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Water

Subject: Chemistry
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DETERMINATION OF WATER-SPECIFIC HEAT CAPACITY

The heat capacity can be determined for an arbitrary composite system. In this lab we will investigate the thermal properties of water. If it takes 300 J to raise the temperature of 1 K in a certain amount of water, it takes 600 J to raise the temperature as much in twice the amount of water. This shows that the specific heat capacity of water is proportional to the mass. Which gives:

C = c * m

By combining the expression W = C * T1 - T2, we get W = c * m * (T1 - T2)

We write about and get:

c =
(It is therefore characterized specific heat capacity with the letter: c)

Specific heat capacity thus expresses how much heat is spent to raise the temperature 1K in 1 kg of the substance. An equal amount of heat released when the temperature drops 1K.

SUPPLIES: thermos, immersion heater, thermometer, stopwatch and graduated cylinder.

PERFORMANCE

1st We began by measuring 500 ml of cold water with a graduated cylinder and pour over the water in a thermos. The water had mass 499 g (density of water is 0.998 g/cm3).

2nd After a while, read the temperature with a thermometer to 11.4 0C.

3rd Allowing an immersion heater to heat the water for a number of different time intervals, we measured the size of the temperature difference was in the different cases (T1 - T2).

4th By posting our results, we could then obtain a mean value of the heat capacity. See table.
time in sec heat energy WJ initial temperature, T1 end temp, T2 temp difference mass heat capacity, c
(J / g * level)

300 88 800 10 51 41 499 4.3
540 159 840 10 70 80 499 4.6
194 57 424 11.4 39.3 27.9 499 4.1
660 195 360 10 94 84 499 4.7
mean: 4.4

The average value was determined to be 4.4 J / g * K

We can compare our average with the tabulated value which lies at 4.18 J / g * K.

Sources of error

With the equipment that was used, it was difficult to specify the values ​​to more than two significant digits.

CONCLUSION

We managed quite well with getting a value consistent with tabellväden.

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