chemistry lab

Unit 5 Lab: Caloric Content of Food

CHEM 1806

Purpose: To practice using thermodynamic data and calculations to determine the caloric content of food.

Materials: Student Supplied –lighter or candle, Al foil or tray, Food items (marshmallows, nut of some sort, chips or popcorn), water, fork or small skewer for holding food

LabPaq materials: 100 mL glass beaker, burner stand, digital scale, test tube clamp, thermometer

Procedure:

1. Record the mass of the clean, empty 100-mL beaker. (Record below)

2. Place approx. 50mL of water in the beaker and mass it again. (Record below)

3. Place the burner stand on top of the Aluminum foil.

4. Place the beaker of water on top of the burner stand and record the temperature of the water. (Remember to record to appropriate sig figs!)

Marshmallow (or other sugary, light, candy)

1. Mass the marshmallow and the fork or skewer you will use, record.

2. With the marshmallow on the fork or skewer, light it with a candle or lighter.

3. As soon as it is burning well, hold the marshmallow under the beaker of water while stirring gently with the thermometer.

4. Record the final temperature of the water.

5. Mass the remaining marshmallow residue and fork / skewer. Record.

6. Replace the water with fresh water and prepare for the Nut.

Nut (or other high protein, high fat food)

1. Mass the nut and record.

2. A nut is held best with the test tube holder. Light the nut. It might take a few minutes to really get it lit.

3. Follow the same procedure as with the marshmallow (#’s 3-6)

Other food (whatever you have)

1. Mass another food.

2. Follow the same procedure as with the marshmallow (#’s 2-5)

(8 pts) Data Table:

	Marshmallow	Nut	Other:
Mass of Beaker
Mass of Beaker + water
Mass of Water
Initial temp. of water
Mass of food item
Mass of holder
Final temp of the water.
Change in temperature.
Mass of food residue remaining
Change in mass
Q = t*m*cp
Heat energy per gram
Convert to kilocalories

Results and Discussion:

Complete the table above, for each food.

(8 pts) Provide one set of calculations below. (For example, show all of the calculations required for the marshmallow.)

For Q, multiply the change in temperature of the water by the mass of the water and heat energy gained by the water (in J). cp = 4.184 J/g C)

To calculate the heat energy per gram, divide Q by the change in mass of food. Change in mass of food = initial mass of food – final mass of food.

(4 pts) Insert a picture of your charred food.

When you are finished, save the file as LASTNAME_Food and upload it to the Dropbox for Unit 5 Labs.