Questions

1. which food item gives you the most energy per gram? compare the larger of the two to a snickers bar which has a value of 215 cal in 28 grams.

2. do you think the values are correct, high or low?

3. the pringles box says 28 grams will give you 150 cal. what is your percent efficiency for your lab?

Answers:

See below  

Step-by-step explanation:

1. Most food energy

(a) Pringles

Heat from Pringles + heat absorbed by water = 0

m₁ΔH  + m₂CΔT = 0

1.984ΔH + 100 × 4.184 × 18 = 0

1.984ΔH + 7530 = 0

ΔH = -7530/1.984 = -3800 J/g

(b) Cheetos

0.884ΔH + 418.4 × 13 = 0

ΔH = -5400/0.884 = -6200 J/g

Cheetos give you more food energy per gram.

(c) Snickers

Food energy = 215 Cal/28 g × 4184 J/1 Cal = 32 000 J/g

The food energy from Cheetos is much less than that from a Snickers bar

2. Experimental uncertainty

The experimental values are almost certainly too low.

Your burning food is heating up the air around it, so much of the heat of combustion is lost to the atmosphere.

3. Percent efficiency

Experimental food energy = 3800 J/g

Actual food energy = 150 Cal/28 g × 4184 J/1 Cal = 22 000 J/g

% Efficiency = Experimental value/Actual value × 100 %

                    = 3800/22 000 × 100 %

                    = 17 %