The Science Behind Pressure Build-Up in a Yogurt Container: Explained

Have you ever wondered why pressure builds up in a yogurt container when you add warm water and a few drops of dish detergent, seal it, and give it a good shake? This seemingly simple question actually involves a fascinating interplay of chemistry and physics. Let’s delve into the science behind this everyday phenomenon.

The Role of Warm Water

When you add warm water to the yogurt container, it heats the air inside the container. According to Charles’s Law, the volume of a gas is directly proportional to its temperature, provided the pressure remains constant. However, since the container is sealed, the volume cannot increase. Therefore, the pressure inside the container increases instead.

The Role of Dish Detergent

Dish detergent plays a crucial role in this process. When you shake the container, the detergent forms bubbles. These bubbles trap the warm air, preventing it from cooling down quickly. This helps maintain the increased pressure inside the container for a longer period.

The Role of Shaking

Shaking the container serves two purposes. First, it helps mix the warm water and dish detergent, creating more bubbles to trap the warm air. Second, it agitates the air inside the container, causing it to heat up further due to friction. This additional heat contributes to the increased pressure inside the container.

Why Doesn’t the Pressure Decrease Immediately After Shaking?

After you stop shaking the container, you might expect the pressure to decrease immediately as the air cools down. However, this doesn’t happen because the bubbles created by the dish detergent act as an insulator, slowing down the cooling process. As a result, the pressure inside the container remains high for a while even after you stop shaking it.

What Happens If You Open the Container?

If you open the container while the pressure inside is still high, the sudden decrease in pressure causes the bubbles to burst, releasing the trapped warm air. This can result in a small explosion of foam, similar to what happens when you open a shaken can of soda.

In conclusion, the pressure build-up in a yogurt container when you add warm water and dish detergent and shake it is a result of several factors: the heating of the air by the warm water, the trapping of the warm air by the bubbles created by the dish detergent, and the agitation of the air by shaking. This simple experiment is a great way to demonstrate some basic principles of chemistry and physics in a fun and engaging way.