Experiment: A liquid seems to disappear


Today, we will show you a simple experiment in which a liquid seems to disappear. Do you believe that 2 + 2 is always equals to 4…? Discover this!


  • Distilled water
  • Rubbing alcohol
  • A large test tube
  • A couple of containers

Follow these steps:

  1. First, pour 200 millilitres of distilled water into the test tube. We will do this very carefully so as not to go beyond that amount because the measure must be exact.
  2. We will now do the same with the alcohol. When we have 200 millilitres of the ethyl alcohol, we will pour it into the same glass that holds the distilled water.
  3. When you get to this point you will logically think that there will be 400 millilitres in the glass, right? 200 ml of distilled water + 200 ml of ethyl alcohol = 400 ml.
  4. If we pour the contents of the glass back into the test tube, we will find that… it does not add up to 400 millilitres!

How can that be?

In science, 2 plus 2 is not always equal to 4. What has happened in this experiment is that the volume has contracted. If we were to weigh the mixture on a scale, we would see that the mass has not changed.

This is because water and alcohol molecules interact in a special way. There is strong cohesion between them that draws them close together

This “bonding” brings about a reduction in the volume that we can perceive when we use quantities that are not very small. The greater the quantity we use, the greater will the difference in volume be.


Discovery magazine

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