by Oksana Love
Downloads: Download Article (PDF)
Question to Investigate
Will adding mint or chile flakes change the temperature of water?
Introduction
We all love the fresh and cool feeling in our mouth when we chew a minty gum or brush our teeth with toothpaste. Mint is one of the herbs that gives us this feeling … specifically, the chemical menthol that is found in mint. But what exactly is happening? And does menthol actually affect the temperature of our tongue?
You’ve probably also noticed the opposite effect when you eat spicy foods. In many cases, spicy peppers (and chile flakes or chile powder that are made from them) can make foods taste “hot.” When food is very spicy, we feel warm, and a sensation of “burning” is created in our mouth.
So, does chile powder really increase the temperature of our tongue? In this experiment, we will look into how mint and chile powder affect the temperature of water.
Safety Suggestions
- Safety goggles required
- Protective clothing suggested
- Caution: hot liquids
- Do not eat or drink any of the materials used in this activity
- Thoroughly wash hands after this activity
Safety First! Read the Science Safety Tips to find important practices for kids and chemists to do before, during, and after every chemistry activity.
Materials
- 2 clear glasses
- Mint toothpaste (can also replaced with mint chewing gum or mints/mouth fresheners containing menthol)
- Chile powder (can be replaced with paprika)
- Water
- Digital thermometer
- Watch/timer
Procedure
- Add one cup (240 mL) of water to both glasses (labeled Glass A and Glass B).
- Measure the temperature of the water in each glass. Record the temperatures in the table below.
- Add 1 tablespoon (about 5 mL) of mint toothpaste into one glass (Glass A) and approximately 1 tablespoon (15 g) of chile powder into the other (Glass B). Carefully stir the water to dissolve the toothpaste and chile powder in their respective cups.
- Wait for 10 minutes and record the temperature of the water in each glass in the table below.
What Did You Observe?
| Cup with Mint Toothpaste | Cup with Chile Powder | |
| Initial temperature (water only) | ||
| Final temperature (after 10 minutes of mixing in toothpaste/chile powder) |
How Does it Work?
Were you surprised that there was no change in temperature in the water when you added the “cool” mint and the “hot” chile powder? Since the water temperature stayed the same, what do you think gives the cooling effect in mint, and the warming effects in spicy foods?
Menthol is the chemical found in mint, and capsaicin is the chemical found in chile. Both molecules have unique abilities to “fool” the temperature sensors on our tongues. When this happens with menthol, it gives a sensation in our mouth that’s similar to eating ice cream, while capsaicin causes a burning sensation. So, the “cooling” and “heating” effects are because the chemicals are tricking our tongues!
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