P6 Molecules And Matter Flashcards

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1
Q

Which two quantities do you need to measure to find the density of a solid or liquid?

A

mass and volume

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2
Q

What happens to the particles in a substance if its temperature is increased?

A

they move faster and the energy in their kinetic energy store increases

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3
Q

Why are changes of state physical changes?

A

no new substances are produced and the substance will have the same properties as before if the change
is reversed

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4
Q

Why is the mass of a substance conserved when it changes state?

A

the number of particles does not change

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5
Q

What is the internal energy of a substance?

A

the total kinetic energy and potential energy of all the particles in the substance

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6
Q

Why does a graph showing the change in temperature as a substance cools have a flat section when the substance is changing state?

A

the energy transferred during a change in state causes a change in the internal energy of the substance

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7
Q

What is the name given to the energy transferred when a substance changes state?

A

latent heat

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8
Q

What is the specific latent heat of a substance?

A

the energy required to change the state of one kilogram of that substance with no change in temperature

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9
Q

What is the specific latent heat of fusion of a substance?

A

the energy required to change one kilogram of the substance from solid to liquid at its melting point, without changing its temperature

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10
Q

What is the specific latent heat of vaporisation of a substance?

A

the energy required to change one kilogram of the substance from liquid to vapour at its boiling point, without changing its temperature

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11
Q

On a graph of temperature against time for a substance being heated up or cooled down, what do the flat (horizontal) sections show?

A

the time when the substance is changing state and the temperature is not changing

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12
Q

What property of a gas is related to the average kinetic energy of its particles?

A

temperature

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13
Q

What causes the pressure of a gas on a surface?

A

the force of the gas particles hitting the surface

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14
Q

Give two reasons why the pressure of a gas in a sealed container increases if its temperature is increased.

A

the molecules move faster so they hit the surfaces with more force and the number of impacts per second increases, so the total force of the impacts increases

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15
Q

Give two reasons why the temperature of a gas increases if it is compressed quickly.

A

the force applied to compress the gas results in work being done to the gas, and the energy gained by the gas is not transferred quickly enough to the surroundings

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16
Q

Explain why the pressure of a fixed mass of gas decreases if the volume is increased and kept at constant temperature.

A

the distance the particles travel between each impact with a wall of the container is greater, so the number of impacts per second decreases, so the total force of the impacts decreases