What happens to the energy of a system when it is heated?

Its thermal store increases, which normally raises its temperature.

Why does a pan of water take much longer to warm up than the metal pan holding it?

Water has a much higher specific heat capacity, so far more energy is needed for each degree of temperature rise.

What is meant by work done by a force?

The energy transferred when a force moves an object through a distance in the direction of the force.

A heavy box is dragged at a steady speed across a rough floor. Describe the energy change taking place.

Work is done against friction, transferring energy to the thermal stores of the box, the floor and the surrounding air.

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, and calculating efficiency Reducing unwanted energy transfer, and the rate of cooling

Forces

Topic overview Measuring distance and time, and calculating speed Converting units, and rates Vectors and scalars in motion Distance-time and velocity-time graphs Average speed, and the equations of uniform motion How objects interact, and forces as vectors Newton's first law Newton's second law Work done, and stored energy Power, and Newton's third law Stretching, bending and compressing; elastic and plastic Force and extension, linear and non-linear The spring constant, and work done in stretching Gravitational fields, weight and free fall Calculations with weight and gravitational field strength

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

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 Investigating reflection and refraction of light

Energy

Energy changes on heating, and calculating them

3 things to know
Paper 6 (Physics)

Overview

What heating does to the thermal store of a system, specific heat capacity and why water warms slowly, work done by a force against friction and in a heater filament, and calculations of work done, energy transferred electrically, energy to change temperature, and kilowatt-hours and their cost.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is work done by a force, and how does work warm a box dragged over a rough floor and a heater's filament?

Key term

What is meant by the specific heat capacity of a substance?

Key term

Two blocks of equal mass but different materials are given the same amount of energy. Which one reaches the higher temperature?

Questions from this subtopic

Each one with the model answer underneath.

1
What happens to the energy of a system when it is heated?
Model answer
Its thermal store increases, which normally raises its temperature.
2
What is meant by the specific heat capacity of a substance?
Model answer
The energy needed to raise the temperature of 1 kg of the substance by 1 °C.
3
Two blocks of equal mass but different materials are given the same amount of energy. Which one reaches the higher temperature?
Model answer
The block made of the material with the smaller specific heat capacity.
4
Why does a pan of water take much longer to warm up than the metal pan holding it?
Model answer
Water has a much higher specific heat capacity, so far more energy is needed for each degree of temperature rise.
5
What is meant by work done by a force?
Model answer
The energy transferred when a force moves an object through a distance in the direction of the force.
6
A heavy box is dragged at a steady speed across a rough floor. Describe the energy change taking place.
Model answer
Work is done against friction, transferring energy to the thermal stores of the box, the floor and the surrounding air.

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