Flashcards
Heating Up and Down
Cards in this deck (21)
- 1Heating Up and DownPhysics 1a 5.1 - 5.4
- 2What is condensation?When a gas cools, the particles in the gas slow down and lose kinetic energy. The attractive forces become greater, the gas becomes a liquid when condensation occurs. Water vapour in the air condense when it comes into contact with a cold surface.
- 3What is evaporation?When particles from a liquid escape the surface, they can escape at temperatures much lower than the liquid's boiling temperature.
- 4Under what circumstances can particles near the surface of the water escape?1) They must be travelling in the right direction.
2) They must be travelling fast enough to overcome the attractive forces of the other particles in the liquid. - 5Which particles are most likely to evaporate?Whose which are travelling the fastest, with the most kinetic energy - so when they do, the average speed and kinetic energy of the remaining particles decreases.
- 6How does the temperature of an evaporating liquid decrease?The average particle energy has decreased - therefore the liquid cools. This is useful in the process of homoeostasis, as the sweat on your skin evaporates.
- 7In which conditions will the rate of evaporation be greater?1) Higher temperature - average particle energy is higher, more can escape.
2) Lower density - forces between particles will be weaker, more have enough energy.
3) Larger surface area - more at surface.
4) Airflow over the liquid is greater - the air is replace more regularly therefore the concentration of evaporating substance in the air remains lower. - 8In what conditions will the rate of condensation be greater?1) Lower temperature - average particle energy is lower so more will clump together and form droplets.
2) Airflow is less - higher concentration in the air therefore more condensation.
3) Lower temperature of the surface.
4) Higher density - stronger attractive forces between particles, fewer particles have the energy to overcome these. - 9How does surface area affect the amount of heat energy radiated?The greater the surface area, the more infra-red waves radiated - therefore the rate of heat transfer is greater.
- 10Why do car engines have 'fins'?To increase the surface area so that heat is radiated away quickly, and the engine cools quicker.
- 11How do heat sinks work?These devices are designed to transfer heat away from objects they're in contact with, they have fins to create a large surface area so that heat emission is quicker. They are used in computer components.
- 12Which object would cool quicker if two object were at the same temperature, and have the same surface area but different volumes?The smaller object - as a higher proportion of the object will be in contact with the surroundings.
- 13What other feature can affect the rate of heat transfer?The material, good conductors transfer heat more quickly than insulating materials, it also matters whether the material is in contact with conductors or insulators. Heat will be conducted away much faster if it is in contact with a conductor.
- 14How is a vacuum flask designed to limit heat transfer?The glass bottle is double-walled with a vacuum between them, this stops all conduction and convection. The walls either side of the vacuum are silvered to minimise heat transfer by radiation. Insulated foam supports the bottle which reduces heat conduction to or from the outer glass. The stopper is made of plastic and filled with cork or foam to reduce heat conduction through it.
- 15How is the human body adapted to keep you warm when it is too cold?Your hairs stand up to trap a thicker layer of insulating air around the body, this limits heat loss through convection.
- 16How is the human body adapted to keep you cool when it is too hot?More blood is diverted to the surface of your skin so that more heat can be lost through radiation - that's why you go pink when you're hot.
- 17What do some animals have to keep them cool/warm in extreme climates?Animals in colder climates generally have smaller ears with a smaller surface area to reduce heat loss by radiations. Whilst those in a hotter climate have larger ears with a larger surface area to allow heat loss through radiation.
- 18What is specific heat capacity?The amount of energy needed to raise the temperature of 1kg of a substance by 1 degree C.
Eg. the specific heat capacity of water is 4200J/kg degrees C. - 19What is the equation of specific heat capacity?E = m x c x θ
E is energy transferred (J)
m is mass (kg)
c is specific heat capacity (J/kg degrees C)
θ is temperature change (degrees C) - 20Why do heaters have a high heat capacity?This means that they can store a lot of energy.
- 21Explain how heaters work.Water has a very high SHC, and it is also a liquid therefore it can be pumper around in pipes - electrical storage heaters are designed to store heat energy at night (when electricity is cheaper), and then releases it during the day. The heat is stored in bricks or concrete which have a high heat capacity also.
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- Flashcards on Heating Up and Down, created by Lauren Adams on 16/04/2016.
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- Lauren Adams
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