In which changes do the particles move further apart?
Which change of state takes place during evaporation?
A sugar cube is dropped into a hot cup of tea.
The tea is not stirred.
Which statement explains why the tea becomes sweet?
Which statement is an example of diffusion?
A few drops of perfume were spilt on the floor. A few minutes later the perfume could be smelt a few metres away.
Which two processes had taken place?
‘Particles moving very slowly from an area of high concentration to an area of low
Which process is being described above?
In which substance are the particles close together and slowly moving past each other?
The diagram shows how the molecules in the exhaust gases diffuse into the air.
Which statement describes what happens to these molecules next?
A gas jar of bromine vapour and a gas jar of air are set up as shown in diagram 1.
The glass slide is removed. Diagram 2 shows the appearance of the gas jars after one hour.
Which statement explains why the bromine and air mix together?
A liquid is heated until it boils.
Which result shows that the liquid in the test-tube is pure water?
Small crystals of purple KMnO4 (Mr = 158) and orange K2Cr2O7 (Mr = 294) were placed at the
centres of separate petri dishes filled with agar jelly. They were left to stand under the same
After some time, the colour of each substance had spread out as shown.
The lengths of the arrows indicate the relative distances travelled by particles of each substance.
Which statement is correct?
Pure water has a boiling point of 100 °C and a freezing point of 0 °C.
What is the boiling point and freezing point of a sample of aqueous sodium chloride?
Which process causes the greatest increase in the distance between particles?
Which statement describes sublimation?
The apparatus shown is set up. After 20 minutes a white ring of ammonium chloride is seen at
Which statement about the molecules of ammonia and hydrogen chloride is correct?