The gas law primarily applied in a spray can is Gay-Lussac's Law.

Here's how it works:

* The Setup: Spray cans contain a product (e.g., paint, hairspray) and a propellant gas, often a compressed gas like butane or propane. The propellant is kept under high pressure within the can.

* The Mechanism: When you press the button, you release the pressure on the propellant. Gay-Lussac's Law states that the pressure of a gas is directly proportional to its absolute temperature when the volume is held constant. As the pressure decreases, the temperature of the propellant also decreases.

* The Result: This temperature decrease causes the propellant to rapidly vaporize. The expanding gas pushes the product out of the nozzle, creating the spray.

In summary: Gay-Lussac's Law explains how the pressure change in the spray can leads to the vaporization of the propellant, which in turn powers the spray.