How many kilocalories are lost when 500 grams of water cools from 185°F to 140°F?

• A. 10 kilocalories
• B. 12.5 kilocalories
• C. 15 kilocalories
• D. 20 kilocalories

Answer: (B)

To determine the number of kilocalories lost when 500 grams of water cools from 185°F to 140°F, it is important to understand how to calculate the heat loss using the specific heat formula. Water has a specific heat capacity of approximately 1 kilocalorie per kilogram per degree Celsius.

First, convert the temperatures from Fahrenheit to Celsius:

• 185°F is approximately 85°C.

• 140°F is approximately 60°C.

Next, calculate the temperature change in Celsius:

• The change in temperature (ΔT) is 85°C - 60°C = 25°C.

Now, using the specific heat equation, the formula to calculate the heat lost (Q) is:

Q = mass (m) × specific heat (c) × ΔT.

Substituting the values:

• Mass of water is 500 grams (0.5 kilograms).

• Specific heat of water is about 1 kilocalorie/kg°C.

• Temperature change (ΔT) is 25°C.

So we have:

Q = 0.5 kg × 1 kcal/kg°C × 25°C = 12.5 kilocalories.

Thus, when 500 grams of water cools from 185°F