F3b Activity Core The effect of salt on the boiling point of water We have already seen that impurities such as salt can affect the freezing point of water. In this activity we will be looking to see if impurities such as salt can also affect the boiling point of water. Remember when salt dissolves in water it produces a salt solution. A salt solution is an example of a mixture. Equipment ● boiling tube ● Bunsen burner ● pure water (liquid A) ● thermometer ● heatproof mat ● salt solution (liquid B) ● clamps Planning and predicting Before you carry out this activity: 1 Write down what you predict will happen to the temperature of the pure water and the salty water as you heat each of them. Obtaining evidence 1 Put about 5 cm depth of liquid A (pure water) into the boiling tube and clamp the tube at an angle as shown. 2 Adjust the Bunsen burner to give a small flame. 3 Start heating the boiling tube. 4 Clamp the thermometer so that the bulb of the thermometer is in the liquid, as shown in the diagram. 5 When the liquid boils, record the highest temperature shown. 6 Repeat the experiment with liquid B. Considering the evidence 2 What was the boiling point of the pure water (liquid A)? 3 Was the boiling point of the salt solution (liquid B) the same, higher than or lower than that of the pure water? 4 How does this temperature value compare to your prediction in question 1? Evaluating 5 What appears to be the effect of salt on the boiling point of water? Sheet 1 of 1 © Harcourt Education Ltd 2004 Catalyst 2 This worksheet may have been altered from the original on the CD-ROM. Wear eye protection. heat 6 What would happen to the freezing point and boiling point of water if we substituted sugar for the salt? Extension

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Page 1: F-Activity.qxd 25-Nov-03 9:05 AM Page 11 F3b The effect of

F3bActivity

CoreThe effect of salt on the boilingpoint of water

We have already seen that impurities such as salt can affect thefreezing point of water. In this activity we will be looking to see ifimpurities such as salt can also affect the boiling point of water.Remember when salt dissolves in water it produces a salt solution.A salt solution is an example of a mixture.

Equipment● boiling tube ● Bunsen burner ● pure water (liquid A)● thermometer ● heatproof mat ● salt solution (liquid B)● clamps

Planning and predictingBefore you carry out this activity:

1 Write down what you predict will happen to the temperature of the pure water andthe salty water as you heat each of them.

Obtaining evidence1 Put about 5 cm depth of liquid A (pure water) into the

boiling tube and clamp the tube at an angle as shown.2 Adjust the Bunsen burner to give a small flame.3 Start heating the boiling tube.4 Clamp the thermometer so that the bulb of the thermometer

is in the liquid, as shown in the diagram.5 When the liquid boils, record the highest temperature shown.6 Repeat the experiment with liquid B.

Considering the evidence2 What was the boiling point of the pure water (liquid A)?3 Was the boiling point of the salt solution (liquid B) the same,

higher than or lower than that of the pure water?4 How does this temperature value compare to your prediction in question 1?

Evaluating5 What appears to be the effect of salt on the boiling point of water?

Sheet 1 of 1© Harcourt Education Ltd 2004 Catalyst 2This worksheet may have been altered from the original on the CD-ROM.

Wear eyeprotection.

heat

6 What would happen to the freezing point and boiling pointof water if we substituted sugar for the salt?

Extension

F-Activity.qxd 25-Nov-03 9:05 AM Page 11