Kinetic and Thermal Energy Quick Check

Question

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Question
A fisherman in a boat is drinking a cup of hot coffee. The large lake below his boat is full of cold water. Which statement is an accurate comparison of the lake water and the coffee?(1 point)
Responses

The lake will have more total thermal energy, and the particles in the lake water will be moving faster.
The lake will have more total thermal energy, and the particles in the lake water will be moving faster.

The coffee will have more total thermal energy, and the particles in the coffee will be moving faster.
The coffee will have more total thermal energy, and the particles in the coffee will be moving faster.

The coffee will have more total thermal energy, but the particles in the lake water will be moving faster.
The coffee will have more total thermal energy, but the particles in the lake water will be moving faster.

The lake will have more total thermal energy, but the particles in the coffee will be moving faster.

Answer 1

To answer this question, we need to distinguish between "total thermal energy" and the average kinetic energy of the particles (which is related to temperature).

1. Total thermal energy is a measure of the total energy of all the particles in a substance, which depends on both the temperature and the amount (mass) of the substance.
2. Average kinetic energy relates to the temperature of the substance; higher temperature means faster-moving particles.

In this scenario:

• The lake water, being large in volume, contains a far greater mass of water than the cup of coffee. Thus, the total thermal energy of the lake, despite its lower temperature, will be much higher than that of the coffee.
• The coffee, being hot, will have particles with higher average kinetic energy (and hence higher temperature) compared to the colder particles in the lake water.

Based on the analysis above, the accurate comparison is:

The lake will have more total thermal energy, but the particles in the coffee will be moving faster.