Physics- Thermal physics

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  • Created by: Kitsune
  • Created on: 06-03-17 06:03
Why does evaporation makes things cooler?
Because the particles that are left have less energy
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Which particles evaporate first?
Once that have more energy
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Why do particles stay close together?
Because there are attractive forces between them
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In terms of speed, what is the difference between boiling and evaporation?
Boiling is faster
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Are bubbles formed when a liquid evaporates?
No
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At what temperature can evaporation occur?
Below the boiling point
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How do you increase evaporation?
Increase surface area, increase temperature, blow fresh air over the liquid
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How is pressure caused?
By particles striking walls of container and chaining momentum
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What is the Boyle's law
The volume of a fixed mass of gas is inversely proportional to its pressure when the temperature is constant
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Why does Boyle's law work only when the gas is cool?
Because at higher temperatures gases expand
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What is thermal equilibrium?
When energy isn't transferred between two objects
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What is internal energy?
The total energy of all the particles in a body
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What is temperature?
The measure of the average kinetic energy of an individual particle
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Why is mercury used in thermometers?
Because it expands at a steady rate
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When is a scale said to be linear?
When it is divided into equal parts
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How can a thermometer be made more sensitive?
It can be made thinner
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What does calibrated mean?
Given a scale
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Why does mercury rise in a thermometer?
It expands when it is heated
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What is a thermistor?
A resistor whose resistance changes by a large amount over a narrow temperature range
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Does a resistance of a thermistor change in a linear way?
No
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Why do you need to carefully choose a thermistor for a given temperature?
Because its resistance will change significantly only over a very small range
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What does a thermocouple do?
It gives an output voltage that depends on the temperature
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What is the structure of a thermocouple?
It is made out of pieces of wire from two different metals. Wire of metal x is joined at each end to the wire of metal y, frying two junctions
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How does a thermocouple work?
One junction is placed in ice at 0 degrees and the other junction is placed on an object whose temperature is to be measured. The voltmeter shows the reading that is caused by the temperature change.
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In a thermocouple, the higher the temperature...
The higher the voltage
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Why do they heat ups and cool down quickly?
Because they are small
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Why are they useful for measuring rapidly varying temperature?
They are small
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What is thermal expansion?
When substances expand when heated.
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What are the uses of thermal expansion?
Heating a lid to open a bottle, fitting tires on wheels
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Why are bridges made in sections?
Because during the summer the bridge may buckle
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In what state is expansion fastest?
Gas
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Why is expansion slower in solids than in liquids?
It's hard for the particles in a solid to push each other as far as they could in a liquid
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What is thermal capacity?
The amount of energy body can store as it is heated up
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What is specific heat capacity?
The energy required per kilogram and per degree celsius to raise the temperature of a substance
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What is the specific latent heat of vaporisation?
The energy per kilogram required to cause a substance to change state from liquid to gas at its boiling point
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What is the specific latent heat of fusion?
The energy per kilogram required to cause a substance to change state from solid to liquid at its melting point
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What does thermal energy require to be transmitted?
A temperature difference
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Why do we think that a metallic spoon is cool when we touch it?
When our finger touches the spoon heat is lost from the finger because metals are conductors.
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How does convection work in gases?
Hot air expands, becomes less dense and rises above the cold air.
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What is a convection current?
A movement of a fluid that carries energy from a warmer place to a colder one
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What is the difference between convection and conduction?
In conduction the energy is transferred without the material itself moving but in convection the energy is transferred by the movement of material itself
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Why are some materials poor conductors?
Because in them particles can only vibrate and pass on those vibrations
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How does light travel through space?
By electromagnetic radiation
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What radiation do hot objects produce?
Infrared radiation
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What surfaces are the best reflectors and the worst absorbers?
Shiny white
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What surfaces are the best absorbers and the worst reflectors?
Matt black
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What surfaces are the best emitters?
Matt black
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What two factors affect the rate of radiation?
Temperature of the surface and the surface area
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How can you keep an object warm?
Insulate it
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Why is there a vacuum between glass frames in windows?
So that heat can escape only by radiation
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In a thermos, what is done to the gap between two glass walls?
It is evacuated so no convection can occur
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How is radiation prevented in a thermos?
The inner side of the glass wall is covered with silver
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Other cards in this set

Card 2

Front

Which particles evaporate first?

Back

Once that have more energy

Card 3

Front

Why do particles stay close together?

Back

Preview of the front of card 3

Card 4

Front

In terms of speed, what is the difference between boiling and evaporation?

Back

Preview of the front of card 4

Card 5

Front

Are bubbles formed when a liquid evaporates?

Back

Preview of the front of card 5
View more cards

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