A2.00 liter plastic container is flexible enough that its volume can change even while it's sealed. if the container has an initial temperature of 25 °c, what will the new volume be if you put it in the freezer, at -4.0 °c? assume the pressure of the air inside remains constant.

Charles law gives the relationship between volume and temperature of gas.
It states that at constant pressure, volume of gas is directly proportional to temperature.
V/T = k
where V - volume , T - temperature and k - constant 

parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
T1 - temperature in Kelvin - 25 °C + 273 = 298 K
T2 - -4 °C + 273 = 269 K
substituting the values in the equation

V = 1.81 L
new volume is 1.81 L