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"Burning" Calories: Tin Can Calorimetry
Most people have read nutrition labels to see how many calories are in their food, but do we all know what a calorie is?
Scientifically speaking, a kilocalorie (the type of calorie we use to measure energy contained in food) is the energy needed to raise the temperature of 1 kilogram of water by 1 degree Celsius.
If you can convert the chemical energy contained in food into heat energy, then you can watch (and calculate) the calories in the food being released in real time! In this activity, learners will discover what calories are by monitoring and tracking their effects on a can of water.
Follow along with our Discovery Place scientist in the video and find a detailed materials list with instructions below!
Age Range: 10+ years old
Prep Time: 10-15 minutes
Learning Time: 45-60 minutes
- A responsible adult
- Pencil to write with
- Copies of Burning Calories Activity Sheet
- A long glass or meat thermometer (a long glass thermometer or meat thermometer works best, but not a medical thermometer)
- Metal can (a soda can with tab still attached will be the easiest!)
- Measuring cup
- Large paperclip
- Cork or wad of clay
- Wooden rod or another pencil
- Ring stand or another object to suspend the can between (like two equal stacks of books)
- Foods to test (high-fat foods like cheese puffs, walnuts/peanuts, buttered popcorn and potato chips burn best; melty foods like chocolate do not work and just make a mess!)
- Tweezers or tongs
- Calculator (if needed/desired for calculations)
- Fire extinguisher or spare cup of water nearby for emergencies
- Set up a safe environment for the experiment. Clear the area of any items that may be flammable and make sure small children and pets are not nearby. An adult should always be present and be the one handling the fire/hot can.
Note: Some foods and can coatings will smoke when exposed to heat! This experiment is best done outside to avoid setting off smoke detectors.
- Make copies of the activity sheet linked above and gather all other materials.
- Pour 100 mL of water into the can (100 mL is equal to 0.42 cups). Record the volume of liquid as 0.1 liters in the first column on the activity sheet – assume that it remains constant throughout the experiment.
One kilogram of water is more or less equivalent to 1 liter. Remember that one kilocalorie is the amount of energy required to raise the temperature of 1 kilogram of water by 1 degree Celsius, so it is easiest to use simple fractions of 1 liter to do this calculation!
The more water in the can, the more heat will be required to show a significant change. While you may choose to use a different fraction of a liter if you want, you will see less temperature change the more water you add.
- Stand the tab up on the top of the can, then feed the wooden rod or pencil through the hole at the top. If you are using a vegetable or soup can without a tab, an adult can punch holes through the metal at the top of the can.
- Suspend the can by balancing the ends of the rod on a ring stand or on another stable and even platform so that the can is a few inches off the ground.
- Place the end of the thermometer in the water in the can and turn it on. After setup is complete and the thermometer has had time to get an accurate reading, record the temperature in Celsius.
If your thermometer only uses Fahrenheit, record the numbers in Fahrenheit, then convert by using an online converter or this formula: Celsius (°C) = (Fahrenheit - 32) ÷ 1.8
- Unfold one end of the paper clip and stick it firmly into the cork or mound of clay. Straighten out the other end somewhat to form a small platform where food samples can be placed.
Set the cork/clay beneath the tin can while making sure there is room (but not much!) between the can and the top of the paperclip. The goal is to have the food item as close to the bottom of the can as possible while still having enough space to fit the tip of the lighter to catch the food on fire.
- Choose the first food you would like to test and place one nut/chip/puff/etc. on the platform of the paper clip. It might help to bend the end of the paperclip into a skewer of sorts to stab into the food to hold it in place.
- Once the setup is secured and the first measurements have been recorded on your activity sheet, have an adult use the lighter to light the food on fire! Depending on what you choose, some food will burn easier than others. Keep relighting the food until it is entirely charred/burned.
- Carefully stir the water with the thermometer (the can might be hot!), then record the updated temperature once the temperature stops changing.
With this method, some heat will be lost to the environment and the calculations will not be perfect, but you should still see some change in temperature.
- Use tweezers or tongs to pick up and discard the burned food sample (be careful of the hot paper clip!), then add a new sample to the stand. Make sure the platform is still positioned directly beneath the bottom of the can.
- Record the new starting temperature before continuing the experiment, then repeat steps 9-12 until you have tested all the food samples.
After you finish your experiment, remove the thermometer from the water. Carefully discard any used items (burnt food, bent paperclip, can, etc.) that you cannot reuse – you may want to run them under cold water first. Put away your other materials and then crunch some numbers to determine how many calories you just burned!
The more foods you test, the more data you can gather. And the more calculations you can do, the more you can learn!
- Once you finish your calculations, compare your results to the nutrition labels. Divide the number of calories by the number of pieces per serving to determine the calories per item.
- Ex: A bag of potato chips has 200 calories per serving
- One serving is 10 chips
- 200 calories ÷ 10 chips = 20 calories / chip
- Each chip has an average of 20 calories
- Compare these numbers to the numbers that you calculated for each item. Are they close? How far off are they?
While this experiment is not perfect and may not yield precise results, the calorie number we see on the food label can have an error margin of up to +/- 25%! So, if there’s a big difference between your calculations and the nutrition labels, don’t automatically assume that your results are the ones that are wrong!