Zusammenfassung der Ressource
Heat Transfer and Kinetic Theory
- Infrared Radiation
- Infrared radiation transfers heat energy
- Dark, matt surfaces are
best at absorbing and
emitting infrared
radiation
- Light, shiny surfaces are
worst at absorbing and
emitting infrared radiation
and reflect a lot of the
radiation
- If an object is cooler than its
surroundings it will absorb more
infrared radiation than it emits
- If an object is warmer
than its surroundings it
will emit more infrared
radiation than it absorbs
- Everything absorbs and emits
infrared radiation
- Kinetic Theory
- Gases
- Almost no forces of attraction
- Particles move in a random direction at high speeds
- High energy levels
- Solids
- Strong forces of
attraction keep it in a
fixed pattern
- Low amount of
energy so it can
only vibrate in
fixed positions
- Liquids
- Weak forces of attraction
- The particles can move in random directions at low speeds
- Conduction
- A type of heat
transfer that
occurs mainly
in solids but
also in liquids
and gases
- The particles vibrate and transfer
their heat energy to neighbouring
particles
- More dense materials are
better conductors because their
particles are closer together
- Materials that have
particles that are
far apart transfer
heat via conduction
slower and are
known as insulators
- Metals are good conductors because
they contain free electrons which allows
them to transfer energy faster
- Convection
- Occurs mainly in liquids and gases
- Particles vibrate more as they
heat up and so take up less
space and become less dense
- Less dense
particles rise
taking the energy
with them
- Convection currents
occur when the less
dense particles rise
and are replaced by
the denser particles
- Condensation
- Condensation is the process of turning a gas into a liquid
- If particles lose energy they slow down and the attractive
forces between them grow stronger and if the forces are
strong enough the particles join and become a liquid
- Factors affecting the rate of condensation
- Temperature of the surface the gas touches
- Airflow
- Density of gas
- Temperature of the gas
- Evaporation
- Evaporation is the process of a liquid turning into a gas
- If the particles have enough
energy and are travelling in the
right direction they can escape the
attractive forces of the other
particles and evaporate
- Factors affecting the rate of evaporation
- Airflow over the liquid
- Surface area of the liquid
- Temperature of the liquid
- Density of the liquid
- Rate of Heat Transfer
- Factors affecting rate of heat transfer
- Surface Area
- Type of material
- Colour
- Surface area to volume ratio
- The smaller this is, the faster the transfer
- Controlling Heat Transfer
- Vacuum Flask
- The flask uses two walls to create a
vacuum to stop heat loss through
conduction and convection
- The flask walls are silver and
shiny to stop heat loss through
radiation
- The insulated support stops the
flask walls from cracking under
the pressure and minimises heat
loss from conduction
- The stopper is made of plastic and filled with cork and
foam to reduce heat loss through conduction
- Humans and Animals
- Hairs on your skin
stand up to trap a
thicker layer of
insulating air to limit
heat transfer by
convection
- Blood is diverted to
the surface where
heat can be lost as
radiation resulting in
pinker skin tone
- Arctic foxes have small ears to minimise heat loss via radiation
- Desert foxes have large ears to maximise heat loss via radiation