AQA GCSE (9-1) Physics: Particle Model of Matter

Key Takeaways for Particle Model of Matter

1. Density

Formula:
ρ=mVρ=Vm​

• Units:
  • Density: kg/m³ (kilograms per cubic metre).
  • Mass (mm): kg.
  • Volume (VV): m³.

Key Rules:

• Solids and liquids are denser than gases (closely packed particles).
• Example: Steel (high density) vs. wood (low density).

Tips:

• Unit conversion:
  • 1 g = 0.001 kg; 1 cm³ = 10−610−6 m³.
  • E.g., 135 g=0.135 kg135g=0.135kg.
• For irregular solids, use water displacement (volume displaced = object’s volume).

Common Experiment:

• Measure mass with a balance, volume via dimensions (cuboid: Volume=length×width×heightVolume=length×width×height) or displacement.

2. States of Matter

Examples:

• Ice (solid) → Water (liquid) → Steam (gas).
• Why gases are less dense: Particles are spaced out.

Exam Tip:

• Explain floating/sinking using density:
  • Cork floats (density < water); stone sinks (density > water).

3. Internal Energy & Changes of State

Internal Energy = Total kinetic + potential energy of particles.
Heating Effects:

1. Raises temperature (increases kinetic energy).
2. Changes state (increases potential energy).

Changes of State:

Key Rule:

• Temperature remains constant during state changes (energy used to break bonds).

4. Specific Heat Capacity (cc)

Formula:
ΔE=mcΔθΔE=mcΔθ

• Units:
  • Energy (ΔEΔE): J (joules).
  • Specific heat capacity (cc): J/kg°C.
  • Temperature change (ΔθΔθ): °C.

Example:

• Heating 200 kg water from 15°C to 45°C:
  ΔE=200×4200×30=25,200,000 J (25.2 MJ)ΔE=200×4200×30=25,200,000J(25.2MJ)

Tips:

• Water’s high cc (4200 J/kg°C) makes it good for heating systems (stores lots of energy).
• Memorise key cc values:
  • Aluminium = 880 J/kg°C; Copper = 380 J/kg°C.

5. Specific Latent Heat (LL)

Formula:
E=mLE=mL

• Units:
  • Specific latent heat (LL): J/kg.
  • Fusion (solid ↔ liquid); Vaporisation (liquid ↔ gas).

Example:

• Melting 8 g of ice (L=334,000 J/kgL=334,000J/kg):
  E=0.008×334,000=2672 JE=0.008×334,000=2672J

Exam Trick:

• Steam burns worse than boiling water: Extra energy (LL) released during condensation.

6. Gas Pressure & Particle Model

Key Principles:

• Gas particles move randomly, colliding with container walls (exerting force → pressure).
• Temperature ↑: Particles move faster → collisions harder/more frequent → pressure ↑.
• Boyle’s Law (constant temperature):
  P1V1=P2V2P1​V1​=P2​V2​
  • E.g., Halving volume doubles pressure.

Real-World Example:

• Bicycle pump heats up when compressed (work done → energy transferred to particles).

Experiment:

• Tin lid flying off when heated (water evaporates → gas pressure ↑).

7. Practical Tips for Exams

1. Unit Conversions: Always convert to kg, m³, or J before calculations.
2. Graphs:
   • Mass vs. Volume graph gradient = density.
   • Flat line on temp-time graph = state change.
3. Anomalous Results: Identify outliers in experiments (e.g., wrong material used).

Example Calculation (Density):

• Cuboid: Mass = 173.2 g (0.1732 kg), Volume = 10.1 cm×4.8 cm×1.3 cm=63.1 cm3=6.31×10−5 m310.1cm×4.8cm×1.3cm=63.1cm3=6.31×10−5m3.
  ρ=0.17326.31×10−5≈2744 kg/m3ρ=6.31×10−50.1732​≈2744kg/m3

Final Revision Checklist:

• Memorise ρ=mVρ=Vm​, ΔE=mcΔθΔE=mcΔθ, E=mLE=mL, and P1V1=P2V2P1​V1​=P2​V2​.
• Practice unit conversions and graph analysis.
• Understand particle arrangements in solids/liquids/gases.

50 GCSE Questions: Particle Model of Matter

Section 1: Density

1. Define density.
2. Convert 250 g to kg.
3. Calculate the density of a 2 kg object with a volume of 0.5 m³.
4. Why does 1 m³ of gas have less mass than 1 m³ of solid?
5. Describe an experiment to find the density of an irregularly shaped stone.

Section 2: States of Matter

6. List the three states of matter.
7. Explain why gases are less dense than solids.
8. Draw particle diagrams for solid, liquid, and gas.
9. Why can’t liquids be compressed easily?
10. Why does ice float on water?

Section 3: Internal Energy

11. Define internal energy.
12. What happens to internal energy when a substance is heated?
13. Why does temperature remain constant during melting?
14. Name two changes of state that release energy.
15. Explain sublimation with an example.

Section 4: Specific Heat Capacity

16. Define specific heat capacity.
17. Calculate the energy required to heat 5 kg of water from 20°C to 80°C.
18. Why is water used in central heating systems?
19. A 3 kg aluminium block is heated by 15°C. Calculate the energy transferred.
20. Explain why concrete cools down faster than water.

Section 5: Latent Heat

21. Define specific latent heat of fusion.
22. Calculate the energy needed to melt 0.5 kg of ice (Lf=334,000 J/kgLf​=334,000J/kg).
23. Why does steam cause worse burns than boiling water?
24. Describe an experiment to measure the latent heat of vaporisation of water.
25. A heater supplies 100 kJ to melt 200 g of wax. Calculate LfLf​.

Section 6: Gas Pressure & Boyle’s Law

26. State Boyle’s Law.
27. Explain why gas pressure increases when temperature rises.
28. A gas has a volume of 2 m³ at 100 kPa. Calculate its volume at 200 kPa (constant temperature).
29. Why does a bicycle pump get hot during use?
30. Describe how particle motion causes gas pressure.

Section 7: Experiments & Practicals

31. Why is it better to measure a large volume of liquid in density experiments?
32. What is the resolution of a balance measuring to 0.1 g?
33. How would you measure the thickness of paper using a ruler?
34. Identify a source of error in measuring the density of a cuboid.
35. Why does a mass vs. volume graph for stones pass through the origin?

Section 8: Calculations & Problem-Solving

36. Calculate the density of a cuboid (mass = 173.2 g, dimensions = 10.1 cm × 4.8 cm × 1.3 cm).
37. Convert 50 cm³ to m³.
38. A rock displaces 30 ml of water. Calculate its volume in m³.
39. A gas holder has a volume of 240,000 m³ at 100 kPa. Calculate its volume at 800 kPa.
40. A 2 kg metal block absorbs 48,000 J and heats from 20°C to 40°C. Find its specific heat capacity.

Section 9: Applications & Real-World Examples

41. Explain why sweating cools the body.
42. Why do divers need to exhale while ascending?
43. How does a pressure cooker work?
44. Why does a tin lid fly off when heated?
45. Describe how a refrigerator uses latent heat.

Section 10: Advanced Concepts

46. Explain why anomalous results occur in density experiments.
47. What does a flat line on a cooling curve represent?
48. Why does helium float in air?
49. Compare the density of oil and vinegar in salad dressing.
50. How does the particle model explain gas expansion?

Detailed Answers

1. Density is mass per unit volume: ρ=mVρ=Vm​.
2. 250 g=0.25 kg250g=0.25kg.
3. ρ=20.5=4 kg/m3ρ=0.52​=4kg/m3.
4. Gas particles are spaced out; fewer particles in 1 m³.
5. Submerge the stone in water; measure displaced volume.
6. Solid, liquid, gas.
7. Gas particles are far apart, less mass per volume.
8. Solid: ordered lattice; Liquid: close but mobile; Gas: random, spread out.
9. Particles are already close; no space to compress.
10. Ice has lower density than water.
11. Internal energy = total kinetic + potential energy of particles.
12. Internal energy increases (kinetic/potential energy rises).
13. Energy breaks bonds; no temperature change.
14. Freezing, condensation.
15. Solid → gas directly, e.g., dry ice (CO₂).
16. Specific heat capacity: Energy needed to raise 1 kg by 1°C.
17. ΔE=5×4200×60=1,260,000 JΔE=5×4200×60=1,260,000J.
18. High specific heat capacity → stores/releases large energy.
19. ΔE=3×880×15=39,600 JΔE=3×880×15=39,600J.
20. Lower specific heat capacity → loses energy faster.
21. Latent heat of fusion: Energy to melt 1 kg of solid.
22. E=0.5×334,000=167,000 JE=0.5×334,000=167,000J.
23. Steam releases latent heat when condensing.
24. Boil water, measure mass loss & energy input: L=EmL=mE​.
25. Lf=100,0000.2=500,000 J/kgLf​=0.2100,000​=500,000J/kg.
26. Boyle’s Law: P1V1=P2V2P1​V1​=P2​V2​ (constant temperature).
27. Faster particles → more collisions → higher pressure.
28. V2=100×2200=1 m3V2​=200100×2​=1m3.
29. Work done on gas → increases particle kinetic energy.
30. Particles collide with walls, exerting force per unit area.
31. Reduces percentage error in measurements.
32. The smallest measurable change is 0.1 g.
33. Measure 100 sheets, divide total thickness by 100.
34. Inconsistent measurements of dimensions.
35. Zero mass = zero volume (proportional relationship).
36. Convert mass: 173.2 g=0.1732 kg173.2g=0.1732kg. Volume: 10.1×4.8×1.3=63.1 cm3=6.31×10−5 m310.1×4.8×1.3=63.1cm3=6.31×10−5m3. Density: ρ=0.17326.31×10−5≈2744 kg/m3ρ=6.31×10−50.1732​≈2744kg/m3.
37. 50 cm3=50×10−6=5×10−5 m350cm3=50×10−6=5×10−5m3.
38. 30 ml=30 cm3=3×10−5 m330ml=30cm3=3×10−5m3.
39. V2=100×240,000800=30,000 m3V2​=800100×240,000​=30,000m3.
40. c=48,0002×20=1200 J/kg°Cc=2×2048,000​=1200J/kg°C.
41. Sweat evaporates, absorbing latent heat from skin.
42. Expanding air in lungs → risk of lung damage.
43. High pressure raises boiling point → faster cooking.
44. Heating → gas pressure exceeds atmospheric pressure.
45. Absorbs latent heat to evaporate coolant, cooling the interior.
46. Measurement errors or impurities in the material.
47. Change of state (e.g., freezing).
48. Helium density < air density.
49. Oil (lower density) floats on vinegar.
50. Particles spread out → occupy larger volume.

Exam Tip: Practice unit conversions and formula rearrangements! Use ΔE=mcΔθΔE=mcΔθ, E=mLE=mL, and P1V1=P2V2P1​V1​=P2​V2​ for calculations.