Area of study 1: Chapters 1/2 (heating processes/moving heat around) Flashcards
What is heat?
The transfer of thermal energy from a hotter body to a colder one
What is internal energy
the total amt of kinetic and potential energy of the particles
What can heat result in?
- increase in temp - net gain of kinetic energy
- state change - potential energy increased
- expansion of object - potential energy increased
What occurs at absolute zero?
particles stop moving at -273 celsius
K ➡️ C?
-273
C ➡️ K?
+273
What is specific heat capacity?
it is the amount of energy required to raise 1kg of the substance by 1C
Higher heat capacity?
= greater amt of energy to raise temp. absorbs a lot more heat before it actually begins to get hot
What is latent heat?
energy released/absorbed during a phase change
difference between fusion and vaporisation latent heat
fusion = melting = energy added so temp increase (solid - liquid)
vaporisation = boiling (liquid - gas)
when a substance is undergoing phase change, why does the temperature not increase?
instead of temp increase, the energy increases the potential energy of the particles, reducing the interparticle forces - extra energy is used in reducing forces btw particles
What is evaporation?
the changing of a liquid into vapour at a temp under boiling point
How does evaporation occur?
if the liquid particles have sufficient energy, they can escape through the surface of the liquid into the air. the higher energy particles escape leaving the lower-energy particles behind which results in the overall kinetic energy decreasing
Evaporation occurs faster in what type of liquids?
volatile ones - such as perfume. the surface bonds are weaker
how does sweating work?
the skin is hot due to work done by it. when one sweats, the energy from the skin is transferred onto the sweat particles, resulting in those heating up. this then results in the higher energy particles to escape, decreasing the temp
Dogs don’t sweat like humans do, after exercising they pant to cool down. When dogs pant they stick out their wet tongue and blow air over it. Explain how the action of panting helps the dog cool down.
- air passing by increases rate of evaporation
- dog is hot (heat) - heats up particles
- saliva heats up, takes that heat from dog which evaporates
- this cools down dog by removing heat
how can evaporation be increased?
- volatility of substance
- surface area: greater area exposed to air
- temp: hotter substance evaporate quicker
- air movement: breeze blowing over increases evaporation
where is evaporation decreased?
humid places
what things influences a change in temp:
- mass
- material
- amt of energy transferred
what is work?
energy transferred by the action of force
conduction is?
the transfer of heat energy through a substance by particle collision with no net movement of particles.
convection is?
the transfer of heat energy by bulk movement of particles.
radiation is?
is the transfer of energy without a medium.
methods of conduction?
- collision of atoms
- delocalised electrons
how does conduction occur through collision of atoms?
in a solid, particles are constantly vibrating. when heated up, the particles vibrate more and these interactions pass on the kinetic energy.
its slow
how does conduction occur through delocalised electrons?
when heated, the cations and electrons gain energy. electrons provide a means by which energy can be transferred quickly
what affects thermal conductivity?
- surface area: greater surface area relative to volume = higher rate of conduction
- temp diff: greater diff between two substances = quicker energy transfer
how does convection work?
- transfer of heat energy by bulk movement of particles
- the cooler, more dense water at the top sinks
- the warm, less dense water at the bottom is displaced upward by it
how to stop convection?
to stop, heat from the top
What is a sea breeze?
occurs at day.
1. both sea and land are warmed
2. warm air from land rises
3. rising air helps form clouds
4. cooler air sinks
5. sea breeze
what is land breeze?
breeze from land towards sea. formed at night when sea and land lose heat. land specific heat capacity is lower, loses heat quicker than sea. sea it warmer, sends air up, cool air sinks, land breeze.
example of conduction?
heat transfer from coffee cup to hand
example of convection?
steaming cold milk to make coffee - kettle
example of radiation?
sunlight - microwave
3 ways interactions with radiation can occur:
- emit radiation
- absorb
- transmit
higher temp of object =? (radiation)
higher temp = higher frequency = shorter wavelength
what affects the emission and absorption of radiation?
- surface area: larger surface area = more
- temp - greater temp diff = more
- surface colour/texture - black surfaces emit radiant heat faster than a shiny/light one
