Mandatory Experiments: Heat Flashcards
General Heat: Accuracy points for all experiments. (4)
-Lag the calorimeter and use insulating lid to reduce heat loss to the surrounding air.
-Avoid very large rises in temperature as this causes large heat loss to the surrounding air.
-Use a sensitive thermometer with low specific heat capacity to get a precise value of the temperature rise.
-Try to arrange the experiment so that room temperature is about half way between the initial and final temperature of the liquid and calorimeter. This way the heat loss to the surrounding air at the end of the experiment is approximately equal to the heat gain from the surrounding air at the start of the experiment.
ME 1: Specific Heat Capacity by electrical method: Formula? Describe how measurements found?
E = m(l)c(l)delta T(l) + m(c)c(c)delta T(c)
Measure and record mass of calorimeter, liquid and initial temperature of both.
Allow the current to flow for five minutes and record the electrical energy supplied by using the joulemeter.
Measure and record final temperature with thermometer
ME 2: Specific Heat Capacity by mechanical method: Describe how the copper was heated and how its temperature was measured? Explain why adding a large mass of copper would improve the accuracy of the experiment. Formula.
Copper in test tube placed in beaker of water which is heated with bunsen burner.
Place thermometer in water to measure temperature of copper pieces.
When water is 100 degrees wait a few minutes to allow copper to reach the same temperature than transfer the copper pieces to the calorimeter.
Larger mass of copper means smaller percentage error in calculations.
Heat loss of copper pieces = heat energy gain of liquid in calorimeter + heat energy gain of calorimeter.
ME 3: Specific Latent Heat of Fusion of Ice: Why was the ice crushed? Why was the ice dried? How was the ice crushed? How was the ice dried?
To ensure all ice was the same temperature of 0 degrees
To ensure that only ice was added to the calorimeter
Pestle and mortar
Using a towel
ME 3: Specific Latent Heat of Fusion of Ice: Describe how the mass of added ice was measured. Why use warm water? Why use melting ice?
(Mass of calorimeter + water + melted ice) - (mass of calorimeter + water)
So that temperature rise of melted ice is larger and a larger temperature rise results in smaller percentage errors.
To ensure that the ice was at 0 degrees.
ME 3: Specific Latent Heat of Fusion of Ice: State two characteristics of a thermometer suitable for use in this experiment. Formula.
Low specific heat capacity.
Graduated to 0.1 degree Celsius.
Heat to melt ice + heat to warm melted ice = heat loss of warm water + heat loss of calorimeter.
ME 4: Specific Latent Heat of Vaporisation of Water: State two assumptions made about the polystyrene cup. How was the water cooled below room temperature? How was the steam dried?
That it is a perfect insulator
That is has a negligible heat capacity
Use of ice.
Use of a steam trap as a tilted insulated delivery system.
ME 4: Specific Latent Heat of Vaporisation of Water: How does dry steam and cool water increase accuracy in the experiment?
Calculations assume that only steam is added.
Heat energy gained = heat energy lost
ME 4: Specific Latent Heat of Vaporisation of Water: Why is the calculated answer not accurate? (3). Formula.
Thermometer not sensitive enough, lack of insulation, heat loss/gain to the surrounding area.
Heat emitted as steam condenses + heat emitted as boiling water cools = heat gain of cold water + heat gain of calorimeter
