How many Joules are needed to condense 35 g of water at 100 oC?
The correct answer and explanation is:
To calculate the energy required to condense 35 g of water at 100°C, you need to use the formula for heat transfer during a phase change, specifically during condensation. The formula is: Q=m×LQ = m \times L
Where:
- QQ is the heat released (in Joules),
- mm is the mass of the substance (in grams),
- LL is the latent heat of condensation of water (in Joules per gram).
The latent heat of condensation for water is the same as the latent heat of vaporization, which is approximately 2260 J/g at 100°C. This is the amount of energy required to convert 1 gram of water from a gas to a liquid without changing its temperature.
Given:
- m=35m = 35 g,
- L=2260L = 2260 J/g.
Now, substitute the values into the formula: Q=35 g×2260 J/gQ = 35 \, \text{g} \times 2260 \, \text{J/g} Q=79,100 JQ = 79,100 \, \text{J}
So, 79,100 Joules of energy are released when 35 g of water condenses at 100°C.
Explanation:
When water vapor cools down and condenses, it releases energy because the molecules transition from a high-energy gaseous state to a lower-energy liquid state. The heat released during this process is known as the latent heat of condensation. This amount of energy is specific to the substance involved and is needed to overcome the forces between molecules in the gaseous phase without changing the temperature of the substance.
In practical terms, the energy released in this case can be used to heat the surrounding environment or to do work in processes such as steam engines or refrigeration cycles.