Introduction
When a volume of 120 ml is divided into equal parts of alcohol and water by mass, the resulting mixture will have half alcohol and half water. This process can be carried out at a temperature of 25 degrees Celsius.

Explanation
To understand the process in detail, let's break it down step by step:

Step 1: Determining the Mass of the Mixture
Since the volume of the mixture is given as 120 ml, and the density of the mixture is not specified, we cannot directly determine the mass. However, assuming that the density of the mixture is equal to the density of water (which is approximately 1 g/ml), we can calculate the mass of the mixture.

Mass of the mixture = Volume of the mixture × Density of the mixture
= 120 ml × 1 g/ml
= 120 g

Step 2: Dividing the Mass Equally
Since we want to divide the mixture into equal parts of alcohol and water by mass, each part will have a mass of 60 g (half of 120 g).

Step 3: Determining the Volume of Alcohol and Water
To determine the volume of alcohol and water, we need to know their respective densities. Let's assume the density of alcohol is ρ1 and the density of water is ρ2.

Volume of alcohol = Mass of alcohol / Density of alcohol
= 60 g / ρ1

Volume of water = Mass of water / Density of water
= 60 g / ρ2

Step 4: Ensuring Equal Volumes of Alcohol and Water
To have equal volumes of alcohol and water, we need to equate the volumes calculated in Step 3.

60 g / ρ1 = 60 g / ρ2

This equation implies that the densities of alcohol and water need to be equal for the volumes to be equal.

Step 5: Temperature Consideration
At a temperature of 25 degrees Celsius, the densities of alcohol and water may vary slightly. Therefore, it is essential to consider the temperature effect on density while performing the calculations.

Conclusion
To divide a volume of 120 ml into equal parts of alcohol and water by mass, we need to determine the mass of the mixture, divide it equally, calculate the volumes of alcohol and water based on their densities, and ensure that the densities are equal for equal volumes. Considering the temperature effect on density is crucial to obtain accurate results.