It makes sense that most people blow on hot soup or tea to prevent burning themselves.

A stronger blow allows the hottest molecules to escape more quickly, allowing you to enjoy your beverage at the ideal temperature more quickly.

You can wait for your cup of coffee or plate of chili to cool down. But will blowing on a hot meal or beverage actually make it colder, or are you just fooling yourself?

Blowing on Hot Food Helps to Cool It Down

Blowing on hot food can occasionally be a little embarrassing, particularly when you’re in a fancy restaurant and everyone in the place is watching you cause food flecks to fly through the air. Fortunately, those efforts weren’t in vain because cooling food and beverages down with a fan does work.

When you blow on hot food, your cooler breath replaces the hot air released from the food through a process called convection, consequently cooling down the food. According to ThoughtCo, the cycle repeats itself constantly, with the hot air from the food being replaced by the cool air from your breath. According to BBC Science Focus, stirring hot drinks can speed up convection, which causes hotter liquid to rise to the surface and cool more quickly.

Blowing on hot items also pushes away vapor clouds that form over hot drinks and moist food, replacing warm, damp air with dry, cool air, explains BBC Science Focus. According to ThoughtCo, this quickens evaporation, allowing more water vapor in beverages or on moist food to turn into gas and hasten to cool as heat energy is transferred from the object to the air.

Heat Transfer from Conduction and Convection?

Your breath is close to body temperature (98.6 degrees Fahrenheit), but hot food is much hotter. The rate of heat transfer is directly proportional to the temperature difference, which explains why this is significant.

Moles are propelled by thermal energy. The movement of the first molecule can be decreased and the movement of the second molecule increased by transferring this energy to other molecules.

The process continues until all the molecules have the same energy (reach a constant temperature). Your food would lose energy (become colder) if you didn’t blow on it because the energy would be transferred to the air molecules and container around it (through conduction), while the air and dishes would gain energy (become warmer).

The effect happens faster when there is a large difference in the energy of the molecules, as in hot cocoa, cold air, or ice cream on a hot day. The opposite is true when there is a small difference, as in hot pizza on a hot plate or a chilled salad at room temperature. Either way, the process is relatively slow.

When you blow on food, the situation is altered. Convection is the movement of relatively cooler air where previously heated air was present. This increases the energy difference between the food and its surroundings and allows the food to cool more quickly than it would otherwise.

What Happens When You Blow on Hot Food?

Your breath is close to the average body temperature, which is 98.6 degrees Fahrenheit (per ThoughtCo.). However, hot food has a temperature higher than this. When you blow on your food, the colder air from your body temperature goes to where the hot air was previously, which is known as “convection.” When you blow on hot food, you are making it colder, just as there are inventive ways to cool down spicy food.

So that you can avoid burning your mouth, science may help you better understand the factors that make food or beverages cool off more quickly. When there is a large contrast between “the energy of the molecules,” such as holding a hot cup of green tea on a cold day or a snow cone on a summer day, the temperature change will occur more rapidly than if there is a minor contrast — think warm pasta on a warm dish or “a refrigerated salad at room temperature.”

According to a different ThoughtCo article., thermal energy is “heat energy” that illustrates a contrast in temperature “between two systems.” For example, human beings and a warm cup of coffee have thermal energy. This energy can be compared with “the [surrounding] environment.” But in both cases, the changes happen fairly slowly. Blowing on hot food generally expedites the process because it causes a greater energy contrast between the food and its surroundings, which causes the food to cool more quickly.

What is the Most Effective Way to Cool Food?

The fastest and safest way to quickly cool food is through a two-stage cooling process.

The food must be divided into smaller portions, covered loosely while cooling, stirred with an ice paddle, or placed in an ice bath, and then refrigerated until it reaches 41°F or lower.

Adding ice cubes to food can also help cool it down quickly, but this should only be done for recipes that would not be watered down by added ice cubes. Additionally, using an ice paddle to stir food can aid in internal cooling without diluting the final product.

Read More: How Long Can Frozen Food Stay in the Car

Conclusion

Because of its high temperature and humidity, your breath is actually a pretty poor gas to use to effectively cool coffee. Try blowing from the front of your mouth rather than pushing air out of your throat to get the most out of your effort. (I’m not sure how much of that makes sense, but musicians are frequently told to do it in order to alter their tone. When you blow from the front of your mouth, like you’re whistling, the air is cooler and drier than when you breathe from the back of your throat, like when you yawn.)

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