Question

An aluminum can of a soft drink is placed in a freezer. Later, you find that the can is split open and its contents frozen.Work was done on the can in splitting it open. Where did the energy for this work come from?

Short answer

The energy required to split the aluminum can open comes from the heat transfer between the soft drink and its surroundings (the freezer), as the soft drink undergoes a phase change from liquid to solid due to the removal of heat. This is possible through the concept of latent heat. The expansion caused by the freezing puts pressure on the aluminum can, eventually splitting it open.

Step-by-step solution

Identify the energy conversions occurring during the freezing process

When we place the aluminum can with the soft drink in the freezer, heat is transferred from the soft drink to the colder surroundings (i.e., the freezer). This heat energy is used to lower the temperature of the soft drink and eventually freeze it.

Determine the source of energy for the work done on the can

The primary source of energy for the work done on the can comes from the previously mentioned heat transfer. When the soft drink inside the can freezes, it expands. This expansion results in an increase in pressure within the can. The increased pressure pushes against the walls of the can, forcing it to expand and eventually split open. Thus, the energy used to split the can open comes from the heat transfer between the soft drink and the surroundings.

Explain the energy transfer process

The energy transfer process can be explained using the concept of latent heat. Latent heat is the energy required to change the phase of a substance without changing its temperature. In the case of the soft drink, as heat is removed from the liquid (due to the colder environment of the freezer), the liquid eventually reaches its freezing point. At this point, the heat removed from the soft drink is used to change its phase from liquid to solid (ice) without changing its temperature. This energy transfer results in the expansion of the soft drink and the splitting of the can.

Summary

In summary, the energy required to split the aluminum can open comes from the heat transfer between the soft drink and its surroundings (the freezer), as the soft drink undergoes a phase change from liquid to solid due to the removal of heat. The expansion caused by the freezing puts pressure on the aluminum can, eventually splitting it open.

Key concepts

Latent Heat

Let's talk about latent heat, a concept crucial to understanding the behavior of substances as they transition between different states of matter. When we cool a can of soft drink in the freezer, it's not just temperature that changes—the drink undergoes a phase change from liquid to solid. Latent heat is the hidden energy involved in making that phase change happen without altering the soft drink's temperature. Think of it like a stealthy energy ninja, working behind the scenes as the drink turns to ice.

During the phase change, the latent heat is released or absorbed. For the soft drink, the freezer environment is colder, so the drink releases latent heat to the surroundings. This process is like the drink 'paying a toll' in the form of energy to become ice. Though the temperature of the drink doesn't go up or down in that moment, its internal energy changes, leading to the freezing expansion we observe.

Heat Transfer

Heat transfer is the next piece of the puzzle when it comes to our freezing can of soft drink. What's really happening? The freezer removes heat from the drink, step by step, lowering its temperature until the drink reaches the freezing point and starts to turn to ice. This process can be likened to a thermal race, where heat energy sprints from the warmer soft drink to the colder freezer air.

There are three main methods by which heat can be transferred: conduction, convection, and radiation. In our aluminum can scenario, conduction is the key player since it involves the direct transfer of heat through materials; here, heat conducts away from the can into the surrounding air. The can and drink inside become cold enough to freeze, demonstrating the powerful effect of heat flowing from a warmer place to a cooler one.

Expansion Upon Freezing

Why does the aluminum can burst? This phenomenon is due to the unique property of expansion upon freezing, which water exhibits. Unlike most substances, water expands when it turns into ice. It's as if each water molecule demands more 'personal space' as they solidify.

As the soft drink, which mostly consists of water, freezes, it expands by about 9%. This might not sound like a lot, but it's enough to exert considerable pressure on the walls of the can. The can, despite being made of metal, has its limits and eventually gives way. This expansion is like a silent but forceful push that causes the can to split open, a dramatic demonstration of the power of expanding ice.

Energy Conversion

When we look at the whole process of cooling and freezing a soft drink, there's a fascinating story of energy conversion unfolding. Initially, the soft drink contains a certain amount of internal energy in the form of heat. As the can cools in the freezer, this heat energy is transferred to the surrounding environment, changing the soft drink's internal energy.

The fascinating bit comes when the drink reaches its freezing point. The heat energy lost doesn't just vanish—it's converted. Here's the key: the energy needed to split the can comes, quite surprisingly, from the energy originally contained within the drink itself. This is the beauty of energy conservation: energy converting from one form, heat, into the work that ultimately enlarges or breaks the can.