You could use a scale to measure the mass as well as a cup to hold the water. If you were comparing the two, you should also probably use a graduated cylinder to get the same amount of each type of water.
Hope this helped ^_^
Answer:

Explanation:
First of all we need to calculate the heat that the water in the cooler is able to release:

Where:
- Cp is the mass heat capacity of water
- V is the volume
is the density


To calculate the mass of CO2 that sublimes:

Knowing that the enthalpy of sublimation for the CO2 is: 


Density = 1.01 g/cm^3 or 1.01 kg/dm^3 or 1010 kg/m^3
Density = mass/volume = 1010 g/1000 cm^3 = 1.01 g/cm^3 = 1.01 kg/dm^3
= 1010 kg/m^3