Practical: Energy Content in Food Flashcards

All 5 cards in this deck

What is calorimetry used to measure in food?

The energy content of the food, found from the temperature rise of water heated by burning the food.

What are the steps to measure the energy content of a food sample by calorimetry?
e.g. burning a 1 g crisp under a tube of water

1. Measure the mass of food and the mass of water, and the starting temperature.
2. Burn the food under the water until it stops burning; stir and record the highest temperature.
3. Calculate the energy transferred, then divide by the mass of food to get energy per gram.

What is the formula for the energy transferred to the water in a calorimetry experiment?

Energy (J) = mass of water (g) $\times$ temperature rise (°C) $\times$ 4.2

How do you calculate the energy content of a food per gram?
e.g. 4200 J transferred by a 2 g sample

Divide the energy transferred by the mass of food burned: $4200 \div 2 = 2100$ J/g.

True or false? Heat lost to the surroundings makes the measured energy content of a food lower than its true value.

True. Not all the energy released reaches the water, so the calculated value is an underestimate.