- Author: Rhett Allain. Rhett Allain Science
- Date of Publication: 10.30.14. 10.30.14
- Time of Publication: 8:31 am. 8:31 am

# What Can You Do With All That Halloween Candy?

VStock/AlamyIt’s Halloween time. In the USA, this is traditionally a time of costumes, the beginning of the Christmas decorations, and tons of crappy candy. Oh, you think I’m not a big fan of Halloween? You are correct. The costumes are cool, but the candy is excessive (and the Christmas decorations this early drive me crazy).

I’m not sure what you do when you get annoyed. For me, I blog about things. So let’s get right to the candy.

### How Much Candy Do You Have?

Maybe the answer is “none”. However, if you are like me there are two sources of Halloween candy. First, there is the loot the kids bring home. Second, there is the left over candy that is distributed to the kids that come to our door. If you are really strategic, you can do what we sometimes do. Typically one neighborhoods in the area will have “Trick or Treat” on an earlier day. Send the kids to this neighborhood to collect candy and then give this candy out on Halloween. Yes, you might consider that cheating. I consider it “recycling”.

I’ve looked at the candy at the end of a run through the neighborhood. It might be 2 kg worth of stuff ranging from bubble gum to those hard sugar candies to things like the snack sized Snickers. Let me stick with the 2 kg estimate for the total mass and I will use the “fun size” Snickers as my typical candy (although this might not be typical). Looking at the Snickers website, I get the following info about the fun sized bar.

- 2 bars are a serving (seems like a lot) with a mass of 34 grams.
- For these two bars, it’s 160 Calories.

Assuming the candy wrapping is minimal, this 2 kg of candy would be equivalent to 117 fun sized Snickers and 9,360 Calories.

But what about the energy? Yes, Calories is a unit of energy—it’s just not a very good unit in physics. First, you should know that there is the calorie and then there is the Calorie. The calorie is the amount of energy needed to raise one gram of water by one degree Celsius. The Calorie is 1000 calories. Yes, that’s silly—but it’s true.

If we want to change units, 1 Calorie is equal to 4200 Joules. What’s a Joule? If you push some object with a force of 1 Newton and the object moves 1 meter, that would require 1 Joule of work. Yes, that sort of sucks as a definition. What about this? If you take a gallon of milk from the floor and put it in the refrigerator, that would take about 30 Joules of work.

Assuming a 100 percent efficiency from candy to energy, 2 kg of candy would be 39 million Joules (3.9 x 107 J). Now, what could you do with all this energy?

**Pull Ups.**

Instead of looking up the energy required for a pull-up, I am going to estimate it. Essentially in a pull up, you start from rest and end up at rest but about 30 to 40 cm higher. Let me just assume that all of the energy in a pull up goes into an increase in your gravitational potential energy. This means that for a person with a mass of 70 kg, your change in potential energy would be:

If you were a robot, you could then possibly get this enegy back when you return to your starting position (sort of like regenerative braking for cars). But alas, you are a human. It also requires you to use energy to go back down too. How much? Who knows. Let me just estimate that the whole pull up (up and down) is 340 Joules. Yes, I ignored the change in speed as you go up and down—it’s just an estimate.

If each pull up requires 340 Joules, with 2 kg of candy you could do **115 thousand pull ups.** Yup.

**Charge your phone.**

I’ve looked at the energy in smart phone batteries before. The iPhone 5s has a battery with around 2.14 x 104 Joules. Suppose there was some way that your phone could eat all this Halloween candy. How many times could your phone? That’s pretty simple. I have 39 million Joules divided by 21 thousand Joules and I get 1822 times. If you charged your phone once a day, this candy would **last for about 5 years**. Of course, in 5 years you will have collected EVEN MORE Halloween candy.

**What if your car ran on candy instead of gasoline?**

I bet you have a reasonably efficient car. Maybe it gets 30 mpg. Gasoline has an energy density of about 32.4 MJ/L. This means that one gallon of gas would have 122 MJ (mega Joules) of energy. Ignoring all the inefficiencies of your car, I could say that your car uses 4 MJ per mile (you can check the caclulations for homework).

Now put the 2 kg of candy in your specially adapted car. Running on just this candy, the car **could go 9.75 miles**. That’s far enough for a trip to the grocery store to get some more candy. I wonder which is cheaper per mile, gasoline or candy? I guess the only way to answer this is to estimate the price per Joule for candy.

Let’s do gasoline first. If gas costs $3 per gallon, that is $3 per 122 MJ or 40.7 MJ per US dollar. What about candy? Here is a bag of snickers (Amazon) with a price of $12.20 and a mass of 0.298 kg. That would be a total energy (based on my estimate above) of 5.8 MJ. This would give it a price density of 0.47 MJ per US Dollar. So, stick with gasoline. It’s cheaper—unless you get the candy for free.

### Halloween Candy Homework

I think you have an idea of the things you can do with Halloween candy. Here are some other things you can consider for homework.

- What is the volume energy density for candy?
- Make a plot of energy per mass for different candy brands and types.
- How long could you run your house on 2 kg of candy? Assume you can get your household consumption down to 3 Kilowatts.
- What if you make a rocket that was only powered by candy? If the mass of the rocket was also 2 kg, could 2 kg of candy fuel get it into space? How high could it go? You can ignore air resistance.

One last thing. You can organize your candy-loot and see if you can find any patterns or relationships. I think this is what my daughter was doing last year.

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