Eduqas GCSE Physics 2 Particle Model of Matter Exam Questions

About Eduqas GCSE Physics 2 Particle Model of Matter

The particle model of matter in Eduqas GCSE Physics explains the properties of solids, liquids and gases using the arrangement and motion of particles. You learn density and how to measure it, changes of state, internal energy and the difference between heating that changes temperature and heating that changes state. Gas behaviour is a key part: how particle collisions cause pressure, how temperature affects volume and pressure, and Boyle's law, pV = constant for a fixed mass at constant temperature. Examiners often test density calculations and explanations of gas pressure, and two specified practicals, SP2A and SP2B, sit here.

What you need to know

• States of matter Solids have particles in fixed, close positions that vibrate; liquids have close particles that move past each other; gases have widely spaced particles moving rapidly and randomly. Changes of state are physical changes and mass is conserved.
• Density Density = mass / volume, in kg/m3 or g/cm3. SP2A: measure the density of regular solids using a ruler and balance, irregular solids by displacement of water in a measuring cylinder or eureka can, and liquids using a measuring cylinder on a balance.
• Internal energy Internal energy is the total kinetic and potential energy of the particles. Heating increases internal energy, raising the temperature or changing the state. During melting or boiling the temperature stays constant while bonds are broken.
• Gas pressure Gas particles collide with the container walls, exerting a force over an area, which is pressure. Higher temperature means faster particles, so more frequent and harder collisions and a higher pressure at constant volume.
• Gas volume and temperature At constant pressure, a gas expands when heated. SP2B: investigate how the volume of a gas varies with temperature, for example a trapped air column in a capillary tube in a water bath.
• pV = constant For a fixed mass of gas at constant temperature, pressure x volume is constant, so p1V1 = p2V2. Halving the volume doubles the pressure because particles hit the walls more often.

Common mistakes in 2 Particle Model of Matter

• Saying particles get bigger when heated. Particles move faster and further apart; their size does not change.
• Saying temperature rises while a substance is melting. Energy goes into breaking bonds, so the temperature stays the same until the change of state is complete.
• Mixing units in density calculations. Use g with cm3 or kg with m3, and remember 1 g/cm3 = 1000 kg/m3.
• Explaining gas pressure as particles colliding with each other. Pressure comes from collisions with the walls of the container.
• Using pV = constant when the temperature changes. It only applies to a fixed mass of gas at constant temperature.

Try three 2 Particle Model of Matter exam-style questions