Problem 7 - Chemistry An Atoms First Approach

Question

You may have noticed that when water boils, you can see bubbles that rise to the surface of the water. Which of the following is inside these bubbles? Explain. a. air b. hydrogen and oxygen gas c. oxygen gas d. water vapor e. carbon dioxide gas

Step-by-Step Solution

Answer

The bubbles that form when water boils contain water vapor (option d). This is because when water reaches its boiling point, the liquid molecules gain enough energy to transition into a gaseous state, forming water vapor. The bubbles rising to the surface contain this water vapor.

Step 1: Understanding boiling

When water reaches its boiling point (100 degrees Celsius or 212 degrees Fahrenheit at sea level), its molecules have enough energy to change from the liquid state to the gaseous state. This process is called vaporization. During this process, the liquid water molecules become water vapor, which forms bubbles that rise to the surface.

Step 2: Analyzing the answer choices

Let's go through each of the options to determine which one best describes the content of the bubbles: a. air: It is not air because the boiling process involves the transformation of water molecules into water vapor, not the introduction of air into the water. b. hydrogen and oxygen gas: While water is composed of hydrogen and oxygen atoms (H2O), the boiling process does not break down the water molecules into separate hydrogen and oxygen gas—the molecular structure of the water remains intact. c. oxygen gas: As mentioned before, the boiling process does not break down the water molecules into separate gases. So, it is not just oxygen gas inside the bubbles. d. water vapor: This is the correct answer. When water reaches its boiling point, the liquid molecules gain enough energy to transition into a gaseous state, forming water vapor. The bubbles that rise to the surface contain this water vapor. e. carbon dioxide gas: Carbon dioxide is not a byproduct of the boiling process. It may be present in small amounts in water (from dissolved air), but it is not the primary component of the bubbles formed when water boils.

Step 3: Conclusion

The bubbles that form when water boils contain water vapor (option d), as it is the result of the vaporization process that occurs when water reaches its boiling point.