Does oil and water solution have greater volume than water and alcohol and water and vinegar?Why does water and oil have a greater volume?

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txmedteach's profile pic

txmedteach | High School Teacher | (Level 3) Associate Educator

Posted on

To answer this question, we have to consider something significant for this problem: does one of the given liquids dissolve in the other? If one liquid can dissolve in the other, the two are termed "miscible." If two liquids are miscible, then their respective volumes combine, and the end volume will be significantly less than the original two volumes prior to mixing.

Alcohol and vinegar (acetic acid) are both miscible in water. Alcohol has a hydroxyl (-OH) group that allows hydrogen bond formation and interaction with water. Similarly, acetic acid or acetate, depending on pH, has a carboxyllic acid group, again allowing hydrogen bond formation and miscibility. Therefore, when these two chemicals are mixed with water, the volumes combine so that the resultant volume is significantly less than the two independent volumes.

Oil, on the other hand, is not miscible in water. Depending on the density of the oil, it will either sit on top of the water, or the water will sit on top of the oil. They will not combine in a steady state, though without another chemical added to the mix! The resulting volume when you combine these two mixtures will then be approximately the sum of the two independent volumes. The actual volume will be slightly less because the top liquid will slightly compress the bottom liquid. However, the result is the same: the oil and water mixture has a higher volume than the vinegar or alcohol and water mixtures.

I hope this helps! You could always do an experiment in your kitchen to test this, too!

najm1947's profile pic

najm1947 | Elementary School Teacher | (Level 1) Valedictorian

Posted on

Oil and water are immiscible where as water & alcohol and water & vinegar are miscible liquids.

In missible liquids each liquid is homogeniously mixed and do not make layers or droplet in the other liquid hence there volume is equal to the sum of volumes of both the liquids.

In case of immiscible liquids like oil and water, when the two are mixed, they form layers with a visible meniscus due to difference in their densities. The lighter one, oil in this case, comes to the top and water makes the bottom layer. On agitation, oil breaks down in to droplets and makes an unstable solution called emulsion due to different surface tension. The formation of droplets of oil in water increase the total volume of the total volume of the so called solution as compared to the sum of volumes of individual component namely oil and water.

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