A student investigated the addition of four different solids, A, B, C and D, to water. Five experiments were carried out. Experiment 1 By using a measuring cylinder, 30 cm3 of distilled water was poured into a polystyrene cup and the initial temperature of the water was measured. 4 g of solid A was added to the cup and the mixture stirred with a thermometer. The temperature of the solution was measured after 2 minutes.
Experiment 2 Experiment 1 was repeated using 4 g of solid B.
Experiment 3 Experiment 1 was repeated using 4 g of solid C.
Experiment 4 Experiment 1 was repeated using 4 g of solid D.
Experiment 5 A little of the solution from Experiment 4 was added to a little of the solution from Experiment 2 in a test-tube. The observations were recorded. observations: A fast reaction. Vigorous effervescence and bubbles produced.
Use the thermometer diagrams for Experiments 1-4 to record the initial and final temperatures in Table 4.1. Calculate and record the temperature difference in Table 4.1.
Table 4.1
experiment temperature / °C final temperature / °C difference / °C 1 2 3 4
Draw a labelled bar chart of the results to Experiments 1, 2, 3 and 4 on the grid below.
Use the results and observations from Experiments 1-5 to answer the following questions.
i)
Which solid dissolves in water to produce an exothermic reaction?
[1]
ii)
Give a reason why you chose this solid.
[1]
Which Experiment produced the largest temperature change?
Predict the temperature change that would happen if
i)
8 g of solid B were used in Experiment 2
[1]
ii)
60 cm3 of water was used in Experiment 4 [1]
iii)
Explain your answer to (e)(ii)
[2]
Suggest an explanation for the observations in Experiment 5.
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