P6 Molecules and matter Flashcards

1
Q

Boiling point

A

Temperature at which a pure substance boils or condenses

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2
Q

Density

A

Mass(kg) per unit volume of a substance(m3)

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3
Q

Freezing point

A

The temperature at which a pure substance freezes. Freezing point = melting point of the solid

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4
Q

Internal energy

A

The energy of the particles of a substance due to their individual motion and positions

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5
Q

Latent heat

A

The energy transferred to or from a substance when it changes its state

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6
Q

Melting point

A

Temperature at which a pure substance melts or freezes

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7
Q

Physical change

A

A change in which no new substances are produced

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8
Q

Pressure

A

Force per unit cross-sectional area for a force acting on a surface at right angles to the surface

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9
Q

Specific latent heat of fusion

A

Energy needed to melt 1kg of a substance with no change of
temperature, energy needed to change the state of 1kg of the substance from solid to liquid at its melting point and for the particles to break free from each other.

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10
Q

Specific latent heat of vaporisation

A

Energy needed to boil/condense 1kg of a substance with no change of
temperature.

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11
Q

How does temperature of the surroundings affect the average speed of the particles as well as the kinetic and thermal energy of the particles(on average)?

A

On average, as the temperature of the surroundings of the particles increases, the average speed of/kinetic/thermal energy of the particles increases as the particles move around more.

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12
Q

What is the property of solid(in that state)

A

It keeps the same shape(can’t flow).
It also has a fixed volume.

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13
Q

What is the property of liquid(in that state)

A

Keeps the same volume and can’t be compressed
Flows and takes the shape of its container

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14
Q

What is the property of gas(in that state)

A

Flows and expands to fill its container
Its volume
Can be compressed and expands to fill a container

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15
Q

Property of solid particles

A

Particles vibrate around a fixed position
Particles are held close together in a
fixed arrangement

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16
Q

Property of liquid particles

A

Particles can move around but stay close together, moving about at random
Particles close together but not in fixed positions

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17
Q

Property of gas particles

A

Particles move around very fast
Particles move far apart and randomly- this is why the density of a gas is much less than that of a solid or a liquid. There are almost no forces of attraction between the particles

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18
Q

Why can’t you compress a solid or a liquid!

A

In a solid, particles are touching which makes it as dense as possible so you can’t compress it and in a liquid particles are close so you can’t compress it easily.

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19
Q

Does pressure go higher or lower going down the ocean?

A

Pressure increases going down the ocean

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20
Q

Does atmospheric pressure increase or decrease going higher up!

A

The atmospheric pressure decreases going higher up as there are less particles on top pushing you down.

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21
Q

Pressure

A

Force/Area

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22
Q

How does heating up the gas particles affect the pressure of a material?

A

If we heat up the gas particles, particles are hotter and move faster, meaning they have more momentum and there is higher force of the particles on the sides of the container, so pressure increases and the material expands. Molecules of gas collide repeatedly with each other and with the surface inside their container, rebounding after collision, the total force causes a steady pressure on the surface inside the container.

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23
Q

How to decrease pressure applied

A

Either weigh less or use skis, snowboards or snow shoes(with a larger area)

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24
Q

Differences between property of objects in a state of matter and particles of objects in a state of matter

A

Particles in an object have different properties to the actual state of matter in an object e.g, gas particles aren’t compressibe or able to change volume, but a gas can

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25
Q

Condensation

A

Change of state of an object from gas to liquid(cooling)

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26
Q

Sublimation

A

Change of state of an object from solid to gas

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27
Q

Mass

A

How much stuff there is in the material(kg)

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28
Q

Volume

A

How much space the material takes up(m3)

29
Q

Density(required practical- for an irregular shaped object)

A

1)Find the mass of the object(using a top pan balance)
2)Fill the eureka can with water just below the spout and allow the excess to drain out into the beaker and throw the excess water away. Place a measuring cylinder beneath the spout
3)Place your object into the eureka can and collect displaced water into the measuring cylinder.
4)Use a measuring cylinder to find the volume of the displaced water.
5)Repeat for many different objects

30
Q

1PA=

A

1N/m2

31
Q

Archimedes’ Principle

A

The volume of a displaced fluid is equal to the volume of an object fully immersed in the fluid

32
Q

Fluidity

A

Molecules moving past each other and taking the shape of a container

33
Q

Compressibility

A

Measure of how the volume of a body changes when pressure is applied

34
Q

Pure substance

A

A substance with only one type of atom or molecule

35
Q

Melting point

A

Temperature a substance changes state(melting/freezing)

36
Q

How do impurities in a substance(different melting and boiling points) affect the melting and boiling points of a mixture of substances?

A

Impurities in a substance change the melting and boiling points in
a mixture of substances
e.g. salt lowers the melting point of water

37
Q

Experiment-Changes in state(equipment)

A

Ice
Boiling tube
Tripod
Gauze
Stopwatch
Beaker
Bunsen burner
Safety mat
Thermometer
1)Set up equipment as instructed
2)Place the ice into the boiling tube and place this in a beaker of water, taking the first reading of temperature at time 0 seconds.
3)Heat the water taking temperature reading every 30 seconds.
4) Measure the temperature of the substance when it melts.
5) Use the same arrangement without the beaker of water to find the boiling point of a liquid.
Safety: Don’t let the Bunsen burner evaporate all the water from the beaker.
Wear eye protection.

38
Q

Heating curve

A

If a solid’s heated at melting point, the temperature rises until it reaches the melting point of the solid, where the temperature stops rising until the solid melts as physical bonds are broken. This is because heat energy goes into separating the particles rather than raising the temperature. Once the solid melts, the temperature rises again until it reaches the boiling point. Here, the temperature again stays the same as energy goes into further separating the particles and breaking the bonds between particles.

39
Q

Thermal energy supplied to/lost by body=

A

Mass of the body x specific latent heat(J kg -1)

40
Q

Specific heat capacity

A

Thermal energy required to raise the temperature of a body of mass 1kg by 1C without a change in state

41
Q

Thermal energy =

A

Mass x specific heat capacity(J/kg C)x temperature change

42
Q

What does internal energy consist of?

A

It’s the combined energy of the kinetic(due to motion of individual particles) and potential(due to position of individual particles relative to each other), energy of the particles in the substance. It’s the energy stored by the particles of a substance.

43
Q

What factors change internal energy

A

Heating the substance increases the overall internal energy as it increases the particles’ kinetic energy. This means the temperature of the substance increasing increases the kinetic energy of the particles.
A change in state(melting/boiling) changes the potential energy of the particles, so the overall internal energy. When the physical state of a substance changes, the total potential energy of its particles change.

44
Q

Forces in a solid

A

There are strong forces of attraction between the particles causing them to remain in fixed positions. Each particle vibrates in fixed positions and given more energy(after being heated) particles vibrate and with enough energy break away from forces holding the structure, turning into a liquid. The solid being heated means it either melts or sublimates.

45
Q

Forces in a liquid(how vaporisation can occur)

A

There are weaker forces of attraction between particles in a liquid than in a solid,
these weaker forces can’t hold the substance in a rigid structure but stop them leaving the substances’ surface. With enough energy(after being heated), particles break away from these forces as they gain enough energy and change to the gas state, breaking from the liquid surface.

46
Q

Forces in a gas

A

The forces holding particles are weak, allowing the particles to move at high speeds in random directions. With more energy(after being heated), gas particles gain kinetic energy and move faster, so collide with each other and surfaces more frequently and with more force, which creates gas pressure.

47
Q

Brownian motion of particles in a liquid or air

A

The random motion of particles(diffusion) suspended in a fluid was due to collisions with molecules in the fluid(internal energy in fluid causes these molecules to move randomly)

48
Q

Difference between evaporation and boiling

A

Evaporation occurs at any temperature, but boiling only occurs at one temperature(the boiling point).

49
Q

Deposition

A

Change of state from a gas to a solid

50
Q

Density

A

Mass/volume, density is represented in kg/m3

51
Q

1000kg/m3=

A

1g/cm3

52
Q

How to measure the density of a solid

A

To measure the mass of the object, use an electronic balance.
The volume of a regular solid should be worked out by measuring its dimensions using a milimetre ruler, vernier callipers or micrometer and multiply them together.
For a small, irregular solid, lower it on a thread into a measuring .
cylinder partlu filled with water and work out the volume of the object by the rise in the water.
Then use the equation density = mass/volume to calculate the density of the object.
Safety: Don’t spill any liquids

53
Q

How to measure the density of a liquid

A

Use a measuring cylinder to measure the volume of a certain amount of liquid. Measure the mass of an empty beaker using a balance. Remove the beaker from the balance and pour the liquid from the measuring cylinder into the beaker. Use the balance again to measure the total mass of the beaker and the liquid. Calculate the mass of the liquid by subtracting the mass of the empty beaker from the total mass of the beaker and the liquid.
Use the equation density = mass/volume
Safety: Don’t spill any liquids

54
Q

1m3

A

1000000cm3

55
Q

Which objects float in water?

A

Objects that have a lower density than water(1000kg/m3).

56
Q

Examples of physical changes

A

When water in a kettle boils, the water turns into steam/water vapour.
When solid carbon dioxide warms up, the solid turns into gas directly.
When steam touches a cold surface, the steam condenses and turns into water.

57
Q

Conservation of mass

A

The mass of a substance is conserved even when a substance changes state, because the number of particles in a substance stays the same.

58
Q

Different amounts of energy between particles of a substance in its solid, liquid and gas states

A

For a given amount of a substance:
The particles have more energy in the gas state than they have in the liquid state.
The particles have more energy in the liquid state than in the solid state.

59
Q

What is the temperature of water when it’s heated and boils at atmospheric pressure?

A

100C(the boiling point).

60
Q

What is the temperature of pure ice when it’s heated and melted?

A

Its temperature stays at 0C until all the ice has melted.

61
Q

When does evaporation from a liquid occurs?

A

Evaporation from a liquid happens at any temperature, boiling occurs only at the substance’s boiling point.

62
Q

What does the flat section of a temperature-time graph show?

A

The melting/boiling point of the substance

63
Q

Specific latent heat of fusion

A

If energy is transferred to a solid at its melting point, and mass of the substance melts without change in temperature:
Specific latent heat of fusion(J/kg)= Energy(Joules)/Mass(kg)

64
Q

Change in thermal energy=

A

Mass x specific heat capacity(J/kg C) x temperature change

65
Q

Specific latent heat of vaporisation(equation)

A

If energy is transferred to a liquid at its boiling point, and mass of the substance boils away without change in temperature:
Specific latent heat of vaporisation(J/kg)= Energy(joules)/Mass(kg)

66
Q

Why should we never heat food in a sealed can?

A

Becquse the can will explode as the pressure of gas inside increases as the temperature increases. This is because:
The energy transferred to the gas when it’s heated increases the kinetic energy of its molecules, so the average kinetic energy of the gas molecules increases when the temperature of the gas is increased.
The average speed of the molecules increases when the kinetic energy increases, the molecules on average hit the container surfaces with more force and more often, so the pressure of the gas increases. Molecules move faster and the number of impacts per second of gas molecules on the surfaces of a sealed container increases, so the total force of impacts increases.

67
Q

Observing random motion.

A

1) A small glass cell is filled with smoke.
2) Light is shone through the cell.
3) The smoke is viewed through a microscope.
4)You see the smoke particles constantly moving and changing direction.

68
Q

How would a decrease in temperature in the balloon change the balloon

A

The gas particles won’t have the kinetic energy or momentum to rapidly collide with each other and the surface of their container, the inside wall is hit with less force.
This results in decreasing pressure inside the balloon, but pressure outside the balloon remains constant to decrease the volume inside the balloon.