Heat Transfer

Test yourself

Heat Transfer

Thermal energy can be transferred by conduction, convection, and radiation.

Thermal energy

If there is a temperature difference between objects, heat will transfer.
A common misconception is that heat travels ‘up’. This is wrong.
Heat transfers from a hotter object to a colder object.
The greater the temperature difference, the faster the transfer of heat.
Heat transfer will stop when both objects are the same temperature.
Other factors that affect the thermal energy transfer rate include:
- The surface area.
- The material.
There are three ways in which heat is transferred.

Radiation

All objects emit infrared radiation.
The hotter the object is, the more radiation it emits.
Radiation does NOT need particles, so it can travel through a vacuum.
Space is a vacuum and we can feel the Sun's radiation.
Infrared radiation is part of the electromagnetic spectrum.
Dark-matt surfaces are the best emitters and absorbers of radiation.
Shiny surfaces reflect radiation.
Thermal imaging cameras use infrared radiation to take photographs.
You feel the heat of a light bulb by radiation.

Conduction

Conduction occurs when particles in a solid are heated.
If a substance is able to conduct heat well, such as a metal, it is a good conductor of heat.
If a substance is unable to conduct heat well, such as plastic or newspaper, it is a poor conductor or an insulator.
- Plastic insulation is wrapped around electrical wires to prevent electric shocks.

How conduction works

As particles are heated, they gain energy and vibrate more.
As they vibrate, they collide and so transfer energy to the next particle.
Examples of this can be seen if you leave a cold spoon in a hot cup of tea:
- The spoon will become hot.
Pans become hot when you are cooking due to conduction.
A snowball will melt in your hand.

Convection

Convection occurs when particles in a fluid (liquids or gases) are heated.
As particles are heated, they gain energy.
- As they gain energy, they move around more and so take up more space and become less dense.
Less dense fluid will rise and be replaced by more dense fluid.
Examples are:
- A radiator.
- Central heating.
- Convection currents causing wind.
- The movement of the mantle inside the Earth.

Heat transfer

No heat transfer is ever 100% efficient.
You will always lose heat from an object.
We say that this heat is 'dissipated' into the surroundings.
- The heat is transferred to the air around you by convection, conduction, and radiation.

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.2.1Reproduction in Humans

1.2.2Male Reproductive System

1.2.3Female Reproductive System

1.2.4Gestation

1.2.5Pregnancy

1.2.6Puberty

1.2.7The Menstrual Cycle

1.2.8Reproduction in Plants

1.2.9Pollination

1.2.10Dispersal Method

1.2.11Variation

1.2.12Causes of Variation

1.2.13Inheritance

1.2.14Adaptations and Evolution

1.2.15Species & Selective Breeding

1.2.16Genetic Conditions

1.2.17End of Topic Test - Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.4.1Balanced Diets

1.4.2Vitamins & Minerals

1.4.3Protein

1.4.4Lipids, Oils and Fats

1.4.5Carbohydrates

1.4.6Starch

1.4.7Energy Needs

1.4.8Dietary Fibre

1.4.9Diseases Caused by Nutritional Deficiencies

1.4.10Digestion

1.4.11Plant Nutrition

1.4.12Enzymes in Digestion

1.4.13Required Practical - Enzymes in Digestion

1.5Plants & Photosynthesis

1.5.1Roots

1.5.2Photosynthesis

1.5.3Leaves

1.5.4Rate of Photosynthesis

1.5.5Testing the Rate of Photosynthesis

1.5.6Water Transport in Plants

1.5.7Translocation

1.5.8The Carbon Cycle

1.5.9Human Activities & Carbon Dioxide

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.1.1Particles

2.1.2States of Matter

2.1.3Changes of State

2.1.4Properties of States of Matter

2.1.5Diffusion

2.1.6Changing State

2.1.7Pressure

2.1.8Temperature Increase in a Gas

2.1.9Conservation of Mass

2.1.10Purity of Substances

2.1.11Pure Substances

2.1.12Evaporation

2.1.13Mixtures

2.1.14Separating Mixtures

2.1.15Distillation

2.1.16Chromatography

2.1.17Solubility

2.1.18Investigating Solubility

2.2Chemical Reactions

2.2.1Chemical Reactions

2.2.2Common Reactions

2.2.3Acids & Alkalis

2.2.4Reactions of Acids

2.2.5Testing for Hydrogen

2.2.6The pH Scale

2.2.7Titration

2.2.8End of Topic Test - Chemical Reactions

2.3Atoms, Elements, Compounds

2.3.1Atoms

2.3.2Elements

2.3.3Compounds & Mixtures

2.3.4Electron Configuration

2.3.5Chemical Symbols

2.3.6Chemical Formulae

2.3.7Conservation of Mass

2.3.8Vacuums

2.3.9Molecules

2.3.10End of Topic Test - Particles & Atoms

2.4The Periodic Table

2.4.1Physical Properties

2.4.2Chemical Properties

2.4.3The Periodic Table

2.4.4Metals

2.4.5Non-Metals

2.4.6Alkali Metals

2.4.7Halogens

2.4.8Oxides

2.4.9End of Topic Test - The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.6.1Ions

2.6.2Ionic Bonding

2.6.3State Symbols

2.6.4Balancing Chemical Equations

2.6.5Relative Formula Mass

2.6.6Calculating the Relative Formula Mass

2.6.7The Reactivity Series

2.6.8Carbon & The Reactivity Series

2.6.9Displacement Reactions

2.6.10Displacement Reactions - Halogens

2.6.11Alloys

2.6.12Metal Alloys

2.7Energetics

2.7.1Measuring Gas Production

2.7.2Observing a Colour Change

2.7.3Analysing Reaction Rates

2.7.4Factors Affecting the Rate of Reaction

2.7.5Catalysts

2.7.6Testing for Oxygen

2.7.7Energy Changes During Reactions

2.8Properties of Materials

2.8.1Testing for Gases

2.8.2Alloys

2.8.3Density

2.8.4Density of Solids, Liquids & Gases HyperLearning

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.4.1Circuit Symbols

3.4.2Resistors & Diodes

3.4.3Electric Current

3.4.4Measuring Current

3.4.5Potential Difference

3.4.6Series Circuits

3.4.7Parallel Circuits

3.4.8Resistance

3.4.9Charges

3.4.10Static Electricity

3.4.11Magnets

3.4.12Magnetic Fields

3.4.13The Earth's Field

3.4.14Electromagnetism

3.4.15Uses of Electromagnets

3.4.16Strength of Magnetic Fields

3.4.17Circuit Symbols HyperLearning

3.5Matter

3.6Space Physics

3.6.1The Sun

3.6.2The Planets

3.6.3Other Astronomical Bodies

3.6.4The Milky Way

3.6.5Beyond The Milky Way

3.6.6The Seasons

3.6.7Days, Months & Years

3.6.8The Moon

3.6.9Light Years

3.6.10End of Topic Test - Space

4Thinking Scientifically

4.1Models & Representations

4.1.1Strengths & Limitations of Models

4.1.2Symbols & Formulae to Represent Scientific Ideas

4.1.3Analogies in Science

4.1.4Changing Models – Atomic Theory

4.1.5Working Safely in the Lab

4.1.6Variables

4.1.7Writing a Hypothesis & Prediction

4.1.8Planning an Experiment

4.1.9Maths Skills for Science

4.1.10Drawing Scientific Apparatus

4.1.11Observation & Measurement Skills

4.1.12Types of Data

4.1.13Graphs & Charts

4.1.14Bias in Science

4.1.15Conclude & Evaluate

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