Unknown Metal Lab

Purpose: To find the specific heat of an unknown metal.

Materials:

Water
Hot plate
Metal tongs
Temperature Probe
Scale
Calorimeter
Glass cup
Metal Substance

Procedure:

First, weight the metal substance and record it’s mass. Then weigh the cup, first without water and then with the room temperature water. This data will be used later in the calculations. Next, add water into glass cup and and calorimeter. Place the glass cup on the hot plate. Leave the water on hot plate until boiling. Measure temperature and record it. Next, place the metal substance in the boiling water. The water will probably stop boiling. Wait until the water begins boiling again and reaches the same temperature as it was before the metal object was placed in the water. Measure the temperature of the water in the calorimeter. Place the metal substance in the calorimeter. Allow cooling until the temperature ceases to change and record this temperature.

Data:

Uncertainty: +/- 0.0005

Uncertainty: +/- .5

Data Analysis:

The specific heat formula is as follows:

c = Q/(m*(change)T)

c: is the specific heat. Units: J/(kg*K)

Q: is the heat. Units: J

(change)T: is the Change in temperature. Units: K

To solve for the specific heat, this equation must be set equal to Q, as shown below:

Q = c*m*(change)T

Next, the heat of the metal and the heat of the water are set equal to each other, and the equation can be solved with the information gathered:

-Qm = Qw

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Data:

Uncertainty: +/- 0.0005

Uncertainty: +/- .5

Data Analysis:

The specific heat formula is as follows:

c = Q/(m*(change)T)

c: is the specific heat. Units: J/(kg*K)

Q: is the heat. Units: J

(change)T: is the Change in temperature. Units: K

To solve for the specific heat, this equation must be set equal to Q, as shown below:

Q = c*m*(change)T

Next, the heat of the metal and the heat of the water are set equal to each other, and the equation can be solved with the information gathered:

-Qm = Qw

-cm*mm*(change)Tm = cw*mw*(change)Tw

-cm(0.0493kg)(299.65K-369.45K) = (4186J/(kg*K))90.1362kg))(299.65K – 296.75K)

-cm(0.493kg)(-69.8K) = 1653.3863J

-cm(-3.4411kg*K) = 1653.3863J

/-3.4411kg*K /-3.4411kg*K

cm = 480.4819 J/(kg*K)

Conclusion:

The specific heat of the unknown metal found through the lab process is

480.4819 J/(kg*K). A metal with a specific heat closest to this was found to be manganese. The specific heat of manganese is 480 J/(kg*K). This is only about .5 of a difference.

One source of error can be found in the measurement of the heat of the metal. This is because it is possible that it did not heat up to the same temperature as the boiling water, creating an uncertainty.

Another source of error can be found in the determined equilibrium temperature. This is because it is possible that the temperature found is before or after equilibrium.

A source of uncertainty is the measurement of temperature with the temperature probe. It is labeled that the temperature probe has a uncertainty of +/- .5K.

Another source of uncertainty is the measurement of mass. The scale could have been zeroed out incorrectly, or simply not exactly centered. This creates an uncertainty of 0.0005 kg.

Another source of uncertainty is through the assumption that no heat was lost to either the cup or air. This would have skewed the data in the calculations and create a lower specific heat.

One way to improve this experiment would be to heat up the metal for a longer period of time. This would ensure that the metal is the exact temperature as the boiling water, thus making the temperature measurement more accurate. Another way to improve this would be to constantly measure the temperature of the water after the hot metal is placed in the calorimeter. This would allow for the student to watch the temperature and more accurately determine when it reaches thermal equilibrium. Furthermore, the loss of heat to the cup or air could be taken into account, creating a more accurate specific heat.