Specific Heat Capacity Practical

Measuring the specific heat capacity of a metal Heat up the aluminium block (then water) enough to collect sufficient data to calculate its SHC. Take steps to reduce uncertainty as much as reasonable. Keep recording the temperature for another 5 minutes after switching the heater off. Amalgamate your results then compare your results with the known values for Al and water. Eg. Thermal insulation around the block would prevent it from cooling down after the heater is switched off. It may help to add a drop of water in the hole where the thermometer goes to make better thermal contact. Safety Switch the heater off if it is not in the block. The heater and metal blocks will become very hot.

Questions Estimate the uncertainty in the measurements of the current, the pd and the temperature rise. Assuming no heat transfer to the surroundings from the block takes place, the specific heat capacity of the metal =   For each block calculate: the electrical energy supplied to the block ( = current  pd  heating time) the specific heat capacity of the metal. Use your temperature measurements after the current was switched off to discuss the effectiveness of the insulation of each block. Discuss whether it is reasonable to assume that no heat transfer to the surroundings from the block takes place. Calculate the percentage uncertainty in the current and the pd and hence determine the percentage uncertainty in the energy supplied. Discuss whether the percentage uncertainty in the temperature rise is significant compared with the percentage uncertainty in the energy supplied.

Investigating the specific latent heat of fusion for ice a large plastic funnel two beakers a suitable low-voltage heater a mercury thermometer a low-voltage power supply an ammeter a voltmeter a stopwatch a top-pan balance a switch and variable resistor a supply of ice cubes paper towels a clamp and stand Method 2 Each group of students will need: an insulated calorimeter a beaker of warm water a beaker of ice cubes a tray

In the first method, a low-voltage heater is used to melt ice in a plastic funnel. A beaker is used to collect water from the funnel as the ice melts in the funnel. The mass of water collected in a certain time is measured without the heater on, and with the heater on, to enable the mass of water melted due to the heater to be calculated. In the second method, the paper towels are to be used to dry each ice cube when it is transferred to the water in the calorimeter. This is necessary for accuracy as the theory assumes only ice, not water, is transferred. Safety Students should be reminded to keep the ice and water away from the low-voltage power supply unit. Students should be warned not to touch the low-voltage power supply unit with wet or damp hands. Students should be reminded to dry their hands if they become wet or to clear up any water or ice that spills out of the beaker or funnel. In Method 2, the calorimeter and the beaker of ice should be placed in a tray on the bench to stop any ice cubes dropping onto the floor.

Safety Students should be reminded to keep the ice and water away from the low-voltage power supply unit. Students should be warned not to touch the low-voltage power supply unit with wet or damp hands. Students should be reminded to dry their hands if they become wet or to clear up any water or ice that spills out of the beaker or funnel. In Method 2, the calorimeter and the beaker of ice should be placed in a tray on the bench to stop any ice cubes dropping onto the floor. Method 2 Warm the water to about 35oC and record the mass of the calorimeter and of the water. Record the start temperature and steadily add dried ice of known mass until the water temperature drops to about 5oC . Calculate the L of fusion for water, accounting for transfer of energy from the water and the calorimeter. Method 1 Wait until the funnel is dripping at a steady rate without the heater on and measure the rate of melting. Put the heater on and calculate the energy transferred by the heater over a measured time. Calculate the rate of melting due to the heater and use this to calculate the l fusion for water.

Estimate the uncertainty in each measurement. Questions Method 2 Measure the mass of an empty copper calorimeter then fill the calorimeter approximately two-thirds full of warm water. The water should be about 15 C warmer than room temperature. Measure the mass of the calorimeter and the water and calculate the mass of water in the calorimeter. Place the calorimeter in an insulation jacket and measure the temperature of the water. Dry an ice cube with a paper towel and add it to the water to reduce the water temperature, allowing the ice cube to melt. Add ice cubes, one at a time, if necessary, to reduce the water temperature to about the same temperature below room temperature as it was initially above room temperature. When the ice in the beaker has melted, measure the water temperature and the total mass of the calorimeter and its contents. Record all your measurements. Results and conclusions Use the measurements of mass to calculate the mass of ice melted, m, and the mass of water, m2, initially in the calorimeter. The thermal energy needed to melt mass m of ice, Q1 = mL, where L is the specific latent heat of fusion for ice. The thermal energy needed to raise the temperature of mass m of melted ice from 0 C to the final temperature T2, Q2 = mcT2 The thermal energy released by the calorimeter in cooling from initial temperature T1 to final temperature T2, Q3 = m1c1(T1  T2), where m1 = mass of the calorimeter and c1 = specific heat capacity of copper ( = 380 J kg1 K1). The thermal energy released by the water in the calorimeter in cooling from initial temperature T1 to final temperature T2, Q4 = m2c2(T2  T1), where m2 = mass of warm water in the calorimeter and c2 = specific heat capacity of water (= 4200 J kg1 K1). Assuming no heat transfer occurs to the surroundings, the gain of thermal energy of the ice = the loss of thermal energy of the calorimeter and the water initially in the calorimeter Q1 + Q2 = Q3 + Q4 Question Use the above equations to calculate Q2, Q3 and Q4 and hence calculate Q1 and so determine the specific latent heat of fusion for ice, L.   Method 1 For this method you will need: a large plastic funnel, two beakers, a suitable low-voltage heater, a clamp and stand, a mercury thermometer, a low-voltage power supply, an ammeter, a voltmeter, a stopwatch, a top-pan balance, a switch and variable resistor, a supply of ice cubes and some paper towels. Clamp a low-voltage electrical heater (switched off) in ice that has been placed in a funnel, as shown in Figure 1. When the rate of melting of the ice is steady, use a dry beaker of known mass to measure the mass of water dripping from the funnel in a fixed time (e.g. ten minutes). Connect the heater into the circuit shown in Figure 1. With the switch closed and the current kept constant, measure the mass of water dripping from the funnel in the same time as before. Use the variable resistor to keep the current constant. Note the reading of the ammeter and voltmeter and record how long the water was collected for. Estimate the uncertainty in each measurement. Questions The mass of ice melted due to the heater is the difference between the mass collected with the heater on and the mass collected with the heater off. Calculate the mass of ice melted due to the heater and the electrical energy supplied to the heater ( = current  pd  time ).   Use your calculation to determine the specific latent heat of fusion ( = electrical energy supplied ÷ mass of ice melted due to the heater).   Estimate the uncertainty in the value you obtained for the specific latent heat of fusion.

Method 3: Latent Heat of Fusion Problem: What is the latent heat of fusion of ice? Procedure: 1. Set up the apparatus. 2. Add 100 mL of water to the beaker and heat to approximately 75°C. Do not boil. 3. Find the mass of one of the insulated cups. 4. Dry one ice cube and add it to the cup. Measure and record the mass of the cup plus the ice cube. 5. Using the beaker tongs, pour the hot water into the second empty cup. Measure and record its temperature. 6. Carefully pour the hot water into the cup containing the ice cube, taking care that no water splashes out of the cup. 7. Stir the mixture gently with the thermometer until all the ice has melted. At that point quickly measure and record the mixture:s final temperature. 8. Find the new mass of the cup and its contents. 9. Under the heading "Calculations", determine and record the following: (a) the mass of the ice cube (b) the mass of the hot water (c) the change in temperature of the hot water (d) the change in temperature of the melted ice water (e) the heat lost by the hot water (f) the heat gained by the melted ice water (g) the heat gained by ice when melting (h) the latent heat of fusion of ice Questions: 1. Compare your value for the latent heat of fusion of ice with the accepted value by determining the experimental error. 2. Why did you dry the ice cube in step 4? 3. List other sources of error in this investigation, and suggest ways to reduce them. Materials: 2 identical insulated cups (styrofoam) retort stand, gauze, ring clamp Bunsen burner (or electric immersion heater) thermometer (0°C – 100°C) 250 mL beaker ' beaker tongs 100 mL graduated cylinder balance ice cube