P6 Molecules and Matter

Question 1

What is density?

Answer 1

Density describes how closely packed the particles are in a solid, liquis or gas.

Question 2

How do you find density?

Answer 2

Denisty = Mass / Volume

Question 3

What is the scientific unit of density?

Answer 3

Kg/m^3

Question 4

What is internal energy?

Answer 4

It is the total of kinetic energy and potential energy of all the particles in an object.

Question 5

What is potential energy?

Answer 5

Energy due to the indiviudal postions of a particle relative to another

Question 6

What is the density of water?

Answer 6

1000 kg/m^3

Question 7

What happens to the mass of a substance when it changes state?

Answer 7

It stays the same as number of particles don’t change

Question 8

What is required to melt a solid and boil a liquid?

Answer 8

Energy

Question 9

What is the difference between boiling and evaporating?

Answer 9

During evaporation particles only leave from the surface of the liquid whereas in boiling bubbles of gas are formed throughout the liquid.

Question 10

What do the flat sections of a temperature-time graph show?

Answer 10

Melting and boiling point

Question 11

Why does temperature remain constant at the boiling/melting point when the internal energy is increasing?

Answer 11

There is a change of state occuring here so potential energy increases but kinetic energy remains constant

Question 12

What is the specfic latent heat of a substance?

Answer 12

The amount of energy required to melt or boil 1Kg of a substance

Question 13

What is specific latent heat of fusion?

Answer 13

The amount of energy required to change the state of 1Kg of a substance from a solid to a liquid

-in joules

Question 14

What is specific latent heat of vapourisation?

Answer 14

The amount of energy required to change the state of 1Kg of a substance from a liquid to a vapour.

-in joules

Question 15

How do you calculate the specific latent heat of a substance?

Answer 15

Specifc latent heat = energy (j) / mass (kg)

Question 16

What determines the state of a substance?

Answer 16

The strength of the forces of attraction.

Question 17

When a substance is heated ….

Answer 17

• if the temperature rises, the kinetic energy of the particles increase
• if it melts or boils, the potential energy of the particles increase

Question 18

What causes the pressure of gas on a surface?

Answer 18

Particles of gas repeatedly hitting the surface.

Question 19

How can the specifc latent heat of ice (or water) be measured?

Answer 19

By using a low-volatge heater to melt the ice (or boil the water)

Question 20

Why does the pressure of gas increase if the temperature is increasing in a sealed container?

Answer 20

the molecules move faster so they hit the surfaces with more force

Question 21

What can be used as evidence of the random motion of gas molecules?

Answer 21

The unpredictable motion of smoke.

Question 22

How do you find the density of an irregular object?

Answer 22

1) Measure the mass on a balance
2) Fill a Eureka can with water up to it’s spout
3) Slowly place the object into the water
4) Collect and measure the volume of water displaced using a measuring cylinder
5) The volume displaced is equal to the volume of the rock

density = mass / volume

Question 23

How do you find the density of a regular object?

Answer 23

1) Measure it’s mass on a balance
2) Measure it’s volume using a vernier calliper
3) Denisty = mass / volume

Question 24

How do you measure the denisty of a liquid?

Answer 24

1) Place a beaker onto a balance and zero the balance
2) Pour 10ml (10cm^3) into the beaker
3) Measure the mass of it
Density = mass / volume

(note : larger the volume the more accurate density is)