Why does tap water boil at < 100° C?

Question

I noticed that in a school science experiment the water boiled at 90°, what causes this?

Answer 1

Minerals dissolved in tap water disrupt the intramolecular hydrogen bonding of the water, lowering the strength of these bonds. Since the strength of hydrogen bonding is directly related to boiling point, this is why. Also, by disrupting the intramolecular bonding, the vapor pressure of the water is increased, because now the force holding the water molecules together is lessened; therefore, the water will turn into vapor easier.

Answer 2

It depends on high your altitude is, although a boiling point of 90 degrees seems very low.

If the atmospheric pressure is low, such as at a high elevation, then the bloiling point will be lower. So in a mile high city such as Denver or Mexico City, it is very possible for water to boil at 90 degrees.

Don't forget to check the accuracy of your thermometer and the barometric reading for the day.

Answer 3

Either the thermometer is faulty, or your school is high enough above sea level for water to boil at 90 C.

Answer 4

At lower atmospheric pressure the boiling point decreases.

One of the colligative properties is boiling point elevation, not depression. Therefore impurities are not likely to cause a boiling point depression.

Answer 5

Tap water has added minerals that are soluble in water. These minerals have a lower boiling point than does pure water and thus lowers the water that it is in.

Answer 6

Minerals in the water - boiling point depression - look it up in your chemistry book.

http://www.newton.dep.anl.gov/askasci/chem03/chem03005.htm

Answer 7

Altitude - most likely