energy / work

J

Length / height

m

Speed

m/s

Acceleration / g

m/s²

Force

N

Time

s

Power

W

6. Self-check questions

1. Name three energy stores and two transfer pathways.
2. A lamp wastes 80 J thermally for every 20 J of useful light. Calculate its efficiency.
3. How do conduction, convection and radiation differ?
4. A force of 50 N moves an object 3.0 m in the direction of the force. Find the work done.
5. Calculate the GPE gained when a 2.0 kg mass is lifted 5.0 m (g = 10 N/kg).
6. A 0.40 kg ball moves at 5.0 m/s. Calculate its kinetic energy.
7. An appliance transfers 1200 J in 10 s. What is its power?
8. (P) Give one advantage and one disadvantage of wind power compared with coal.

7. Self-check answers

1. Outline

Topic 5 Solids, liquids and gases has four parts. Change of state and specific heat capacity are Physics-only (P).

2. Density and pressure

Density

• ρ = density (kg/m³)
• m = mass (kg)
• V = volume (m³)
• Practical: measure mass (balance) and volume (ruler for regular shapes, or displacement for irregular solids / measuring cylinder for liquids).

Pressure

• P = pressure (Pa or N/m²)
• F = force (N)
• A = area (m²)
• At a point in a gas or liquid at rest, pressure acts equally in all directions.

Liquid / fluid pressure difference

• p = pressure difference (Pa)
• h = height / depth (m)
• ρ = density of the liquid (kg/m³)
• g = gravitational field strength (N/kg or m/s²)
• Deeper → larger pressure; denser liquid → larger pressure at the same depth.

3. Change of state

This section is Physics-only (P).

Particle arrangement and motion

Heating a system

• Energy transferred by heating increases the energy stored in the system.
• That energy may raise temperature or cause a change of state (at constant temperature while melting or boiling).
• Melting: solid → liquid (particles overcome forces holding them in a lattice).
• Evaporation / boiling: liquid → gas (particles escape into the gas phase).
• Practical: temperature–time graph shows a flat section during a change of state.

Specific heat capacity (P)

Energy needed to raise the temperature of 1 kg of a substance by 1 °C (unit: J/kg °C).

• ΔQ = change in thermal energy (J)
• m = mass (kg)
• c = specific heat capacity (J/kg °C)
• ΔT = temperature change (°C)
• Practical: investigate c for water and solids (e.g. energy supplied / (m × ΔT)).

4. Ideal gas molecules

Pressure from molecular motion

• Gas molecules move with random motion (Brownian motion of smoke/dust particles is evidence of continuous collisions with air molecules).
• Collisions with container walls exert a force → this creates pressure.
• Higher temperature → higher average molecular speed → more forceful / frequent collisions → higher pressure (at fixed volume).

Absolute zero and the Kelvin scale

• Absolute zero = −273 °C — the lowest possible temperature (minimum molecular kinetic energy).
• Kelvin temperature is proportional to the average kinetic energy of the molecules.
• Conversion: T(K) = θ(°C) + 273 and θ(°C) = T(K) − 273.

Gas laws (fixed mass of gas)

• At constant temperature: pressure and volume are inversely related (qualitative + calculation).
• At constant volume: pressure rises as Kelvin temperature rises (qualitative + calculation).

5. Key formulae & units

Units you must use (5.1 / 5.2P)

Temperature

°C or K

Energy

J

Mass

kg

Density

kg/m³

Length / area / volume

m / m² / m³

Speed / acceleration

m/s / m/s²

Force

N

Pressure

Pa

Specific heat capacity (P)

J/kg °C

Formula summary

6. Self-check questions

Try these yourself first. Answers are in the next section.

1. A metal block has mass 0.54 kg and volume 2.0 × 10⁻⁴ m³. Calculate its density.
2. A force of 120 N acts on an area of 0.030 m². What is the pressure?
3. Find the pressure difference at a depth of 2.5 m in water (ρ = 1000 kg/m³, g = 10 N/kg).
4. (P) How do particle arrangement and motion differ in a solid and a gas?
5. (P) How much energy is needed to raise 0.20 kg of water by 15 °C if c = 4200 J/kg °C?
6. Convert 27 °C to kelvin. Why must gas-law calculations use kelvin?
7. A fixed mass of gas at constant temperature has p₁ = 100 kPa and V₁ = 0.040 m³. If V₂ = 0.020 m³, find p₂.
8. Explain, using molecules, why heating a gas at constant volume increases its pressure.

7. Self-check answers

1. Outline

Topic 6 Magnetism and electromagnetism has four parts. Several electromagnetism and transformer points are Physics-only (P).

2. Magnetism

• Magnets attract and repel other magnets; they attract magnetic materials (e.g. iron, steel, nickel, cobalt).
• Like poles repel; unlike poles attract.
• Hard magnetic materials (e.g. steel): keep magnetism → permanent magnets.
• Soft magnetic materials (e.g. soft iron): magnetise and demagnetise easily → cores of electromagnets / transformers.
• A magnetic field line shows the direction of the force on a north pole; lines leave N and enter S; denser lines = stronger field.
• Some materials become magnetised when placed in a magnetic field (induced magnetism).
• A uniform field can be made between opposite poles of two permanent magnets facing each other (parallel, equally spaced field lines).

3. Electromagnetism

Current produces a field

• An electric current in a conductor produces a magnetic field around it.
• (P) Electromagnet: soft-iron core with a coil of wire; field stronger with more turns, larger current, and a soft-iron core.
• (P) Sketch field patterns for: straight wire, flat circular coil, and solenoid (inside a solenoid the field is strong and nearly uniform).

Motor effect

• A current-carrying wire in a magnetic field experiences a force (unless the current is parallel to the field).
• Used in simple d.c. motors and loudspeakers.
• Force increases if field strength or current increases, or if a longer length of wire is in the field; reversing current or field reverses the force.
• (P) A moving charged particle also feels a force in a magnetic field if its motion is not parallel to the field.

Fleming’s left-hand rule

Use the left-hand rule when the wire carries a current perpendicular to the magnetic field to predict the force direction.

4. Electromagnetic induction

Induced voltage

• A voltage is induced in a conductor or coil when it moves through a magnetic field, or when the magnetic field through it changes.
• Larger induced voltage if: stronger field, faster motion / faster change of field, or more turns on the coil.

Generators

• Electricity can be generated by rotating a magnet inside a coil, or rotating a coil in a magnetic field.
• Same factors affect the size of the induced voltage (speed of rotation, field strength, number of turns, coil area).

Transformers (P)

Transformer content is Physics-only.

• A transformer changes the size of an alternating voltage using different numbers of turns on primary and secondary coils (soft-iron core links the fields).
• Step-up: more secondary turns → higher Vs (used before long-distance transmission to reduce current and energy losses).
• Step-down: fewer secondary turns → lower Vs (used near homes / appliances).

• Vₚ, Vₛ = primary / secondary voltages (V)
• Nₚ, Nₛ = primary / secondary turns
• Iₚ, Iₛ = primary / secondary currents (A)
• For 100% efficiency, input power = output power.

5. Key formulae & units

Units you must use (6.1)

Current

A

Voltage

V

Power

W

Transformer formulae (P)

6. Self-check questions

Try these yourself first. Answers are in the next section.

1. State the difference between magnetically hard and soft materials, with one example of each.
2. How can two bar magnets produce a uniform magnetic field?
3. What happens to the force on a current-carrying wire if the current is reversed?
4. State Fleming’s left-hand rule (what each finger / thumb represents).
5. Give two ways to increase the voltage induced in a generator coil.
6. (P) A transformer has Np = 500 and Ns = 100. If Vp = 230 V, find Vs.
7. (P) Why are step-up transformers used in the transmission of electrical energy?
8. (P) For a 100% efficient transformer, Vp = 230 V, Ip = 2.0 A and Vs = 11.5 V. Find Is.

7. Self-check answers

1. Outline

Topic 7 Radioactivity and particles has three parts. There is no separate Physics-only block, but fission/fusion detail is examined carefully.

2. Atomic structure and radiation

Nucleus notation

• Atom: protons and neutrons in the nucleus; electrons outside.
• Atomic (proton) number Z = number of protons.
• Mass (nucleon) number A = protons + neutrons.
• Isotopes: same Z (same element), different A (different neutron number).
• Example notation: ¹⁴₆C means carbon with A = 14, Z = 6.

Types of ionising radiation

Alpha (α), beta (β⁻) and gamma (γ) are emitted from unstable nuclei in a random process. They can be distinguished by penetration and ionising power.

Effect on A and Z

• α emission: A decreases by 4; Z decreases by 2.
• β⁻ emission: A unchanged; Z increases by 1 (neutron → proton + electron).
• γ emission: A and Z unchanged (nucleus loses energy).
• Neutron emission: A decreases by 1; Z unchanged.
• Balance nuclear equations for mass number and charge (proton number).

3. Detection, half-life, uses and hazards

Detection and background

• Detect with photographic film or a Geiger–Müller (GM) tube.
• Background radiation comes from Earth (rocks, radon gas) and space (cosmic rays), plus small amounts from buildings, food and medical sources.
• Always subtract background count rate in experiments.

Activity and half-life

• Activity = number of decays per second; unit becquerel (Bq). Activity falls over time.
• Half-life: time for the activity (or number of undecayed nuclei) to fall to half its original value. Different for each isotope.
• After n half-lives, activity ≈ original / 2ⁿ. You may also read half-life from an activity–time graph.

Uses

• Medicine: tracers, radiotherapy, sterilising equipment.
• Industry: thickness gauges, smoke detectors (α), tracing leaks, dating (e.g. carbon-14).

Contamination vs irradiation; dangers

• Irradiation: exposure to radiation from an outside source (you are not made radioactive).
• Contamination: unwanted radioactive material gets onto or into an object / person.
• Ionising radiation can damage cells and tissue and cause mutations; radioactive waste needs careful long-term disposal (shielding, remote handling, secure storage).

4. Fission and fusion

Nuclear fission

• Nuclear reactions (fission, fusion, radioactive decay) can release energy.
• A U-235 nucleus can split when struck by a neutron → two radioactive daughter nuclei + a few neutrons + kinetic energy.
• If those neutrons hit further U-235 nuclei, a chain reaction can occur.

Reactor control

• Moderator: slows neutrons so they are more likely to cause further fission (e.g. water / graphite in many designs).
• Control rods: absorb neutrons to control the rate of the chain reaction (insert → slow; withdraw → speed up).
• Shielding: thick concrete / lead around the reactor absorbs ionising radiation and protects workers.

Nuclear fusion

• Fusion: light nuclei join to make a heavier nucleus; there is a loss of mass and a release of energy.
• Fission: a heavy nucleus splits into lighter nuclei.
• Fusion is the energy source for stars.
• Fusion does not happen at low temperature / pressure because protons repel electrostatically; very high KE is needed to get close enough.

5. Key formulae & units

Units you must use (7.1)

Activity

Bq

Distance (penetration)

cm

Time

s, min, or h

Useful relations (not algebraic formulae sheets)

• After 1 half-life → activity × ½; after 2 → × ¼; after 3 → × ⅛.
• α: A − 4, Z − 2  ·  β⁻: A same, Z + 1  ·  γ: A and Z unchanged.

6. Self-check questions

Try these yourself first. Answers are in the next section.

1. What is an isotope? Give the meanings of A and Z.
2. Which radiation is the most ionising, and which is the most penetrating?
3. Complete the changes in A and Z for α emission and for β⁻ emission.
4. A source has activity 640 Bq and half-life 3.0 hours. What is the activity after 9.0 hours?
5. Name two sources of background radiation.
6. Explain the difference between contamination and irradiation.
7. Describe the roles of the moderator and control rods in a fission reactor.
8. Why does nuclear fusion need very high temperatures?

7. Self-check answers

1. Outline

Topic 8 Astrophysics has four parts. Know which points are for everyone and which are (P) only.

2. Motion in the universe

Structure of the universe (largest → smaller) and how gravity keeps objects in orbit.

• The universe is a large collection of billions of galaxies.
• A galaxy is a large collection of billions of stars.
• Our solar system is in the Milky Way galaxy.
• Gravitational field strength g varies: it is different on other planets and the Moon from that on Earth (depends on mass and distance from the centre).

What gravity causes

Gravitational force causes:

• moons to orbit planets
• planets to orbit the Sun
• artificial satellites to orbit the Earth
• comets to orbit the Sun

Orbit shapes — learn the differences

• Planets: nearly circular; roughly in the same plane.
• Moons: orbit their planet; usually nearly circular.
• Comets: highly elliptical; often not in the planetary plane; move fastest near the Sun and slowest when far away.

Orbital speed

• v = orbital speed (m/s)
• r = orbital radius (m)
• T = time period (s)
• Circumference of a circle = 2πr; speed = distance ÷ time

3. Stellar evolution

Colour and surface temperature

• Stars can be classified by colour.
• Colour is related to surface temperature.
• Blue / white → hotter; yellow → medium (like the Sun); red → cooler.

Stars of similar mass to the Sun

• nebula → main-sequence star → red giant → white dwarf
• On the main sequence, the star is stable because of nuclear fusion in the core.

Stars more massive than the Sun

• nebula → main sequence → red supergiant → supernova → neutron star or black hole
• Only the most massive remnants become a black hole; less extreme cases end as a neutron star.

Physics-only (P)

• Absolute magnitude: brightness as if the star were at a standard distance (so different stars can be compared fairly).
• HR diagram (Hertzsprung–Russell): horizontal axis usually temperature / colour (hot on the left); vertical axis absolute magnitude / brightness.
• Main regions: main sequence (diagonal band), red giants / supergiants (upper right), white dwarfs (lower left).

4. Cosmology

The whole Cosmology section is Physics-only (P).

Big Bang theory

The universe began in an extremely hot, dense state and has been expanding ever since.

• Evidence 1 — red-shift: light from most distant galaxies is shifted toward longer (redder) wavelengths.
• Evidence 2 — CMB: cosmic microwave background radiation — leftover microwave glow from the hot early universe.

Doppler idea

If a wave source moves relative to an observer, the observed frequency and wavelength change. A galaxy moving away → longer observed wavelength → red-shift.

• Δλ = change in wavelength
• λ₀ = reference (rest / laboratory) wavelength
• v = velocity of the galaxy (recession speed)
• c = speed of light
• More distant galaxies → larger red-shift → larger recession speed → supports expansion of the universe.

5. Key formulae & units

Units you must use (8.1)

Mass

kg

Length / radius

m

Speed

m/s

Acceleration / g

m/s² or N/kg

Force

N

Time

s

Formula (1) — orbital speed

Formula (2) — red-shift (P)

6. Self-check questions

Try these yourself first. Answers are in the next section.

1. How are the universe, galaxies, stars and the solar system related? Which galaxy are we in?
2. Why is g different on the Moon from on Earth?
3. A satellite has orbital radius 7.0 × 10⁶ m and period 5800 s. What is its approximate orbital speed? (2 s.f.)
4. What are the main differences between a comet’s orbit and a planet’s orbit?
5. Which has the higher surface temperature: a red star or a blue star?
6. Write the evolutionary path of a Sun-like star from nebula to its final stage.
7. (P) Name the two main pieces of evidence for the Big Bang theory.
8. (P) Why does a larger red-shift for more distant galaxies support expansion of the universe?

7. Self-check answers