To determine the order of the samples from greatest to least average kinetic energy of water molecules, we need to understand that temperature is directly related to the average kinetic energy of molecules. The higher the temperature, the greater the average kinetic energy.
By examining the given temperatures of the water samples, we can observe that 88°C is the highest temperature and 21°C is the lowest temperature. Therefore, the sample with 88°C will have the greatest average kinetic energy, and the sample with 21°C will have the least average kinetic energy.
Hence, the list of water samples in order from greatest to least average kinetic energy of the water molecules is:
1. 88°C
2. 40°C
3. 21°C