### Correct Option: B. The volume decreases as pressure increases ### Detailed Explanation: **Understanding Boyle's Law:** Boyle's Law states that for a given mass of gas at constant temperature, the volume of the gas is inversely proportional to the pressure applied to it. This relationship can be mathematically expressed as: \[ P \times V = k \] where: - \( P \) is the pressure of the gas, - \( V \) is the volume of the gas, - \( k \) is a constant for a given amount of gas at a constant temperature. This means that if the pressure increases, the volume must decrease to keep the product \( P \times V \) constant, and vice versa. **Step-by-Step Explanation:** 1. **Inversely Proportional Relationship:** - If you increase the pressure on a gas (for example, by compressing it), the gas molecules are forced closer together, which reduces the volume. - Conversely, if you decrease the pressure (by allowing the gas to expand), the volume increases as the gas molecules have more space to move around. 2. **Constant Temperature:** - Boyle's Law applies only when the temperature remains constant. If the temperature changes, the behavior of the gas will not follow Boyle's Law, and other gas laws (like Charles's Law) may need to be considered. 3. **Practical Example:** - Imagine a syringe filled with air. If you push the plunger down (increasing the pressure), the volume of air inside the syringe decreases. If you pull the plunger back, the pressure decreases, and the volume of air increases. 4. **Graphical Representation:** - If you were to graph this relationship, plotting pressure (P) on the y-axis and volume (V) on the x-axis would yield a hyperbolic curve, indicating that as one variable increases, the other decreases. ### Why Other Options Are Incorrect: - **Option A: The volume increases as pressure increases** - This is incorrect because it contradicts the fundamental principle of Boyle's Law. Increasing pressure compresses the gas, leading to a decrease in volume. - **Option C: The volume remains constant regardless of pressure** - This option is also incorrect. It suggests that the volume does not change with pressure, which is not true according to Boyle's Law. The volume must change to maintain the constant product of pressure and volume. - **Option D: The volume decreases and then increases with pressure** - This option implies a non-linear relationship that does not exist under Boyle's Law. The relationship is strictly inverse; volume cannot decrease and then increase with pressure at constant temperature. ### Common Pitfalls: - **Confusing Boyle's Law with Other Gas Laws:** Remember that Boyle's Law specifically deals with pressure and volume at constant temperature. Other laws, like Charles's Law, deal with volume and temperature. - **Ignoring Temperature:** Always ensure that the temperature is constant when applying Boyle's Law. If the temperature changes, the relationship will not hold. ### Revision Summary: - Boyle's Law states that the volume of a gas is inversely proportional to its pressure at constant temperature. - Increasing pressure results in a decrease in volume, and decreasing pressure results in an increase in volume. - The relationship can be expressed mathematically as \( P \times V = k \). - Always remember that this law applies only when temperature is held constant.