According to the ideal gas equation (PV = nRT), if the pressure is doubled while keeping the temperature and the amount of gas constant, the volume will be halved.

Here's why:

* P: Pressure

* V: Volume

* n: Number of moles of gas (constant)

* R: Ideal gas constant

* T: Temperature (constant)

Since n, R, and T are constant, we can simplify the equation to:

P₁V₁ = P₂V₂

If P₂ = 2P₁, then:

P₁V₁ = 2P₁V₂

Dividing both sides by 2P₁:

V₁/2 = V₂

Therefore, V₂ = V₁/2, meaning the volume is halved when the pressure is doubled.