Download ppt - U11 Heat Temperature

ESSENTIAL NATURAL SCIENCE 2Unit 11

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Heat and temperature

CONTENTS

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CONTENTS


Heat

DefinitionMeasurement

Effects of heat

Effects on matterExpansion and contractionChanges of state

Heat transfer

ConductionConductors and insulatorsConvectionRadiation

Temperature

Temperature and mearurementThermometersTemperature scales



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RESOURCES

Expansion and contraction

Changes of state

Temperature scales

Conduction

Convection Radiation

Heat Heat measurement

Conductors and insulators

Temperature and measurement

Thermometers

Effects of heat

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Heat

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Heat is the amount of thermal energy that is transferred from one body or system to another, due to a difference in temperature.

Heat is energy in transit.



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Heat

Heat is energy in transit.

Heat flow stops when their temperatures are the same, that is, thermal equilibirum.

Heat flows from the hot iron rod to the cold water.

Heat is the amount of thermal energy that is transferred from one body or system to another, due to a difference in temperature.

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Heat measurement

1 J = 0.24 cal

heat

Units of heat: joules (J)

calories (cal)

Heat is measured in units of joules or calories.

1 cal = 4.186 J



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Temperature and measurement

Temperature is the amount of heat in a system.

Temperature can be measured with a thermometer.



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Alcohol thermometer

Clinical thermometer

Thermometers

They are used to measure atmospheric temperature.

coloured alcohol

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They are used to measure body temperature. mercury

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Temperature scales

ºF ºC K Fahrenheit scale (ºF)

Celsius scale (ºC)

Kelvin or absolute scale (K)

212

176

140

104

68

32

373

353

333

313

293

273

100

80

60

40

20

0

Boiling point

Freezing point

water



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Effects of heat

Heat produces the following effects on matter:

Expansion

Contraction



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Effects of heat


Expansion: The increase in volume which occurs when a system gains heat.

Expansion

Contraction



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Effects of heat


Expansion

Contraction

Contraction: the decrease in volume which occurs when a system loses heat.



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The gas inside a balloon expands when heated.


The particles move more freely than in solids. Liquids usually expand more than soilds.

The particles are far apart and move more freely than in liquids. Gases usually expand more than liquids.

The particles are not free to move. Solids do not expand much.

Solids Liquids Gases

WHAT HAPPENS WHEN RAILS CONTRACT?

WHAT HAPPENS WHEN A GAS EXPANDS?

Mercury expands when heated. Expansion

joints expand when it is hot.



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WHAT HAPPENS WHEN A GAS EXPANDS?



The rails cool.

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0 10

The particles move more slowly and occupy less space.

The volume decreases, and the rails contract.

0 10



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WHAT HAPPENS WHEN RAILS CONTRACT?



Gases

When gas expands, the volume increases. This can push a cork out.

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Changes of state

SOLID

LIQUID

GAS

mel

ting

solid

ifcat

ion

sublimation

desublimation

evaporation

condensation

endothermic

exothermic

Heat changes can be:

When a state of matter gains or loses heat, it undergoes a change.



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Conduction

Direction of heat

The kinetic energy of the particles increases.

particles of a solid

This is the transfer of heat in most solids.

Heat is transferred

by direct contact.



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Conductors and insulators

metal

Insulators do not allow heat to move through them easily. plastic Double-glazed window

air

air space

cork

Conductors allow heat to move through them easily.



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Convection

gas particles

liquid particles

convection currents

This is the transfer of heat in liquids and gases.

Heat is transferred by the movement of currents.



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Greenhouse

Radiation

solar radiation

radiation emitted by plants

This is the transfer of heat by electromagnetic waves.

No contact is necessary between the source and the heated substance.



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Links

How is heat transferredhttp://antonine-education.co.uk/Physics_GCSE/Unit_1/Topic_1/topic_1_how_is_heat_transferred.htm

Heat transfer activitieshttp://www.reachoutmichigan.org/funexperiments/agesubject/lessons/caps/htransfer.html

Transfer of thermal energyhttp://www.bbc.co.uk/schools/ks3bitesize/science/physics/energy_transfer_4.shtml

Heathttp://www.leavingcert.net/skoool/examcentre_jc.asp?id=4091

Hands-on physics: Heat & temperaturehttp://hop.concord.org/h1/phys/h1p.html

Thermodynamicshttp://www.arborsci.com/CoolStuff/cool26.htm

Solids, liquids and gases and the particle theoryhttp://www.worsleyschool.net/science/files/state/changes.html

Heat and temperaturehttp://coolcosmos.ipac.caltech.edu//cosmic_classroom/light_lessons/thermal/index.html