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Q & A: Liquids more dense than water or alcohol

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Q:
Which liquid is more dense water or Alcohol?
- Larry (age 46)
Old Dominion University, Norfolk, VA
A:
Well, I cannot speak for all kinds of alcohols, but the common ones (methanol, ethanol, and isopropyl alcohol) are a little less dense than water. All three of these have densities of about 0.79 g/cc at standard temperature and pressure, compared to 1.0 g/cc for water.

Lots of liquids are more dense than water or the three different alcohols mentioned.

Mercury is a liquid at room temperature and has a density of 13.6 times that of water (careful, mercuryís poisonous). Most metals, when melted, will be heavier than water (but may be hotter than water will tolerate), such as molten lead or steel (leadís also poisonous!).

Glycerol (or Glycerin) is more dense than water (1.26 g/cc).

One could argue that glass is a very slow-moving, viscous liquid (although it has lots of properties of a solid, like rigidity). Itís more dense than water.

Even saltwater is more dense than water. By how much depends on how much salt youíve dissolved in it.

Tom

(republished on 07/25/06)

Follow-Up #1: Alcohol/Water density difference

Q:
how to you perform an experiment to see if alcohol is less or more denser than water?
- bob carey (age 15)
annapolis, maryland, united states
A:
Hello Bob,

There is a device called a hydrometer that is used to measure the density of liquids.  Basically it is a small glass vial, with a bit of weight in the bottom, that will float in the liquid.   Depending on the density of the liquid it will float higher or lower.   The height, read out on a calibrated scale, allows one to determine the density.  

A very simple test that you can do to measure the relative density of alcohol and water is to  stick a tiny weight on the end of a toothpick or pencil that makes the buoyancy such that it doesn't sink.   Then measure the relative heights that it floats in alcohol and in  water.  

LeeH




(published on 08/20/07)

Follow-up on this answer.