Tema 02 - Energia, Calor e outros Conceitos | Experimentos - Expansão adiabática

Summary

This experiment demonstrates the effects of pressure and temperature changes on a gas inside a sealed container. Using a thermometer, a spray bottle with alcohol, a rubber stopper, and a PET bottle with a small hole, the experiment shows how injecting air increases pressure, raising the internal temperature. When the stopper is quickly released, the temperature drops significantly, causing alcohol vapor to condense into white mist, similar to cloud or fog formation. The rapid changes in pressure and temperature illustrate the principles used in refrigeration systems like air conditioners and refrigerators.

Takeaways

• 😀 The experiment uses a thermocouple, alcohol spray, a tire pump, a rubber stopper with a valve, and a PET bottle with a small hole.
• 😀 The thermocouple wire is inserted through a rubber stopper in the bottle to measure the internal temperature.
• 😀 Alcohol vapor is sprayed into the bottle to help visualize condensation during the experiment.
• 😀 Injecting air into the bottle using the tire pump increases the internal pressure and raises the temperature.
• 😀 The volume of the bottle remains constant during air injection, leading to an increase in internal pressure and temperature.
• 😀 When the pressure is suddenly released by removing the stopper, there is a rapid temperature drop and condensation forms a white mist.
• 😀 The white mist forms due to the condensation of alcohol vapor as the temperature decreases after rapid decompression.
• 😀 This process of sudden temperature drop and condensation is similar to cloud formation or fog on cold days.
• 😀 Repeating the compression process increases the temperature and causes the mist to disappear.
• 😀 The experiment demonstrates an adiabatic process, where there is no heat exchange between the system and its surroundings.
• 😀 The principles of pressure, temperature, and condensation demonstrated in the experiment are applied in refrigeration systems like refrigerators and air conditioners.

Q & A

What is the purpose of using the thermocouple in this experiment?

The thermocouple is used to measure the internal temperature of the bottle before and after the transformation caused by compressing and decompressing the air inside the bottle.

Why is alcohol sprayed into the bottle?

Alcohol is sprayed into the bottle to generate vapor. This vapor helps visualize condensation during the experiment, as it forms a white mist when the temperature drops.

How does the compression of air inside the bottle affect its temperature?

When air is compressed inside the bottle, its pressure increases while the volume remains constant, causing the internal temperature of the bottle to rise.

What happens when the rubber stopper is suddenly removed?

When the rubber stopper is abruptly removed, the pressure inside the bottle decreases, leading to a rapid expansion of the gas. This causes a significant drop in temperature, resulting in the formation of visible mist.

What is an adiabatic transformation?

An adiabatic transformation occurs when the gas expands or compresses without exchanging heat with the surroundings, leading to changes in temperature due to internal energy variations.

Why does the temperature drop when the air expands rapidly?

The temperature drops because the energy required for the expansion comes from the internal energy of the gas, which decreases as a result, causing the temperature to fall.

How does the formation of mist relate to the temperature change?

As the temperature decreases during the gas expansion, the alcohol vapor condenses, forming a visible mist. This happens because colder temperatures cause the vapor to transition into liquid form.

What is the connection between this experiment and natural phenomena like cloud formation?

The experiment simulates the process of condensation that occurs when warm air rises, cools, and forms clouds. In both cases, a temperature drop causes water vapor or alcohol vapor to condense into liquid droplets.

What effect does repeating the compression have on the mist and temperature?

When the air is compressed again, the temperature inside the bottle increases, causing part of the mist to dissipate as the alcohol vapor returns to its gaseous form.

How is the principle demonstrated in this experiment related to refrigeration systems?

The principle of compressing and decompressing a gas to change its temperature is used in refrigeration systems, such as refrigerators and air conditioners, where gases are compressed to increase their temperature and then expanded to cool down, facilitating heat transfer.