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Heat
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Form of energy
Flow of energy from warmer to cooler matter
Matter = liquid, solid, gas
An object feels warm when it is warmer than ________________
Heat transfer between objects is done through
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Convection
Conduction
Radiation
Matter – States of Matter
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Liquid – fixed volume but takes on the shape of the container
Solid – fixed shape and volume; atoms in a regular arrangement, does not take on the
shape of the container
Gas – assumes the shape and volume of the container
Change of State of Matter: the state of matter may change with the addition or removal of
thermal energy (heat)
e.g. ice (add heat) > liquid (add heat) > gas (remove heat) > liquid (remove heat) > gas
Heat Energy: how active the atoms and molecules are
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Hot: atoms and molecules are excited – rapid movement
Cold: less excited – less movement (ref. food colouring experiment)
Thermal Expansion – Changes in Volume (space)
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Hot – same mass, greater volume
Cooler – same mass, less volume (ref. balloon demo and 2L bottle demo)
Thermal Equilibrium – low energy meets high energy
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Ice cubes and hot water demo – hot water loses energy to cool ice >> warm water
Types of Heat Transfer
Radiation – warm or hot matter emits heat that is then absorbed at a distance without
touching the object
e.g. sun’s light energy is absorbed by Earth’s water, rocks, and soil, which changes to heat >> it
warms the layer of air closest to Earth’s surface >> reason why the temperature is warmer
closer to Earth than at the top of a mountain
Convection
Movement of thermal energy from one area to another through liquid or gas
Heat displaces cooler gas or liquid (ref demo lava lamp, demo balloon kettle, demo paper box
kettle),
Question: why are most furnace vents on the floor instead of the ceiling?
Conduction
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Materials are in physical contact
Kinetic (moving) energy in transferred when their molecules collide
Main way for heat to travel through solids
All solids conduct heat but some are better than others (ref spoon experiment)
Good conductors of electricity are usually good conductors of heat (ref steel wool demo)
Styrofoam is a poor conductor but a good insulator – air is a poor conductor, therefore many
porous (full of air holes) materials are good insulators (ref. carpet demo)
Sources of heat
Temperature increases as you go deeper into the Earth
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Molten rock found at depths of 80 – 100 kilometres, at temperatures of 600 – 1200
degrees C
Some of this heat caused by friction of moving tectonic plates >> creates magma
chamber >> rises to the surface >> volcanic eruption
Geysers – underground chambers fill with groundwater and are heated geothermically – water
boils, creating pressure and causing the geyser to erupt (ref. geyser demo)
3 stages of geyser’s cycle
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Heating – depends on the amount of water and amount of geothermal energy present –
water boils and creates steam
Erupting – steam expands to over 1500 times the original volume of water, pushing
water back up the fissure (tube) and out through the top of the hole
Refilling – eruption reduces pressure and allows water to flow back into the chamber –
the cooler water condenses the steam in the fissure
Fire
Oxygen atoms combining with atoms of the substance being burned
External heat source (match) >> excites atoms >>> vibrates >>> oxygen, carbon and hydrogen
flying off in all directions >>>> oxygen combines with loose atoms and molecules >>> on fire!
Fire produces
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Water (H20)
Carbon dioxide (CO2)
Methane
Pentane
Octane
Plus: heat, light, and sound
Piece of burning wood is like a chemical factory
Ignition point is the minimum temperature at which a solid or liquid will catch fire and stay lit
Fire Triangle – need all 3 elements:
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Fuel >>>> Heat >>>> Oxygen
Absence of one of these = no fire
How does a fire extinguisher work?
Measurement of Heat
Old standard – Fahrenheit
Current standard – Celsius
Water changes states
0o – to solid (freezes to ice)
100o – to gas (boils to steam)
Temperature increase by mechanical means:
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By friction between surfaces (ref. ice cube experiment)
By mechanical shock (ref. hammering demo)
By compression of gases (ref. air pump demo)
By stirring (ref. tube demo)
By an object experiencing a fall
Common factor is motion – kinetic energy of objects converted to kinetic energy of particles