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physics > Matter & Particles > Flashcards

Matter & Particles Flashcards

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1
Q

What is the density?

A

Mass per unit volume.
D = M / V.

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2
Q

How can we measure density of solids?

A

Use balance to measure its mass.
Irregular solids – find volume by displacement.
Water displaced by the object – volume in measuring cylinder = volume of object.

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3
Q

How can we measure density of liquids?

A

Play measuring cylinder on balance and zero the balance.
Pour liquid into measuring cylinder – record mass & volume of liquid.

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4
Q

Describe how objects float based on density?

A

Object denser than liquid x doesn’t float.
Object less dense than liquid - floats.

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5
Q

What is pressure?

A

Force per unit area.

Pressure = F / A.

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6
Q

Describe how pressure varies with force?

A

Larger the area force applied over - lower pressure.
E.g, snowshoes spread out weight over larger area - lower pressure.

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7
Q

Describe how pressure beneath a liquid’s surface changes with depth & liquid density?

A

More dense a liquid is - more particles in a space - more particle collisions & greater total force per unit area = higher pressure.

Higher depth of liquid - more particles above - adds to weight = higher pressure.

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8
Q

What is the equation for change in pressure beneath a liquid’s surface?

A

Change in pressure = liquid density * gravity * change in height (m).

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9
Q

Describe the particle model of solids?

A

Fixed, regular arrangement.
Vibrate about fixed points.
Strong forces of attraction between particles

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10
Q

Describe the particle model of liquids?

A

Close together - but particles further than solid.
Irregular arrangements & move past each other.
Weaker forces of attraction than solid.

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11
Q

Describe the particle model of gases?

A

Irregular arrangement.
Almost no forces of attraction between particles.
Particles have higher energy than solids/liquids - move in random directions & high speeds.

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12
Q

What are shapes & flow of solids/liquids/gases?

A

Solids - fixed size & shape.
Liquids/gases can flow - fill the shape of the container.

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13
Q

What are compressibility of solids/liquids/gases?

A

Gases - compressed & solids/liquids can’t.
Gas particles far apart - can be pushed closer together - solids/liquids can’t be pushed closer.

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14
Q

What are volume of solids/liquids/gases?

A

Solids/liquids - fixed volume.
Gases expand - same volume of container.
Strong forces between particles in solids/liquids keep particles close together.

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15
Q

What are density of solids/liquids/gases?

A

Solids > liquids > gases.
Density = mass per unit volume.
Particles closest together in solids so most particles for the same volume = most mass.

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16
Q

What are the changes of state?

A

Solids - Liquid - melting.
Liquid - Solid - freezing.
Liquid - Gases - boiling.
Gases - Liquids - condensation.

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17
Q

What are particles?

A

Atoms/molecules/ions/electrons.

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18
Q

What is absolute 0?

A

0K = -273°C.
Decrease temperature until particles have minimum possible KE & temperature can’t get lower.

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19
Q

Describes the relationship between the motion of particles and temperature?

A

Particles have KE.
Is the higher temperature – more energy in KE.

20
Q

Describe the pressure and changes of pressure in the gas?

A

Random motion of gas particles – collide with container walls – exerting a force.
If the force per unit area exerted by the particles increases – gas pressure increases and if the force decreases then gas pressure decreases.

21
Q

What is evidence for the kinetic particle model of matter?

A

The random motion of microscopic particles in a suspension.

22
Q

How can microscopic particles be moved?

A

By collisions with light, fast–moving molecules.

23
Q

Describe Brownian motion?

A

Microscopic particles of solid suspended in fluid.
Microscopic particles of solid move within fluid – even when fluid isn’t moving.
Microscopic particles move in random directions.

24
Q

Explain Brownian motion?

A

Fluid is made up of many small particles.
Microscopic particles of solid – larger and more massive suspended in fluid – small/fast fluid particles randomly collide with solid particles.
These random collisions change speed and direction of solid particles, which are much larger than fluid particles – moving them in random directions.

25
Q

Describe the effect of higher temperature on a gas?

A

Higher temperature – particles move faster.
Total force exerted on container walls increases because particles collide more often with the walls of the container & they exert a larger force on the container.
So pressure is higher.

26
Q

Describe the effect of decreasing volume on the pressure of a gas?

A

Decreasing volume – particles less room to move.
Particles collide with container walls more often.
So greater overall force exerted on the wall – pressure increases.

27
Q

How can you convert between Kelvin & Celsius?

A

Kelvin temperature = Celsius + 273.

28
Q

What is the equation to find changes in volume and pressure at a constant temperature?

A

pV = constant.
P1V1 = P2V2.

29
Q

Describe the thermal expansion of solids, liquids and gases?

A

When substances are heated, they get bigger.
.

30
Q

Why does thermal expansion happen?

A

Thermal expansion happens because particles in the substance gain energy and move away from each other as the temperature increases

31
Q

Explain – in terms of motion and arrangements of particles, the expansion of solids?

A

Solids have strongest forces between particles – even when particles gain energy – solid particles can’t move very far apart.
Solids, expand the least.

32
Q

Explain – in terms of motion and arrangements of particles, the expansion of liquids?

A

Liquids have weaker forces of attraction between particles and solids – liquid particles can move further apart.
Liquids expand more than solids.

33
Q

Explain – in terms of motion and arrangements of particles, the expansion of gases?

A

Almost no forces of attraction between particles in gas – gas particles can move furthest when they gain energy.
Gases expand the most.

34
Q

Describe some applications of thermal expansion?

A

Heat a metal rod – gets longer and when it cools - gets shorter again.
Rivets use this to secure objects together.
Rivet starts as a very hot metal rod, threaded through holes in the plates.
Rivet then hammered down – ends are flat against surfaces of the plates.
As the rivet cools – length decreases – flattened ends of the rivet, pull two plates together tightly.

35
Q

What is a difficulty of thermal expansion?

A

If an object tries to expand, and can’t – experiences forces that could damage the objects.

36
Q

How do expansion joints work?

A

Fasten pieces of a building together while leaving a small gap where pieces meet.
When building gets hot, it can expand into this gap – without causing damage.

37
Q

Describe melting and boiling?

A

When a substance is changing state – doesn’t change temperature.
Because energy in internal energy store will change – but energy in kinetic energy stores won’t change

38
Q

Describe condensation in terms of particles?

A

Condensation occurs at the boiling point – as a gas is cooled – kinetic energy store decreases.
Once temperature reaches boiling point – gas begins to change state.
Energy continues to be transferred away from the substance – causing particles to move closer together.
Forces between particles become stronger as particles move closer to each other - until liquid formed.

39
Q

Describe solidification in terms of particles?

A

When a liquid being cooled reaches melting point – liquid particles move closer together.
Forces between particles become stronger as they move closer together.
Eventually particles form fixed, regular arrangement – substance has solidified.

40
Q

Describe evaporation?

A

More energetic particles escape from a liquid surface and become gas particles.

41
Q

Describe the differences between evaporation and boiling?

A

In boiling – bubbles of gas form in boiling liquid – which rise to the surface and gas escapes.
Boiling only occurs at boiling point.

Evaporation is when individual particles escape the surface of the liquid and no gas bubbles are formed.
Evaporation occurs at temperatures below the boiling point.

42
Q

What does evaporation cause?

A

Evaporation causes cooling of a liquid.

43
Q

When can particles of the liquid escape the surface?

A

If particles are travelling towards the surface.
If they have enough kinetic energy to overcome the attractive forces of the other particles in the liquid.

44
Q

Describe how temperature affects evaporation?

A

Higher temperature = more evaporation.
Because particles have a higher average kinetic energy – more particles have enough kinetic energy to break the forces of attraction and leave the liquid at the surface.

45
Q

Describe how surface area affects evaporation?

A

Larger surface area = More evaporation.
More particles near the surface, so more particles in the correct position and with enough energy to escape.

46
Q

Describe how air movement affects evaporation?

A

More air movement = more evaporation.
If air is moving over liquid surface – particles that escape, the surface of the liquid can’t drop back into the liquid – as the air will carry them away.

47
Q

Explain the cooling of an object in contact with an evaporating liquid?

A

As a liquid evaporates – average KE of remaining particles decreases.
As the liquid cools – energy transferred to the liquid from any object in contact with it.
As energy is transferred away from that object – the object cools down.

physics (10 decks)

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