OCR GCSE Physics B (Twenty First Century)
OCR GCSE Physics B P6 Matter: Models and Explanations Exam Questions
Free OCR GCSE Physics B revision for P6 Matter: Models and Explanations: what you need to know, common mistakes and exam-style questions with answers. Covers the particle model, density, changes of state, specific heat capacity, specific latent heat, gas pressure, stretching materials, Hooke's law, fluid pressure and the Big Bang.
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About OCR GCSE Physics B P6 Matter: Models and Explanations
Chapter P6 uses the particle model to explain how matter behaves. On OCR Physics B you study how energy transfers change the temperature or state of a material, calculate density, specific heat capacity and specific latent heat, and explain gas pressure in terms of particle collisions. You also look at how materials stretch and compress under forces, including Hooke's law. Separate physics adds pressure in fluids and how scientific models help explain the solar system and the Big Bang. P6 links to energy transfers in P4. Examiners test calculations with these equations and particle explanations of heating, pressure and changes of state.
What you need to know
- P6.1 Energy and matter Heating a material raises its internal energy. Change in internal energy = mass x specific heat capacity x change in temperature, and energy to change state = mass x specific latent heat. Temperature stays constant during a change of state.
- P6.2 Density and the particle model Density = mass / volume. Solids and liquids have closely packed particles and are much denser than gases. Mass is conserved when a substance changes state.
- P6.2 Gas pressure Gas particles collide with container walls, exerting a force. Heating a gas at constant volume makes particles move faster, so collisions are more frequent and harder and pressure rises.
- P6.3 Materials under stress Force exerted by a spring = spring constant x extension. Up to the limit of proportionality extension is proportional to force, and energy stored in a stretched spring = 0.5 x spring constant x extension^2. Elastic deformation is reversed when the force is removed; plastic deformation is not.
- P6.4 Pressure in fluids Separate physics only: pressure = force / area, and pressure in a liquid increases with depth (p = h x density x g), causing upthrust. For a fixed mass of gas at constant temperature, pressure x volume is constant.
- P6.5 The Big Bang Separate physics only: models based on gravity and the particle model help explain how the solar system formed, the orbits of planets, moons and satellites, and how the early Universe developed according to the Big Bang model.
Common mistakes in P6 Matter: Models and Explanations
- Saying temperature rises while a substance melts. Energy goes into breaking bonds between particles, so temperature stays constant.
- Saying particles expand when heated. Particles move faster and further apart; the particles themselves do not get bigger.
- Using length instead of extension in F = kx. Extension is stretched length minus original length.
- Mixing up specific heat capacity and specific latent heat. Heat capacity involves a temperature change; latent heat involves a change of state at constant temperature.
- Forgetting to convert cm3 to m3 or g to kg in density calculations. Check the units the answer needs.
Try three P6 Matter: Models and Explanations exam-style questions
1. A block has a mass of 0.50 kg and a volume of 2.0 x 10^-4 m3. Calculate its density. (2 marks)
Show the mark scheme answer
Density = mass / volume = 0.50 / 2.0 x 10^-4; = 2500 kg/m3.
2. Calculate the energy needed to raise the temperature of 2.0 kg of water by 15 °C. Specific heat capacity of water = 4200 J/kg °C. (2 marks)
Show the mark scheme answer
Energy = 2.0 x 4200 x 15; = 126 000 J.
3. A spring has a spring constant of 40 N/m and is stretched by 5.0 cm. Calculate the force and the energy stored. (3 marks)
Show the mark scheme answer
Extension = 0.050 m; F = 40 x 0.050 = 2.0 N; energy = 0.5 x 40 x 0.050^2 = 0.050 J.
P6 Matter: Models and Explanations FAQs
What does OCR Physics B P6 Matter: Models and Explanations cover?
It covers the particle model, density, specific heat capacity, specific latent heat, gas pressure and how materials deform under stress. Separate physics adds fluid pressure and models of the solar system and the Big Bang.
Which paper is it examined in?
OCR Physics B has two papers at each tier, Breadth in physics and Depth in physics, and both can assess content from every chapter, so P6 can appear on either paper.
What equations do I need for P6?
Key ones are density = m / V, energy = m x c x change in temperature, energy = m x L, F = kx and energy stored = 0.5kx^2; separate physics adds p = F / A, p = h x density x g and pV = constant.
