Question

Why does a sealed bag of chips expand when you take it to a higher altitude?

Short answer

The bag of chips expands at a higher altitude because the external air pressure decreases, causing the internal pressure to push outward and expand the bag.

Step-by-step solution

Understand Air Pressure

Air pressure decreases as altitude increases. This is because the density of the air decreases with height, which means there are fewer air molecules exerting pressure on objects.

Relationship Between Pressure and Volume

According to Boyle's Law, for a given amount of gas at a constant temperature, the pressure and volume are inversely proportional. This means when the pressure decreases, the volume of gas increases.

Observe the Effect on the Bag

A sealed bag of chips contains a fixed amount of gas inside. When you take it to a higher altitude, the external air pressure decreases.

Conclusion

As a result of the lower external pressure, the air inside the bag exerts more relative pressure to the outside. This causes the bag to expand, since the internal pressure pushes against the declining external pressure.

Key concepts

Air Pressure

Air pressure is the weight of the atmosphere pressing down on the Earth's surface. It is the result of air molecules colliding with surfaces and each other. As you go higher in altitude, the air becomes thinner. This means there are fewer air molecules above you.
Since there are fewer molecules to collide, the pressure is lower. The relationship between altitude and air pressure is straightforward: the higher you go, the lower the pressure becomes. This is important when you think about sealed objects like a bag of chips. At higher altitudes, the bag will experience less pressure from the outside.
Hence, understanding air pressure helps explain why certain phenomena, such as the expansion of a sealed bag, occur.

Altitude

Altitude refers to the height above sea level. As altitude increases, the layer of air becomes thinner. Essentially, you have fewer air molecules around you as you go higher. Because air pressure is determined by the weight of the air pushing down on you, higher altitudes mean lower pressure.
For instance, at sea level, the air pressure is about 101.3 kPa, but this pressure decreases as you move to higher elevations, such as mountains. This change in air pressure with altitude is crucial for understanding how gas behaves in sealed containers. Higher altitudes exert less external pressure on the container, explaining why sealed bags tend to expand.

Gas Volume

Boyle's Law is fundamental to understanding how changes in pressure affect the volume of gas. This law states that for a given amount of gas at constant temperature, the pressure and volume are inversely proportional. This means that if pressure decreases, the volume of the gas increases, and vice versa.
For example, if you have a sealed bag of chips, the amount of gas inside it is fixed. When you take it to a higher altitude where the external pressure is lower, the gas inside expands. The internal pressure of the gas exerts more force against the bag since the external force is less, causing the bag to inflate.
In summary, gas volume increases as external pressure decreases, which is a direct application of Boyle's Law. Understanding this relationship helps explain why sealed containers like bags of chips expand when taken to higher altitudes.