實驗中的比潛熱比標準較高,點解?

Question

請寫出誤差..及解釋誤差。

我想問水珠係發熱棒上面...點解會提高比潛熱?

Answer 1

As you didn't give a description of your experiment, I could only assume that you estimated the specific heat capacity (of water, say) by a simple experiemnt of measuring the temperature rise of water after a known amount of heat was given to it.

The equation for the estimation of specific heat capacity is:
Q = m.c.T
where Q is the known heat given
m is the mass of water with specific heat capacity c
T is the rise in temperature of water

Thus, c = Q/m.T

The basic assumption in the experiement is that heat loss to the surroundings and heat used to heat up the vessel used in the experiement are both negligible. That is, it assumes all the heat supplied are used to heat up the water, the rise in temperature of water should, therefore, be higher than what is actually recorded in the experiment.

If T' is the temperature rise recorded in the experiment, and T is the expected temperature when all heat supplied is used to heat up the water, obviously, T > T'

The specific heat capacity estimated from experiment c' = Q/m.T'
whereas the expected specific heat capacity c = Q/m.T

Since both Q and m remain the same in the two wquations,
thus c' > c

2006-12-09 16:21:31 補充：
similar reason for water droplets on the heater. Heat energy is used to vaporize the water droplets instead of heating up the water in the experiment.

Answer 2

heat lost to surrounding