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Slide 1

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Physics Unit 1 revision…read more

Slide 2

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Infrared Radiation
Infrared radiation- all objects emit and absorb,
the hotter the object the more IR given out, the
bigger the temperature difference the faster the
heat is transferred
Dark, matt surfaces good absorbers and
Light, shiny surfaces bad absorbers and
emitters but good at reflecting heat away from
Radiation from the sun is absorbed by the black
surfaces to heat the water in pipes…read more

Slide 3

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Kinetic theory
Solid- fixed particles vibrate around a fixed point,
they're closed together so aren't easily
compressed, little kinetic energy, strong forces of
attraction, high density.
Liquids- weaker forces between the particles,
particles are close together but can move past
each other, more kinetic energy, but has a fixed
Gases- no forces of attraction therefore there are
lots of spaces between the gases so can be easily
compressed. Free to move around with no fixed
volume- high kinetic energy…read more

Slide 4

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Solids- solids are good conductors due to the particles being
closed together, heat energy is transferred by kinetic energy.
When the particles are heated they increase in kinetic energy
and pass on the vibrations by banging into each other.
Materials with large gaps between materials are poor
conductors but are good insulators e.g. air
Metals- metals are even better conductors due to having free
electrons which are free to move so when the metals are
heated they gain kinetic energy causing free electrons to
gain kinetic energy and diffuse across the metal lattice,
colliding with other free electrons so the energy is transferred
faster.…read more

Slide 5

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The particle is heated so becomes less dense and spread out, then it
rises. When the warm particles rise it displaces the cooler more dense
particle which sink to the heating source.
· When a gas cools the particles lose kinetic energy, the attractive forces
between the particles pull them closer together and when the temperature
is cool enough it condenses- factors make it faster:
Temperature of the surface gas touches is lower, Density is higher
Surface area of the surface the gas touches is larger, Airflow is less
· When particles escape the from a liquid, particles near the surface can
become a gas if the particles are travelling in the right direction to escape
and if the particles have enough energy to break free from the other
particles in the liquid. Particles that have the most energy leave the liquid,
so the average temperature of the liquid decreases- creates a cooling
effect- factors make it faster: temperature is higher, density of liquid is
lower, higher surface area of the liquid, higher airflow over it.…read more

Slide 6

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Rate of heat transfer
Surface area and volume
Heat is radiated from the surface of an object, the
bigger the surface area the more infrared waves
can be emitted from the surface. Radiators have
large surface area to increase the amount of heat
they transfer. If the same temperature have the
same surface area but different volumes, the
smaller volume will cool quicker as a higher
proportion of the object will be in contact with its
surroundings.…read more

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