# Physics -Unit 1.

• Created by: lou
• Created on: 25-05-15 14:38
What are the three ways heat is transferred??
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Conduction and convection involve the transfer of energy by??
Particles.
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Conduction is the main form of heat transer in??
Solids.
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Convection is the main form of heat transfer in??
Liquids and gases.
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The bigger the temperature difference between a body an its surroundings, x energy is transfered by heating.
X = Faster.
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Where is infrared radiation emitted from??
The surface of an object.
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What does an object that's hotter than its surroundings do??
Emits more radiation than it absorbs (as it cools down.).
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What does an object that's cooler than its surroundings do??
Absorbs more radiation than it emits (as it warms up.).
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Why does radiation depend on the surface colour and texture of an object??
Because - Dark, matt surfaces aborb infrared radiation much better than light shinny surfaces such as gloss white/silver. They also emit much more infrared.
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What do light and shiny surfaces do ??
They reflect a lot of the infrared radiation.
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What does the kinetic theory explain??
The three states of matter.
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How are solids explained in the kinetic theory??
Stronger forces of attraction hold the particles close together in a fixed regular arrangement. The particles dont have much energy so they can only vibrate about their fixed positions.
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How are liquids explained in the kinetic theory??
There are weaker forces of attraction between the particles. The particles are close together, but can move past each other, and form irregular arrangments. They have more energy than particles in solids. They move in random directions at low speeds.
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How are gases explained in the kinetic theory??
There are almost no forces of attraction between the particles. The particles have more energy than those in liquids and solids. They are free to move, and travel in random directions and at high speeds.
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What happens when you heat a substance??
You give its paricles more kinetic energy - they vibrate or move faster. This what eventually causes solids to melt and liquids to boil.
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What is conduction??
Conduction of heat energy is the process where vibrating particles pass on their extra kinetic energy to neighbouring particles.
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Why are metals good conductors??
Electrons are free to move inside metals. Hot end electrons move faster collide with free electrons, transferring energy These other electrons pass their energy to other electrons etc. Because electrons move freely it's a faster way of transferring.
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What is convection??
Convection occurs when the more energetic particles move from the hotter region to the cooler region and take their heat enegy with them.
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Why can't convection happen in solids??
Because the particles can't move.
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What are convection currents all about??
Changes in density.
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What is condensation??
When a gas turns into a liquid.
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Condensation in terms of particles.
Gas cools - particles in gas slow down + lose kinetic energy. The attractive forces between particles pull them closer together.
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What is evaporation??
When a liquid turns into a gas.
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Evaportaion in terms of particles.
Particles escape from a liquid. Particles near the surface of a liquid can escape if they are travelling in the right direction and the have enough energy to escape. When the particles escape the ke and as of the remaing particles decreases + cools.
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The rate of evaporation will be higher if the....
Temperature is higher-average particle energy will be higher so more particles have enough energy to escape. Density is lower-forces will be weaker. Surface area is larger-more will be near enough.Airflow over the liquid is greater.
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The rate of condensation will be faster if the....
Temperature of the gas is lower-particles slowdown and form clumps. Airflow is less-concentraion of the substance is higher. Temperature of the surface the gas touches is lower. Density is higher - forces of attraction stronger.
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## Other cards in this set

### Card 3

#### Front

Conduction and convection involve the transfer of energy by??

### Card 4

#### Front

Conduction is the main form of heat transer in??

### Card 5

#### Front

Convection is the main form of heat transfer in??