Specific Latent Heat & Melting and Boiling

When ice melts to become water, which force must be overcome?

• the attraction between electrons and the nucleus

• the attraction between the atoms in a molecule

• the force between molecules

• the force of gravity

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

A substance is heated in an enclosed space until it becomes a gas.

After the heater is removed, the temperature is recorded at regular intervals. The graph shows

temperature plotted against time.

What does the section PQ represent?

• boiling

• condensing

• melting

• solidifying

Tags

NGSS.MS-PS1-4

The energy required to change liquid water into water vapour at the same temperature is called

latent heat of vaporisation.

What does this energy do?

• increases the average separation of the water molecules

• increases the average speed of the water molecules

• raises the temperature of the air near the water

• splits the water molecules into their separate atoms

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

A 2 kW kettle containing boiling water is placed on a balance. It is left there and continues to boil

for 5 minutes. The balance reading changes by 0.2 kg.

What does this information give as a value for the specific latent heat of vaporisation of water?

• 2000 J/kg

• 3000 J/kg

• 50 000 J/kg

• 3 000 000 J/kg

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Ice at –10 °C is heated at a constant rate until it is water at +10 °C.

Which graph shows how the temperature changes with time?

• 
• 
• 
• 

Tags

NGSS.MS-PS1-4

Some ice cubes are taken from a deep-freeze and placed in a metal container. The container is

heated at a constant rate and readings of temperature and time are taken. The results are

recorded on a graph.

Which temperature corresponds to 0 °C?

• A

• B

• C

• D

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

A hot liquid is carefully poured into a beaker. The graph shows how its temperature changes as it

cools towards room temperature.

Which processes are taking place at region X?

• boiling and evaporation

• condensation only

• evaporation only

• solidification and evaporation

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

An ice-cube has of mass of 7.50 g. The ice-cube is at 0°C.

Heat from the surroundings reaches the ice-cube at an average rate of 1.25 J/s.

How long does it take for all of the ice to melt?

(specific latent heat of fusion of ice = 333 J/g)

• 35.5 s

• 55.5 s

• 2000 s

• 3120 s

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Ice is taken from a freezer and left in a room. The ice melts and eventually the water reaches

room temperature.

Which energy transfers take place?

• A

• B

• C

• D

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

The graph shows the cooling curve of a hot substance.

In which part of the curve is latent heat released?

• PQ

• QR

• RS

• ST

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4