How many British thermal units (Btu) are needed to raise 10 lbs of water from 33 degrees F to 43 degrees F?

To calculate the number of British thermal units (Btu) needed to raise the temperature of water, you can use the formula:

Btu = weight of water (in lbs) × temperature change (in degrees F).

First, determine the temperature change. The initial temperature is 33 degrees F and the final temperature is 43 degrees F. The difference is:

43 - 33 = 10 degrees F.

Next, use the weight of the water, which in this case is 10 lbs. Now, plug these numbers into the formula:

Btu = 10 lbs × 10 degrees F = 100 Btu.

This means that you need 100 Btu to raise 10 lbs of water from 33 degrees F to 43 degrees F, making the correct choice.