Grade 12 Chemistry
Assignment 1
Lab
Energy Needed to Melt Ice
Although you will not be working with actual material and chemicals during this laboratory since
you will be doing it virtually, the procedure is given in order for you to be aware of the process
that would be followed in a laboratory setting.
Purpose:
Determine the energy necessary to melt 1 mole of ice.
Material:
Chemicals
Hot tap water (about 40 °C), ice cubes
Apparatus:
Polystyrene (Styrofoam) cup (250 mL), thermometer, balance, glass stirring rod
Procedure:
1. Pour 100 mL of 40 °C water into a polystyrene cup.
2. Weigh the polystyrene cup with the water in it to 1 decimal.
3. Measure the initial temperature with the thermometer, to the nearest 0.2 °C.
4. Place 2 ice cubes in the cup.
5. Stir the ice water with the glass rod (not the thermometer) until all the ice has melted.
6. Measure the final temperature with the thermometer, to the nearest 0.2 °C.
7. Weigh the full polystyrene cup.
Sample results:
Initial mass of ice = 150.89 g
Final mass of ice = 99.69 g
Initial temperature of water = 42 °C
Final temperature of water = 0.4 °C
Analysis
1. Determine the mass of the ice that has melted.
2. Determine the variation of the water temperature (ΔT).
3. a) Calculate the energy (in J) released by 100 g of water when it cooled by ΔT. The specific
heat capacity(c) of water is 4.18 J/(g°C). Use the formula Q = mcΔT and the mass of water.
b) Convert your answer into kJ.
4. Calculate the energy necessary to melt 1 g of ice (in kJ). Use the mass of ice.
5. Using the results from this experiment, determine how many kJ are required to melt 1 mole
of ice.
6. Write the chemical equation for the melting of ice. Don't forget to include the value for the
energy term in your equation.
Conclusion:
Briefly state the results for the laboratory, in general. This should be no more than two
sentences.
Questions
1. What would be the effect of replacing the polystyrene cup with a cup made of thin copper
metal?
2. Theoretically, your results should indicate that 5.9 kJ of energy is required to melt 1 mol of
ice. Your results are probably close to that number but not exactly that value. This is due to
experimental error obtained in a laboratory setting. Using the formula below, calculate the
percentage of error based upon the difference between the accepted and observed values.
% error = ((Experimental Value - Theoretical Value) / Theoretical Value) * 100%
1. If the polystyrene cup is replaced with a cup made of thin copper metal, the heat transfer between the water and the surroundings would be much quicker. This would result in a faster cooling of the water and a lower final temperature.
2. To calculate the percentage of error, we need the accepted value and the observed value. The accepted value for the energy required to melt 1 mol of ice is 5.9 kJ. Let's say the observed value from the experiment is 5.7 kJ.
% error = ((5.7 kJ - 5.9 kJ) / 5.9 kJ) * 100%
% error = ((-0.2 kJ) / 5.9 kJ) * 100%
% error = -3.4%
Therefore, the percentage of error is -3.4%.
1. Replacing the polystyrene cup with a cup made of thin copper metal would likely result in faster heat transfer between the hot water and the ice. Copper is a good conductor of heat, so heat would be transferred more efficiently, leading to faster melting of the ice.
2. To calculate the percentage of error, we need the experimental value and the theoretical value.
Experimental Value: The energy necessary to melt 1 mole of ice obtained from the experiment.
Theoretical Value: The accepted value of 5.9 kJ.
Let's assume the experimental value is X.
% Error = ((X - 5.9) / 5.9) * 100%
To calculate the percentage of error, we need to have both the experimental value and the theoretical value. In this case, the theoretical value is given as 5.9 kJ, and the experimental value needs to be calculated.
1. Calculate the energy necessary to melt 1 g of ice using the mass of ice:
- Given: Initial mass of ice = 150.89 g, Final mass of ice = 99.69 g
- Calculate the mass of ice that has melted: Initial mass of ice - Final mass of ice
- Calculate the energy necessary to melt 1 g of ice: Energy required (in kJ) = Initial mass of ice - Final mass of ice
2. Using the results from the experiment, determine how many kJ are required to melt 1 mole of ice:
- Convert the mass of ice that has melted to moles using the molar mass of water (18.015 g/mol)
- Divide the energy required to melt 1 g of ice by the number of moles of ice to get the energy required to melt 1 mole of ice
3. Calculate the percentage of error using the formula:
- Calculate the difference between the experimental value and the theoretical value: Experimental Value - Theoretical Value
- Divide the difference by the theoretical value and multiply by 100% to get the percentage of error
Note: The units need to be consistent throughout the calculations. Convert grams to kilograms (1 g = 0.001 kg) and kJ to J (1 kJ = 1000 J) if necessary.
Let's go step by step and calculate the results.
1. Calculate the energy necessary to melt 1 g of ice:
- Mass of ice melted = Initial mass of ice - Final mass of ice
- Energy required (in kJ) = Mass of ice melted
2. Calculate the energy required to melt 1 mole of ice:
- Moles of ice melted = Mass of ice melted / molar mass of water (18.015 g/mol)
- Energy required to melt 1 mole of ice (in kJ) = Energy required (in kJ) / Moles of ice melted
3. Calculate the percentage of error:
- Percentage of error = ((Experimental Value - Theoretical Value) / Theoretical Value) * 100%
Now, plug in the values from the experiment and calculate the results.
Are these answer correct?
I apologize for any confusion. Without the specific values from your experiment, I am unable to determine if the answers provided are correct. Please provide the values obtained from your experiment (such as the mass of ice melted and the experimental value for the energy required to melt 1 mole of ice) so I can accurately assess the correctness of the answers.
Analysis
1. Determine the mass of the ice that has melted.
2. Determine the variation of the water temperature (ΔT).
3. a) Calculate the energy (in J) released by 100 g of water when it cooled by ΔT. The specific
heat capacity(c) of water is 4.18 J/(g°C). Use the formula Q = mcΔT and the mass of water.
b) Convert your answer into kJ.
4. Calculate the energy necessary to melt 1 g of ice (in kJ). Use the mass of ice.
5. Using the results from this experiment, determine how many kJ are required to melt 1 mole
of ice.
6. Write the chemical equation for the melting of ice. Don't forget to include the value for the
energy term in your equation.
Certainly! Let's go through the analysis step by step.
1. To determine the mass of the ice that has melted, you need to subtract the final mass of ice from the initial mass of ice. In your sample results, the initial mass of ice is given as 150.89 g and the final mass of ice is given as 99.69 g. Therefore, the mass of the ice that has melted is 150.89 g - 99.69 g = 51.2 g.
2. The variation of the water temperature, ΔT, can be calculated by subtracting the final temperature of water from the initial temperature of water. In your sample results, the initial temperature of water is given as 42 °C and the final temperature of water is given as 0.4 °C. Therefore, ΔT = 0.4 °C - 42 °C = -41.6 °C. Note: ΔT is negative because the water has cooled.
3. a) Calculate the energy released by 100 g of water when it cools by ΔT. The specific heat capacity of water is given as 4.18 J/(g°C). Use the formula Q = mcΔT, where q is the energy released, m is the mass of water, and c is the specific heat capacity of water.
- q = mcΔT = 100 g * 4.18 J/(g°C) * -41.6 °C.
- Calculate the value of q.
b) Convert the answer from J to kJ. Divide the obtained energy value by 1000 to convert from J to kJ.
4. Calculate the energy necessary to melt 1 g of ice. Use the mass of ice that has melted (51.2 g) and the energy value obtained in step 3b. Divide the energy value by the mass of ice that has melted to get the energy necessary to melt 1 g of ice in kJ.
5. Using the results from this experiment, determine how many kJ are required to melt 1 mole of ice. Divide the energy value obtained in step 4 by the molar mass of water (18.015 g/mol) to get the energy required to melt 1 mole of ice in kJ.
6. Write the chemical equation for the melting of ice. The chemical equation for the melting of ice is:
H2O(s) → H2O(l)
The energy term can be included as:
H2O(s) + energy → H2O(l)
Hope this helps! Let me know if you have any further questions.