Question

Trial 1: Initial mass: 3.4g, final mass: 3.2g, change in mass: 0.2g. Joules absorbed by water: 3012.5J

Trial 2: Initial mass: 4.1g, final mass: 3.9g, change in mass: 0.2g. Joules absorbed by water: 3,765.6J

1. Given the energy absorbed by the water and the change in smaple mass, determine the energy content in Joules/gram for each sample

2. Convert the two values determined in #2 to energy content in terms of calories/gram. Note: There are 4,186 J in one food calorie

Answer 1

Given:

In Trail 1:

Initial mass = m₁ⁱ = 3.4 g

Final mass = m₁^f = 3.2 g

Change in mass = m₁ = m₁ⁱ - m₁^f = 3.4 - 3.2 = 0.2g

Energy absorbed by water in trail 1 E₁ = 3012.5 J

Energy in 0.2 g of food = E₁

Let E be the energy in 1 g of food.

0.2 g food --------> 3012.5

1 g --------------> ?

By cross multiplication,

E = 3012.5 * 1 / 0.2 = 15062.5 J

Therefore energy content in food in Trail 1 = 15062.5J

In Trail 2:

Initial mass = m₂ⁱ = 4.1 g

Final mass = m₂^f = 3.9 g

Change in mass = m₁ = m₂ⁱ - m₂^f = 3.4 - 3.2 = 0.2g

Energy absorbed by water in trail 1 E₂ = 3765.6 J

Energy in 0.2 g of food = E₂

Let E be the energy in 1 g of food.

0.2 g food --------> 3765.6 J

1 g --------------> ?

By cross multiplication,

E = 3765.6 * 1 / 0.2 = 18828 J

Therefore energy content in food in Trail 2 = 18828J

We know 1 food Calorie = 4186J

? 18828 J

By cross multiplication,

Energy content of food in Cal/gram = 18828/4186 = 4.497 Cal/ g