Cooling Drinks

1) What is the specific latent heat of fusion of water?

Specific latent heat of fusion is the amount of heat absorbed or released by a substance when changing states. This could be boiling or melting. Latent heat of fusion is the amount of energy needed to melt a substance, while latent heat of vaporisation is the amount of energy needed to boil a substance. The specific latent heat of fusion of water is 334 j/g In the graph, you can see that as the temperature increases more energy is needed to heat the water. When the temperature hits the latent heat of fusion, the temperature stops rising as the energy is being used to change the state of water. This also happens when the latent heat of vaporisation

2) What is the specific heat capacity of water?

The specific heat capacity is the amount of heat that is needed to raise the temperature of a substance. The specific heat capacity water is 4181 j/kg. This is higher than most metals. Here are some other substances with their specific heat capacity; Substance

C (J/g oC)
Air
1.01
Aluminium
0.902
Copper
0.385
Gold
0.129
Iron
0.450
Mercury
0.140
Sodium Chloride
0.864
Ice
2.03
Water
4.18

3) Why energy is needed to melt ice and how this is explained by the structures of ice and water The molecules of H20 behave differently in water than in ice. In water they are floating around freely and in ice they are “stationary”, they only vibrate slowly. This is because they don’t have enough energy to break their intermolecular bonds. So in order to melt ice you need to add energy to give the molecules kinetic energy to move around, becoming less stationary. If enough energy is given to the molecules they break the intermolecular bonds and the ice melts to ice. 4) Why is ice more effective for cooling a drink than cold water The cooling of a drink with a cube of ice is more effective than using cold water because ice can absorbs a lot more heat. This is because it has a higher specific latent heat of fusion.

HypothesisThe greater the amount of ice that melts the bigger the temperature drop of the water This is because when more ice melts more energy is taken from the water

Apparatus

5 identical beakers which are made of the same materials
Thermometers with a suitable range; -10oC to 100oC
Measuring with volume above 200cm3
Top-pan balance reading with up to 35g
Ice (crushed), not straight form the freezer
Suitable insulating material
Means of removing water e.g. paper towels
Stopwatch to measure time in minutes and seconds

Method

1) Pour 200cm3 of water into 4 same sized beakers of the same materials. This is so the materials does not affect the in temperature 2) I’m going to measure the temperature of the water. I’m going to make sure the temperature is the same to make it a fair test. I’m going to leave the water to become room temperature for about 5 minutes 3) I’m going to add 15g of ice to Beaker 1, 25g to Beaker 2, 25g to Beaker 3 and the fourth Beaker will have no ice.

The fourth beaker will set the benchmarks. The amount of ice is the independent variable. I will measure the ices mass by using the top-pan balance. I used these certain amount of mass so I have a big range of data and will make a better comparison. 4) I will then measure the temperature of the beakers every minute for three minutes. 5) Then I will put all my results into a table and then into a line graph so I can make easy comparisons Hazards, the risks and how to reduce the risks

Results Table

1. Describe any patterns or trends in your results. Comment on any unexpected results. After analysing my result I have found some trends in the data. I also saw some anomalies that came up in the experiment. The most obvious trend is in the line graph and the temperature drop. The more mass of ice I put into the beaker to cool the drink, the faster the temperature dropped. For example, in beaker one 2. Compare results of your own investigation (Part 2) with the data from other groups within your class and any data collected in Part 1. Comment on any similarities and differences.

Suggest and explain possible reasons for any differences. 3. Evaluate your results, the method you used and how well you managed the risks. 4. Do your results from Part 2 support the hypothesis suggested by Charlie’s friend? Explain your answer. 5. It is possible to use the equations below to predict the temperature drop of the water when a chosen amount of ice is added to it. Will the actual temperature drop, measured in your experiment, be equal to the predicted value? Use relevant scientific explanations in your answer. Use the results of your experiment, appropriate calculations and your research (Part 1) to provide evidence to support your answer. 1 cm3 of water has a mass of 1 g

Energy = mass × specific heat capacity × temperature change Energy = mass × specific latent heat