### Correct Option: A. As pressure increases, volume decreases. ### Detailed Explanation: **Understanding Boyle's Law:** Boyle's Law states that for a given mass of an ideal gas at constant temperature, the pressure (P) of the gas is inversely proportional to its volume (V). This relationship can be mathematically expressed as: \[ P \propto \frac{1}{V} \] or, more commonly, \[ PV = k \] where \( k \) is a constant for a given amount of gas at a constant temperature. **Step-by-Step Explanation:** 1. **Inversely Proportional Relationship:** - The key aspect of Boyle's Law is that pressure and volume are inversely related. This means that if one quantity increases, the other must decrease to keep the product \( PV \) constant. - For example, if you have a gas in a sealed container and you compress it (decrease its volume), the gas molecules have less space to move around. As a result, they collide with the walls of the container more frequently, which increases the pressure. 2. **Constant Temperature:** - Boyle's Law applies only when the temperature of the gas remains constant. This is known as an isothermal process. If the temperature changes, the relationship described by Boyle's Law does not hold. 3. **Practical Example:** - Imagine a syringe filled with air. If you pull the plunger back (increasing the volume), the pressure inside the syringe decreases because the air molecules have more space to move around, leading to fewer collisions with the walls. Conversely, if you push the plunger in (decreasing the volume), the pressure increases. 4. **Graphical Representation:** - If you were to graph pressure (P) against volume (V), you would see a hyperbolic curve. As volume increases, pressure decreases, and vice versa. This visual representation reinforces the inverse relationship. ### Why Other Options Are Incorrect: - **Option B: As pressure increases, volume increases.** - This statement contradicts Boyle's Law. If pressure increases, volume must decrease to maintain the constant product \( PV \). Therefore, this option is incorrect. - **Option C: As volume increases, pressure remains constant.** - This statement is also incorrect. According to Boyle's Law, if volume increases, pressure must decrease (not remain constant) to keep the product \( PV \) constant. - **Option D: As volume decreases, temperature decreases.** - This statement is misleading. Boyle's Law does not directly relate volume and temperature. It only describes the relationship between pressure and volume at constant temperature. If the volume decreases, the pressure increases, but the temperature can remain constant if the process is isothermal. ### Common Pitfalls: - **Confusing Boyle's Law with Charles's Law:** Remember that Boyle's Law deals with pressure and volume at constant temperature, while Charles's Law deals with volume and temperature at constant pressure. - **Ignoring the Constant Temperature Condition:** Always ensure that the temperature is constant when applying Boyle's Law; otherwise, the relationship does not hold. ### Revision Summary: - Boyle's Law states that pressure and volume of a gas are inversely related at constant temperature (PV = k). - As pressure increases, volume decreases, and vice versa. - This law applies only under isothermal conditions (constant temperature). - Remember the distinction between Boyle's Law and other gas laws, such as Charles's Law.