Uploaded by gregory mills

L.FoodCalorimetry (1)

advertisement
Name: ____________________________________________ Date: ____________________________ Period: _______
Still Trying to Survive that Zombie Apocalypse – A Food Calorimetry Lab
INTRODUCTION:
Plants have evolved processes that convert light energy into the chemical bonds of complex molecules. The
chemical bonds in carbohydrates, fats, and proteins store energy until needed by the plant. The plant can then
release the energy by breaking the appropriate chemical bonds.
Every animal maintains its life processes by consuming complex molecules that store energy. The
processed plants and animals we eat as foods contain varying amounts of proteins, carbohydrates, and fats.
Because each of these types of foods contains varying amounts of energy, these foods will release varying amounts
of energy when they are used by cells. Within our bodies, the energy is released slowly by a series of chemical
reactions.
By burning pieces of food, the chemical energy stored in molecular bonds is released as heat and light. The
heat can be measured in units called calories. A calorie is the amount of heat (energy) required to increase the
temperature of one gram of water by one degree C. This process is the basis of the technique of calorimetry.
The more calories a food contains, the more heat is given off when burned. Foods high in calories will
release large amounts of energy. One gram of a protein will release far fewer calories than one gram of fat.
You will see how much energy (calories) food releases.
WHAT IS A CALORIMETER? HOW DOES A CALORIMETER WORK?
A calorimeter (calor =Latin for heat) is a device that measures the heat generated by a chemical reaction,
change of state, or formation of a solution. There are several types of calorimeters but the main emphasis of all
calorimeters is to insulate the reaction to prevent heat loss.
We will be using a homemade calorimeter. A particular food item will be ignited, the homemade calorimeter
will trap the heat of the burning food, and the water above will absorb the heat, and cause the temperature (T) of the
water to increase. By measuring the change in temperature (ΔT) of a known volume of water, you will be able to
calculate the amount of energy in the food tested because the heat gained by the water will equal the heat lost by
the food item.
ESSENTIAL QUESTIONS
1. Predict: How do these food items rank according to their energy content (from the highest to the
lowest):
2. Predict: Which food would you want to stockpile in case of a zombie apocalypse, and why?
MATERIALS
Goggles
Graduated Cylinder
Glass Ring stand
Wire Gauze
Food Samples
Balance
Thermometer
Lighter
Candle
Watch
Rings – 2
Soda Can
PROCEDURE
1. Tie hair back and put on goggles. Hair must be up and
goggles must be on for the entire lab, because fire.
2. Gather all materials. Assemble the set-up apparatus as
diagramed to the right. The watch glass + food sample
should be as close to the can as possible (<5 cm) when
the set-up is finalized.
3. Measure the mass of the food sample and record the mass in Data Table 1.
4. Measure out approximately 100.0 mL of water (measure the exact amount – remember: doubt! – And
record in Data Table 1) in the graduated cylinder, then put the water into the soda can.
5. Put your thermometer in the soda can and measure the temperature – remember: doubt! – and record
the temperature in Data Table 1 as initial water temperature.
6. Place the food sample onto the watch glass. Place the sample on the table away from the calorimeter.
7. Light the candle on fire. You will be using the candle to light all of your food samples on fire for the
entire lab, so keep the candle light and someone should be in charge of watching the candle (safety
rule #1 – don’t leave a flame unattended!)
8. Using the candle, light the food on fire and immediately move the sample under the calorimeter. Let the
sample burn itself out completely. If it goes out before the food is burnt to a black crisp, relight it
immediately.
9. As soon as the food sample is completely burned, measure the temperature of the water again and
record in Data Table 1 as final water temperature. Be sure to watch the thermometer carefully, to
catch the highest temperature reached.
10. Find the mass of the sample remaining and record in Data Table 1 as mass of sample after burning
(ash weight).
11. Repeat procedure for another sample of the same food (use new water!). You should have 2 trials of
the same food.
12. To make sure you get an accurate amount of data, record your average data on the class data table in
the front of the classroom. Copy the class data into Data Table 2.
DATA & ANALYSIS
**Fun Fact** The density of water is 1.00 g/mL. When you measure the volume of the water (in mL) it converts
to mass in grams at a 1:1 ratio.
Density = Mass
Volume
so…
so…
Mass = Density x Volume
Mass = 1.00 g x Volume (mL)
mL
Data Table 1: ___________________________________________________ Date: ____________________
Food
Sample
Mass of
food before
burning (g)
Mass of food
after burn (g)
Change in
Mass of
food (g)
Initial
Temp of
Water (°C)
Final Temp
of Water
(°C)
[Col 2 – Col 3]
Change in
Temperature
of Water (°C)
Exact Mass
(Volume) of
water used (g)
[Col 6 – Col 5]
Trial 1
Trial 2
Average
X
X
X
X
Data Table 2: ___________________________________________________ Date: ____________________
Food Sample
Change in Mass
of food (g)
Change in Temp of
Water (°C)
Exact Mass (Volume)
of Water used (g)
Energy in food
sample (Q)
So how can we calculate the amount of energy in a food item?
The energy lost by the food
burning will be absorbed in to the water. To calculate the energy in the food sample, we will calculate the
amount of energy the water absorbed using Q = mCΔT. We are assuming that all the energy released by the
Cheetos puff was transferred to the water in the can.
Q is the heat (energy) gained in kilocalories – food calories (Cal)
m is the mass of water in grams (g)
C is the specific heat capacity of water (0.001 Calorie/g °C)
ΔT is the change in temperature in degrees Celsius (°C)
Show an example calculation for one of the food samples:
Q = mCΔT
Example Calculation:
Complete the final column in Data Table 2.
Can we directly compare the energy of the food samples?
No. We need to take into consideration the mass of food sample that was burned.
Show an example calculation for one of the food samples:
□ Take the two Q values from Data Table 2 for one food sample. Find the average.
□ Take the two Change in Mass of Food values from Data Table 2 for the same one food sample.
Find the average.
□ Divide the Average Q by the Average Mass. Record in the Analysis Table.
Example Calculation:
Analysis Table:
Food Sample
Average Energy in
Food Sample (Q)
Average Change in
Mass of food (g)
Energy in Food Sample Per Gram
(Calorie/g)
[Divide Column 2 by Column 3]
Conclusion Questions
1. What type of energy transformation do we see when we burn the Cheetos puff (what type of energy
does the puff have, and what does it turn into when we burn it)?
2. On a separate sheet of paper, draw a diagram of the process. Draw in arrows showing where energy is
transferred. Name one place where you see each type of energy transfer (radiation, convection, and
conduction).
3. Do you think the number of Calories you calculated is likely to be lower or higher than it really is?
Explain why.
4. Examine the Nutritional Value Information found on the package of your assigned food sample. Use
this information to determine the “accepted value” for the heat content per gram of that snack food.
Accepted Value: ____________________________
What is the percent error for your experiment? (Use the Energy in Food Sample Per Gram for your
assigned sample as your measured value)
5. Give 2 examples of how you could improve the accuracy of this experiment. (Explain your error)
6. On a separate piece of paper, with your group, design an experimental set-up that would allow for
better data collection. Draw and label a picture of your new design.
7. Which food would you want to stockpile in case of a Zombie Apocalypse?
Claim: ____________________________________________________________________________
Evidence: _________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
Reasoning: ________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
Download
Random flashcards
State Flags

50 Cards Education

Countries of Europe

44 Cards Education

Art History

20 Cards StudyJedi

Sign language alphabet

26 Cards StudyJedi

Create flashcards