P6- Moelcules And Matter

Question 1

Give the equation for Density.

Answer 1

1) Density= Mass/Volume

Question 2

Explain how you would measure the density of a regular solid.
Exlplain how you would work out the Density of an irregular solid.

Answer 2

1) Use a ruler to measure its dimensions to work out the volume (lxwxh). Then to measure the mass of the object, use an electronic balance.
2) To work out the volume of an irregular solid, lower it on a thread into a measurng cylinder partially filled with water. The rise in water level will give you the voulume. To measure the mass, use the electronic balance.

Question 3

Explain how you would measure the Density of a liquid?

Answer 3

1) To measure the volume of the liquid, use a measuring cylinder. To work out the mass, using a balance, measure the mass of the beaker and then the mass of the beaker and the liquid. Simply subtract the mass of the liquid of the beaker and liquid from the mass of the beaker to have the mass.

Question 4

Explain the differences between solids, liquids and gases in terms of arrangement and movement of particles.

Answer 4

1) In a solid, particles are arranged in a fixed position and vibrate in this position, which means that they do not move. They have the least energy.
2) In a liquid, the particles are not fixed, they move about at random and are in contact with eachother. They have more energy than solids.
3) In gases, the partcles are not arranged, they can move freely, lots of spae between them, so collisions are more frequent. They have the most energy.

Question 5

Explain what happens to the mass of a substance when it changes state.

Answer 5

1) When an object changes state, its mass stays the same because the number of particles do not change.

Question 6

Explain what a substances boiling and melting point is.

Answer 6

1) A subsnaces boiling point is the temperature at which it boils/condenses.
2) A substances meltting point is the temperature at which it melts/solidifies.

Question 7

Explain the features of particles in a solid.

Answer 7

1) In a solid:
- Three dimensional structure. Strong forces of attraction. When heated, the particles energy store increases and vibrate more. It melts because the particles have gained enough energy to break away from eacother

Question 8

Explain the features of particles in liquids.

Answer 8

1) In liquids:
- Forces of attraction are not strong enough to hold particlles together in a rigid position. They are strong enough though to stop the particles moving away from eachother at the surface. When heated, some of the particles gain enough energy to break away from other particles.

Question 9

Explain the features of particles in gases.

Answer 9

1) In gases:
- Forces of attraction are so weak, they are insignificant. Particles move around at high speeds in random movments and collide with eachother and the internal surface of their container. The pressure of the gas on the solid is caused by the force impacts. When heated, the particles gain more energy which increases the frequency of collisions between the particles. Causes pressure to increase as well.

Question 10

Explain what happens to the energy stores of particles when it is heated.

Answer 10

1) When a substance is heated and the temp rises, the kinetic energy of its particles increase.
2) If it melts/boils, tehr potential energy of its particles increases.

Question 11

Explain what is meant by latent heat.

Answer 11

1) Latent heat is the energy needed for a substance to change its state without changing its temperature.

Question 12

Explain what Specific Latent heat of fusion/vaporisation is.

Provide the equation for Specific Latent Heat.

Answer 12

1) Specific Latent Heat of fusion/vaporisation is the energy needed to melt/boil 1kg of a substance without changing its tempertaure.
2) E= ml

Question 13

How can the specfic latent heat of ice/water be measured?

Answer 13

1) The secific latent heat of ice/water can be measured using a low-voltage heater to melt the ice/boil the water.

Question 14

Explain what the pressure of gases is caused by.

Answer 14

1) The pressure of gases is caused by the random impacts of gas molecules on surfaces that are in contact with the gas.

Question 15

Explain why the pressure of gases increase if the temperature inside a sealed container increases.

Answer 15

1) Molecules move faster so they can hit the surfaces with more force.
2) The number of impacts of gas molecules on the surfaces of the sealed container increases, which increases the frequency of collisions.

Question 16

How can you prove the random motion of gas molecules?

Answer 16

1) The upredictable motion of smoke particles can show this.
2) The air molecules repeatedly collide at random with each smoke particle.

Question 17

What is the equation for Boyle’s law?

Answer 17

1) pV= constant

Question 18

Explain the variation of pressure with volume.

Answer 18

1) The pressure is increased if volume is reduced because the space the molecules move in is smaller. The molecules hit the surface more often so the number of impacts increases.

Question 19

Explain how the temperature of a gas can increases rapidly if it compressed rapidly.

Answer 19

1) Work is done on it and the energy isnt transferred quickly enough to the surroundings.