Melting, boiling and evaporation

Within a liquid, a number of high-energy molecules escape from the surface even though the liquid is not hot enough for bubbles to be produced. What is the name of this process?

May/June 2015

A pupil places $37\,\text{g}$ of ice at $0\,^{\circ}\text{C}$ into $100\,\text{g}$ of water at $30\,^{\circ}\text{C}$. After mixing, the water and the melted ice both have a final temperature of $0\,^{\circ}\text{C}$. There is no transfer of heat to the surroundings or from them. The specific heat capacity of water is $4.2\,\text{J g}^{-1}\,^{\circ}\text{C}^{-1}$. Determine the specific latent heat of ice.

May/June 2015

A student draws a diagram showing the molecules in a liquid, as in Fig. 10.1.

May/June 2015

State what melting point means.

May/June 2016

A beaker containing water is set on a hot-plate until it boils, as illustrated in Fig. 4.1. The hot-plate sits on a balance that records the mass of water in the beaker. The liquid remains boiling for a long period. Bubbles are seen in the boiling water.

May/June 2016

Four beakers each have the same volume of water, but the water is at two different temperatures. The beakers are left in the open air. In which beaker does the water evaporate most quickly?

May/June 2017

The table gives the melting points and boiling points of several elements. Which element remains liquid across the widest temperature range?

May/June 2017

Several ice cubes are removed from a freezer and warmed in a container. Temperature and time readings are plotted on the graph. Which temperature is $0^\circ\text{C}$?

May/June 2017

A few ice cubes are removed from a freezer and warmed in a container. Temperature and time readings are plotted on the graph. At what temperature is $0\,^\circ\text{C}$?

May/June 2017

An ice-cube tray contains $30\,\text{g}$ of water. The specific latent heat of fusion of ice is $3.3 \times 10^5\,\text{J kg}^{-1}$. Calculate the thermal energy that must be removed from the water at $0\,^\circ\text{C}$ so that it becomes ice at $0\,^\circ\text{C}$.

May/June 2017

What is meant by ‘the escape of the more energetic molecules from a liquid surface’?

May/June 2018

Describe two ways in which boiling and evaporation differ.

May/June 2018

Latent heat is the thermal energy required to change a solid into a liquid.

May/June 2018

How can latent heat be defined?

May/June 2019

Steam at $110^\circ\text{C}$ condenses on a surface, forming water droplets at $100^\circ\text{C}$. What occurs after the steam makes contact with the surface?

May/June 2022

Which row gives the description of boiling and evaporation of a liquid?

May/June 2022

A hairdryer is blown over the surface of water in a beaker so that the water evaporates. What would make the rate of evaporation of the water increase?

May/June 2022

Define the term latent heat of fusion.

May/June 2022

A partially completed statement about latent heat is shown below. Latent heat is the ............ needed to overcome the bonds between molecules and change the ............ of a substance. Which words should be placed in gap 1 and gap 2 to complete the sentence correctly?

May/June 2023

Boiling and evaporation are different processes. Which of the statements below is correct?

May/June 2024

A bottle filled with a cold liquid is left on a table on a warm day. Water droplets appear on the outside of the bottle. Which process makes the droplets appear?

May/June 2024

As a liquid evaporates, molecules leave from the surface. Which molecules are able to leave, and what happens to the mean kinetic energy of the molecules that stay in the liquid?

May/June 2025

A beaker contains a sample of water at temperature $T$. The water has a surface area of $A$, and an electric fan drives air over the top of the beaker with speed $v$. For which values of $T$, $A$ and $v$ does the water evaporate at the greatest rate?

May/June 2025

What does the term latent heat of vaporisation mean?

Oct/Nov 2015

In the diagrams, part of the liquid in a dish evaporates. Which molecules leave the liquid, and which molecules in the liquid have the higher average kinetic energy?

Oct/Nov 2015

In a steam cleaner, water is raised to its boiling point and then changed into steam (water in the gas state).

Oct/Nov 2015

As a liquid evaporates, molecules leave from the surface. Which molecules are the ones that leave, and what happens to the average kinetic energy of the molecules left in the liquid?

Oct/Nov 2016

The diagram illustrates changes of state. What are the names of the changes of state $P$, $Q$, $R$ and $S$?

Oct/Nov 2016

A boiling liquid takes in thermal energy (heat) at a rate of $450\,\text{W}$. The specific latent heat of vaporisation is $2.7 \times 10^6\,\text{J kg}^{-1}$. What mass of liquid is vaporised in $9.0\,\text{minutes}$?

Oct/Nov 2016

An image of a sheet ripped from an exercise book is shown. “…and some particles at the surface acquire enough kinetic energy to escape, carrying that energy away with them.” Which process is this describing?

Oct/Nov 2016

A liquid sample at $100\,^\circ\text{C}$ is left to cool until it reaches a room temperature of $20\,^\circ\text{C}$. The graph shows the way the temperature varies with time as the sample cools. At what time is the sample fully solidified?

Oct/Nov 2016

An electric heater produces thermal energy for three minutes, and this is used to melt wax. At the start, the wax is already at its melting point of $60\degree\text{C}$. The specific latent heat of the wax is $220\ \text{J g}^{-1}$. The heater transfers $7700\ \text{J}$ of thermal energy to the wax. How much wax melts?

Oct/Nov 2016

Fig. 4.1 depicts a kettle of water on the burner of a gas cooker. The gas burner is ignited at time $t = 0$. By $t = 250\,\text{s}$, the water reaches $100^{\circ}\text{C}$, which is the boiling point of water.

Oct/Nov 2016

A student studies how surface area changes the rate at which water evaporates at room temperature.

Oct/Nov 2016

Scientists think that some lakes are becoming smaller because of evaporation. What makes the rate of evaporation increase?

Oct/Nov 2017

A sample of solid wax is heated until it melts in a boiling tube and then left to cool down. The graph shows the cooling curve. What is happening between points X and Y?

Oct/Nov 2017

When a substance boils or melts, it either absorbs energy or releases energy. Which row shows the energy transfer for the change of state?

Oct/Nov 2017

A container of liquid is left on a laboratory bench. Part of the liquid evaporates. What occurs, and what is the reason for it?

Oct/Nov 2017

Solid wax is heated until it melts in a boiling tube and is then left to cool down. The graph shows the cooling curve. What is taking place between points $X$ and $Y$?

Oct/Nov 2017

Old gold jewellery is heated in a furnace until it melts. Fig. 3.1 shows the molten gold being poured into a mould so that a gold bar is formed. The melting point of gold is $1100\,^{\circ}\text{C}$.

Oct/Nov 2017

What gets larger when a liquid changes into a gas at its boiling point?

Oct/Nov 2018

On a warm day, a cold bottle of drink is set on a table. Water droplets appear on the outside of the bottle. Which process leads to the droplets forming?

Oct/Nov 2018

A 100 g sample of lead, initially solid at room temperature, is heated. By 22 s, it has completely melted. The graph plots how the temperature changes with time. The heater has a power of 320 W. Which expression gives the specific latent heat, in J kg$^{-1}$, for the lead?

Oct/Nov 2018

What rises when a liquid changes into a gas at its boiling point?

Oct/Nov 2018

What is the term for the change of state when a substance goes from a solid to a liquid?

Oct/Nov 2019

A glass beaker is standing in a warm room and contains water. At the start, the water is at the same temperature as the room. Which alteration would not change the initial rate at which the water evaporates?

Oct/Nov 2019

A student gives four statements about evaporation and boiling. Which two statements are correct?

Oct/Nov 2019

What is the definition of specific latent heat?

Oct/Nov 2019

A beaker of water is set on an electric hotplate and heated until it boils. While boiling, the water changes from a liquid to a gas.

Oct/Nov 2019

In many countries, solid salt is made by holding sea-water in large, shallow ponds and leaving the water to evaporate away. Fig. 4.1 illustrates salt being produced in this manner.

Oct/Nov 2019

Fig. 9.1 shows a liquid boiling at its boiling point, enclosed in a cylinder by a piston. An electric heater is placed in the liquid and linked to a power supply. The thermal energy from the heater slowly changes the boiling liquid into a gas.

Oct/Nov 2019

A student has a thermometer with no temperature markings, as shown in Fig. 4.1.

Oct/Nov 2019

Which statement correctly describes the melting of ice and the boiling of water?

Oct/Nov 2020

A small glass measuring cylinder containing oil is put in a freezer held at $-18^\circ\text{C}$. Fig. 9.1 plots the way the oil’s temperature changes with time $t$.

Oct/Nov 2020

A student performs an experiment to determine a value for the specific latent heat of fusion of ice. He has to find the mass of ice melted by the heater in time $t$. He uses the apparatus shown in Fig. 2.1.

Oct/Nov 2020

The graph shows temperature against time for a wax sample being heated until it melts. The wax has a mass of $200\,\text{g}$. Thermal energy is delivered to the wax at a steady rate of $12000\,\text{J min}^{-1}$. What is the specific latent heat of fusion of the wax?

Oct/Nov 2021

The diagram shows a liquid at room temperature in a beaker. Which change reduces the rate at which the liquid is lost by evaporation?

Oct/Nov 2021

The graph shown is a temperature-time graph for a wax sample that is being heated until it melts. The wax has a mass of $200\,\text{g}$. Thermal energy is delivered to the wax at a steady rate of $12\,000\,\text{J minute}^{-1}$. What is the specific latent heat of fusion of the wax?

Oct/Nov 2021

The water in four beakers is at different temperatures, and the surface area of the water in each beaker is also different. In which beaker is the water evaporating at the fastest rate?

Oct/Nov 2021

A 1 kg sample of a substance keeps a definite shape. When thermal energy is added to it, the attractive forces between its molecules become weaker. What is taking place?

Oct/Nov 2022

Under which conditions does a liquid evaporate at the fastest rate?

Oct/Nov 2022

A temperature-time graph is shown for a material that is being heated while it is still solid. Which row correctly shows what is taking place at X, Y and Z?

Oct/Nov 2023

Fig. 5.1 shows a device that lowers the temperature of room air by evaporation. Water runs from the container into the sponge block, so it stays damp. Air enters through one grille and leaves through the other. When the air passes through the damp sponge block, the water in the sponge block evaporates.

Oct/Nov 2023

The melting temperature of a substance is $-17\,^{\circ}\text{C}$ and its boiling temperature is $117\,^{\circ}\text{C}$. At $-10\,^{\circ}\text{C}$ and at $110\,^{\circ}\text{C}$, in what state is the substance?

Oct/Nov 2024

A fixed mass of a substance, initially in the solid state, receives thermal energy at a steady rate. The graph illustrates how the temperature of that fixed mass changes with time. At which parts of the graph does the substance take in latent heat?

Oct/Nov 2024

The diagram represents a liquid in a beaker at room temperature. What decreases the rate at which liquid is lost by evaporation?

Oct/Nov 2024

A student uses ice cubes to investigate how long ice cubes of different masses take to melt when they are placed in water.

Oct/Nov 2024

A large test-tube holds a thermometer and some solid wax at 21^{\circ}C. At time t = 0, the test-tube is partly dipped into a beaker of boiling water, and the wax temperature is measured for the next 600 s. Fig. 4.1 shows how the temperature of the wax changes with time t.

Oct/Nov 2025