Physics #1 - Heating and Cooling

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  • Created by: megan-jt
  • Created on: 29-10-15 15:26
Heat can be transferred from place to place by what three methods?
Conduction, Convection and Radiation
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Dark matt surfaces are better/worse at absorbing heat energy than light shiny surfaces.
Better
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What do all objects emit and absorb?
Infrared/Thermal Radiation
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Finish- The hotter the object....
the more infrared radiation it emits
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Infrared radiation is a type of what?
Electromagnetic radiation, it travels through waves not particles and so can pass through a vacuum
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Use the kinetic theory to describe and explain a solid's particles arrangement and movement?
Close together, regular pattern, vibrate around a fixed point.
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Use the kinetic theory to describe and explain a liquid's particles arrangement and movement?
Close together, randomly arranged, move around each other.
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Use the kinetic theory to describe and explain a gases particles arrangement and movement?
Far apart, random, move around quickly in any direction.
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Why cant solids flow?
The particles cannnot move from place to place.
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What can't solids be compressed/squashed?
The particles are close together and have no space to move into.
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Why can liquids flow?
The particles can move around each other.
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Why can't liquids be compressed or squashed?
The particles are close together and have no space to move into
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Why can gases flow?
The particles can move quickly in all directions?
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Why can gases be compressed or squashed?
Particles are far apart and have space to move into.
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What can conduct?
Metals
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What cant conduct and what are they called?
Gases, non-metals, they are called insulators
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Explain conduction in metals?
The electrons in metal can leave their atoms and move (free electrons) leaving the metal charged (loss of electrons) making them ions. These ions then vibrate constantly and transfer the heat, hot to cold. Kinetic energy is passed by free electrons.
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What does convection occur in?
Liquids and gases
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How does convection occur?
when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.
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Choose the correct word: gases and liquids contract/fall/expand when heated?
Expand
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In gases and liquids when heated what do the particles do?
Move faster and take up more volume
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Why do gases and liquids take up more volume when heated?
The gap between the particles widens
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Explain a convection current?
The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas.
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What's evaporation?
liquid changing to a gas
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What's condensation?
gas changing to a liquid
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Explain evaporation?
The particles in a liquid have different energies. Some will have enough energy to escape from the liquid and become a gas. The remaining particles in the liquid have a lower average kinetic energy than before
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Explain condensation?
The particles in a gas have different energies. Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down. They come close together and bonds form between them. Energy is released when this happens.
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Factors affecting the rate of evaporation?
Evaporation increases as the temperature of the liquid is increased, it also increases as the surface area increases or a draught is across the top
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Factors affecting the rate of condensation?
Condensation increases as the temperature of the gas decreases,
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The bigger the temperature difference (between object and surroundings) the...
quicker the rate of heat loss
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The bigger the surface area the...
quicker the rate of heat loss
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What is the problem with elephants large volume?
Elephants live in hot climates and due to it having a large volume low surface area the rate of rate loss is slow and takes a long time to lose heat, this could mean the elephant might overheat.
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How have elephants adapted to solve the large volume issue?
They have adapted by having large, thi ears which mean that the rate of heat loss is quick and the elephants don't overheat.
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Engineering and heat loss, name a product that displays this?
Products such as the radiator are designed so that they are thin, big and have a large surface area, meaning that heat loss is quicker so it heats the room quicker.
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What's a U-value?
U-values measure the effectiveness of a material as an insulator in buildings.
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The lower the U-Value the...
the better the heat insulator
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What does the specific heat capacity allow us to calculate?
The amount of energy needed to heat up an object.
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What's payback time and the equation for it?
How cost-effective something is, so will it 'pay for itself' over time? Equation: cost of installation (£) ÷ savings per year in fuel costs (£)
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What do solar panels do?
Heat up water from sun radiation generated, found on the roof
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Advantages of solar panels?
Renewable energy source, no harmful polluting gases are formed
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Disadvantages of solar panels?
Really expensive to install, don't work at night or in cool climates (UK)
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Whats the difference between temperature and heat?
Temperature is a measure of how hot something is. Heat is a measure of the thermal energy contained in an object. Temperature is measured in °C, and heat is measured in J
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When heat energy is transferred to an object name three ways the temperature might increase?
1.) The mass of the object 2.) substance the object is made from 3.) The amount of energy transferred.
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What is specific heat capacity?
the amount of energy needed to change the temperature of 1 kg of the substance by 1°C.
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Equation of how to calculate energy transfer?
E = m x c x 0 (theta not 0)
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E = m x c x 0, what do they stand for and their units?
E is the energy transferred in joules, J m is the mass of the substances in kg c is the specific heat capacity in J / kg °C θ (‘theta’) is the temperature change in degrees Celsius, °C
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Card 2

Front

Dark matt surfaces are better/worse at absorbing heat energy than light shiny surfaces.

Back

Better

Card 3

Front

What do all objects emit and absorb?

Back

Preview of the front of card 3

Card 4

Front

Finish- The hotter the object....

Back

Preview of the front of card 4

Card 5

Front

Infrared radiation is a type of what?

Back

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