specific heat capacity?

Question

a 42.6 gram lead fishing weight is removed from a boiling water bath and allowed to cool to room temp (25.0 C) calculate the heat involved in kilojoules. (waters specific heat capacity is 4.184 j/gC)

not sure if i need to multiply the specific heat by 100 to make it kilos. but my answer was 13370000kj. could someone check?

Answer 1

Q = mc(delta T)
Where Q is the heat energy lost by the fishing weight, c is the specific heat of the lead the weight is made from, and (deltaT) is the change in temperature experience by the fishing weight.

You are given mass as 42.6 grams.

You are told that the specific heat of water is 4.184 J / grams degree C, but this is irrelevant since it is the lead weight that is cooling, not the water. Did the problem state the specific heat of water, or did you look that value up on your own and put it into the question? (I suspect the latter)

The specific heat of Lead is: .1286 Joules per gram degree C.

The change in temperature the Lead experiences is calculated to be 75 degrees C (= 100 degrees when in the boiling water - 25 degrees after cooling to room temperature).

You now know all the information you need.

Q = mC(delta T)
Q = (42.6 g)(.1286 J / g degree C)(75 degree C)
Q = 410.9 Joules

You are asked for the Energy value in kilojoules, not Joules, so to convert, divide by 1000.
Q = .4109 kJ is released by the Lead.


EDIT:
You should be able to tell just by looking at your answer that it is wrong. An energy value of 13370000 kJ is HUGE. That is an incredible amount of energy. There is no way such a tiny piece of lead could absorb that much energy from the water without melting/vaporizing first, so as to release it into the room.

Answer 2

You don't have the right information. The fishing weight has to transfer its heat to something else, such that you can measure the heat taken up by something else, by the temperature change in something else. For example, the fishing weight in boiling water is supposedly 100C when you take it out. It has so many cal of heat and weighs 42.6g. Maybe drop it into a known amount of water at a low temperature and measure the higher temperature once the fishing weight has heated up the second bit of water.

Answer 3

Heat = mass * specific heat * change in temperature

And, boiling water has a temperature of 100 C.

You should be able to do the rest!

- A chemistry teacher

Answer 4

Make a simple compare about your blood count. Those who have more will less vulnerable to dry cold.