Which law explains gas volume changing with pressure?

• A. Boyle's Law
• B. Charles's Law
• C. Avogadro's Law
• D. Henry's Law

Answer: (A)

The main concept is how pressure and volume of a gas relate when temperature stays essentially constant. For a fixed amount of gas at the same temperature, pressure and volume are inversely related: cranking up the pressure compresses the gas and reduces its volume so that the product P × V remains the same (P1V1 = P2V2). This inverse relationship is exactly what Boyle's law describes, making it the best fit for how volume changes with pressure. The other laws describe different situations: volume changes with temperature at constant pressure (Charles's law), volume changes with the amount of gas at fixed temperature and pressure (Avogadro's law), and gas solubility in a liquid depending on pressure (Henry's law). So, doubling the pressure on a gas at the same temperature will roughly halve its volume, illustrating the inverse relationship.