Question

SETUP

In today’s lab we will measure specific heat using a calorimeter. A calorimeter consist of a small metal cup inside a larger metal container, with a lid.  The cups are thermally separated from each other by means of air and a wooden ring, thus reducing the thermal conduction to a minimum.

To keep track of how much water etc. we have, the whole calorimeter will be placed on a digital scale. Make sure to zero the scale before you place the calorimeter on it.

PART 1:  Initial measurements

To better understand our setup, we shall do the first part without any metal at all, but just cold and hot water.  Please perform the following steps.

1. mass of the inner cup of the calorimeter.

     Mass of inner cup:      _____ 62 grams _____

Zero the digital scale, and then place by the calorimeter (both cups + the ring + one thermometer) on top of the digital scale.

2. mass the whole calorimeter

Total mass calorimeter:        ______ 241 grams ________

*Fill the inner cup of the calorimeter with 150 ml of cold water (from the tap in the lab).

3. mass of the calorimeter + the cold water.

Total mass calorimeter + cold water:          ______ 392 grams _________

QUESTION 1:  What is the mass of the cool water?

            Mass of the cold water:           ____________  ___

• Now it’s time to prepare the hot water.  Take the 250 ml glass beaker.

mass of the empty beaker

Mass of empty beaker:          _______ 97 grams ________

• Fill the 250 ml glass beaker with about 150 ml of water.

mass of the beaker + water.

Mass of beaker + water:       _____ 261 grams  ___

QUESTION 2:  Determine the mass of the water in the glass beaker.

            Mass of water in beaker:      ____________  ___

• Place the beaker with water on the heating plate.  Heat the water until its temperature is about 90 °C.

temperature of the cold water inside the calorimeter.

            Temperature cold water:     _____ 22.1 °C __________

temperature of the hot water inside the beaker using the second thermometer. Once you’re done, make sure to remove this second thermometer.

            Temperature hot water:       ________ 90.3 °C _________

• Wear your safety goggles and put the heat-resistant gloves on.  Then pick up the beaker and carefully pour the hot water into the inner cup of the calorimeter, thus combining the cold and hot water.
  Be careful not to cause any splatter!!
• Witness the temperature of the inner cup rise, as the cold water mixes with the hot water.
• After a while, the mixture will reach its highest temperature when it’s at thermal equilibrium.  Record this temperature in the question below.

maximum temperature of the cold/hot water mixture

            Temperature of cold+hot water mixed:      ________ 55.7 °C _________

new mass of the calorimeter including all the water.

            Total mass calorimeter + cold water + hot water:             _____ 551 grams ___

QUESTION 4 How much of the hot water went into the calorimeter?  (This ought to be equal to your answer in Q7, but typically we lose a few grams of water when pouring it into the calorimeter.)

            Mass of the hot water (added to calorimeter):        ____________  ___

Because the inner cup of the calorimeter is made of metal, a significant amount of heat will actually go from the water into this cup. Therefore we cannot ignore the calorimeter.

However, because the specific heat of water is well known to be   J/(kg K),  it is easy to account for the inner cup of the calorimeter.   Shortly after mixing the water, the system (i.e. the water and the calorimeter) will have come to the same temperature .  Because the inner cup of the calorimeter is isolated from its outer cup, heat cannot easily escape from the calorimeter to the surroundings.  Therefore, the total heat added to the system will be zero:

with

• heat gained by cold water, as it goes from    to   

• heat lost by the hot water, as it goes from    to  
                                                                                (and because it’s lost, this term should be negative!)

• heat gained by the inner cup, as it goes from    to  .

QUESTION 13:  Using the equation above, together with J/(kg K) and all the measurements you made, determine the specific heat of the inner cup.  For full credit, show your calculations below.

            Specific heat of inner cup:      ____________  ___

Answer 1