58606584 Science Form1 Chapter 7
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Transcript of 58606584 Science Form1 Chapter 7
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Chapter 7HEAT
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7.1 Heat as a form of energy
Heat is ________________. The SI unit is __________
When heat energy is supplied to a substance, the _______________
of the substance will _________.
Heat flows from a _________ to a _______ place. This process of
heat transfer will stop when the temperature of the 2 places
become _____________.
Sources of heat:
Burning
Friction
Electricity
The mantle of the Earth
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Use of heat:
drying
ironing
cooking
keeping warm
Temperature Temperature is the________________ of hotness or coldness of an object.
A thermometer is used to measure temperature. The SI unit of temperature
is the _________________ However, the commonly used unit is
______________
__________ substances have ____________________ whereas ________
substances have ____________________ .
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4) The difference between heat and temperature:
Heat
A form of energy
Can do work
SI unit = Joule (J)
Temperature
A measure of the
hotness or coldness ofan object
Cannot do work
SI unit = kelvin (K)
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5) 3 types of thermometers:
Type ofthermometer
Mercuryin glass
laboratorythermometer
Clinicalthermometer
Alcoholin glassthermometer
Rangetemperature
-10 0C and 110 0C
35 0C and 42 0C
-117 0C and 78 0C
Use
Measures
temperature whendoing experiments
Measures bodytemperature
Measures very lowtemperatures
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Is heated
Particles _______ heat
Particles receive energyand move_______
The distance betweenthe particles _______
The volumeof thematter _______
The matter _______
Is cooled
Particles _______ heat
The particles lose energyand move more_______
The distance betweenthe particles _______
The volumeof the matter_______
The matter _______
Matter7.2 The effectof heat flow
on matter
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Expansion and Contraction (Solids)
1) A solid _______ when it is heated. It _______ when it is cooled.
2)The expansion of solid can be shown by a metal ball.
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3) Different metals expand at different rates:
Aluminium
Brass expansion
increases
Copper
Iron
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4) Different metals expand unequally when heated to the sametemperature. This can be explained by heating ______________
Brass
Iron
Heated
* When heated, showing that ________ expands more than ______
Heated
* When heated, showing that __________expands more than__________
Aluminium
Copper
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Expansion and Contraction (Liquids)
1) A liquid _______ when it is heated. It _______ when it is
cooled.
2) Different liquids expands and contract at difference rates
Benzene
Alcohol
increases
Water expand
Mercury
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Expansion and Contraction (gases)
Gases _______ when it is heated and _______ when cooled.
Different gases expands at the same rate.
Transfer of Heat
Heat can be transferred from a hot to a cold place by theprocess of
a) Conduction
b) Convection
c) Radiation
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CONDUCTION
1) Conductionis the transfer of heat energy between neighboring
molecules in a substance. It takes place from a region of
___________________to a region of ________________________________________________
2) When one part of an object is heated, its get hot. The particles there
gain heat energy making them vibrate stronger. They then collide and
pass some heat energy to the neighbouring particles.
Iron rod
Heat transfer
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CONVECTION
1) Convection is the transfer of heat in fluids (liquids and gases) carried
out by moving particles.
2)______fluidsbecome less dense and move upwards.
______fluidsthat are densermove down to replace the hot fluids.
3) A convection current is produced.
Convection in liquid
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RADIATION
Radiation is the transfer of heat without involving a medium.
Radiation can take place through air space or a____________.
Radiation heat moves at the speed of_________.
Radiation heat can be absorbedor reflected
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Conduction
Solid
Heat is transferfrom particle toparticle through
vibration
Convection
Fluid (liquid orgas)
Heat is broughtby the heatedparticles that
move upwards
Radiation
Solid, liquid or gas/ no medium
Heat moves in theform of waves in a
straight line
Comparison between conduction,
convection and radiation
Medium
Take place inVacuum
Speed
Way heat istransfer
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2) SEA BREEZE
Sea breeze blow during the______.
During the day, the______heats up faster than the______.
The air on surface of the land become warm(less dense) and______
The cooler air over the sea (denser)______in to take place of the
warm air.
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HEAT CONDUCTOR
Substance that conduct heat are called __________________.
Some substances conduct heat readily(good heat conductor)
All metal such as iron, magnesium, aluminium and zinc are good
____________of heat.
Copper
Aluminium
Brass best conductor
Zinc
TinIron
Lead
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Uses of heat conductors
Cooking utensil ( kettles, pots, pans) aremade from metals. Food can be cooked
quickly or water can be boiled quickly.
Mercury in the bulb expands
and contracts easily.
The bottom of an electric iron is
made up of metals so that it can
heat up quickly
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HEAT INSULATOR
Substance that conduct heat poorly are called insulators
Non-metal such as glass, wood, cork, air, water and wool are insulators.
Fluids (liquid, gas) are poor conductors of heat.
Uses of heat insulators.
Handles of kettles, irons and
cooking utensils such as pots andfrying pan are made of wood
or plastic
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Application of the principle of convectionin daily life
Ventilation of building
a. The hot air in the building will flow out through theventilation holes at the top.
b. The cold air enters through the holes (windows/door) on the lowerpart.
2) Refrigerator
a) Cold air from the freezer compartment at the top moves downto the lower part of the refrigerators. The hot air is moved up.
3) The cooling system in a car(radiator of the car)a) The water around the engine becomes hot when the engine
moves. Hot water flows up through the radiator and getscooled. The cold water moves down and flows back around theengine.
7 3 Eff t f H t M tt
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7.3 Effect of Heat on Matter
1) Matter exists in solids, liquids and gases. Matter can change from one
state to another.Eg: Solidcan be change to a liquidby heating. (heat absorb)
A liquidstate can be change to a solidby cooling. (heat release)
Sublimation
Sublimation
Liquid
GasSolid
e c ange n e s a e o
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e c ange n e s a e omatter.
Process
Condensation
Melting
Freezing
Evaporation/Boiling
Sublimation
Sublimation
Change in stateAbsorb/ release
heat
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CHANGE IN STATE OF MATTER DAILY LIFE
1) Wet clotheswhen wet clothes dry in the sun, the water in the
clothes evaporate. 2) Puddles of water - After a rain, there are puddles of water on the
ground. When the sun come out, these puddles
evaporate.
3) Ice cubes
Ice cube can be prepared by freezing water under lowtemperature.
4) Moth ballMoth ball become smaller because of the process of
sublimation.
5) Rainwater - Water vapours in clouds condense to form rainwater.
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7.5 : Absorbing and Giving Out Heat
Good heat absorberand emitter
Bad heat absorberand emitter