What are the two possible effects of heating a system?

It can raise the temperature of the system, or it can produce a change of state.

What is meant by the internal energy of a substance?

It is the total energy of all its particles, held both in their movement and in the forces between them.

What happens to the particles of a substance as its temperature rises?

They move faster, so their average kinetic energy increases.

A beaker of water is heated steadily. Its temperature rises until it boils and then stops rising. Explain why.

Before boiling the energy raises the kinetic energy of the particles, but at the boiling point it separates the particles instead, so the temperature holds steady.

OCR GCSE Combined Science Physics J250

Electricity

Topic overview Charge, and producing static electricity Transfer of electrons in charging and discharging Current as a rate of flow of charge Charge, current and time Series and parallel circuits, and circuit symbols Current, potential difference and resistance Resistors whose resistance changes, and investigating them Linear and non-linear circuit elements from graphs Net resistance in series and parallel Circuits for measurement, and electrical power

Energy

Topic overview Conservation of energy, and energy stores Energy changes on heating, and calculating them Energy of a moving body, a spring and a raised object Dissipation, and energy transfer in domestic devices Power ratings, efficiency, and increasing it Reducing unwanted energy transfer, and the rate of cooling

Forces

Global Challenges

Topic overview Typical speeds and everyday accelerations Reaction time, stopping distance and the dangers of large decelerations Stopping distance, acceleration and collision force calculations Energy resources, and trends in their use The national grid, and step-up and step-down transformers Why the national grid is efficient, and power in a transformer Mains electricity: a.c., d.c. and the domestic supply Live, neutral and earth wires, and electrical danger

Magnetism and Magnetic Fields

Topic overview Permanent and induced magnets, and magnetic poles Magnetic fields, and the dipping compass The magnetic effect of a current, and solenoids The motor effect and Fleming's left-hand rule The force on a conductor, and how a motor turns

Matter

Topic overview How the atomic model changed, and the structure of the atom The size of atoms, and defining density Density of the states of matter, and density calculations Conservation of mass in changes of state Heating a system, and specific heat capacity Calculations with specific heat capacity and latent heat Gas molecules, temperature and pressure

Radioactivity

Topic overview Protons, neutrons and isotopes Unstable nuclei and the emissions they give out Balancing nuclear equations Electron energy levels, and radiation from atoms Half-life and the randomness of decay Penetration of alpha, beta and gamma Contamination and irradiation, and reducing the hazard

Waves in Matter

Topic overview Amplitude, wavelength, frequency and period The wave equation Transverse and longitudinal waves Modelling waves with ripples and sound Electromagnetic waves as transverse, and energy transfer Frequency and wavelength across the spectrum What our eyes detect, and light as an electromagnetic wave Uses of electromagnetic waves Hazards of ultraviolet, X-rays and gamma rays Producing and receiving radio waves Absorption, transmission, refraction and reflection Investigating reflection and refraction of light

Matter

Heating a system, and specific heat capacity

3 things to know
Paper 11 (Physics)

Overview

The two effects of heating a system, internal energy and particle speed, why the temperature holds steady during a change of state, specific heat capacity and the specific latent heats of fusion and vaporisation with their units and when each is used, and the flat section of a cooling curve for stearic acid.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Which energy store increases when a system is heated?

Key term

Why does the temperature stay constant while a substance is changing state, even though heating continues?

Key term

How does cooling a system change its internal energy?

Questions from this subtopic

Each one with the model answer underneath.

1
What are the two possible effects of heating a system?
Model answer
It can raise the temperature of the system, or it can produce a change of state.
2
Which energy store increases when a system is heated?
Model answer
The internal energy store of the system.
3
What is meant by the internal energy of a substance?
Model answer
It is the total energy of all its particles, held both in their movement and in the forces between them.
4
What happens to the particles of a substance as its temperature rises?
Model answer
They move faster, so their average kinetic energy increases.
5
Why does the temperature stay constant while a substance is changing state, even though heating continues?
Model answer
The energy supplied is used to overcome the forces holding the particles together rather than to make the particles move faster.
6
A beaker of water is heated steadily. Its temperature rises until it boils and then stops rising. Explain why.
Model answer
Before boiling the energy raises the kinetic energy of the particles, but at the boiling point it separates the particles instead, so the temperature holds steady.

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