Question

What is the density of water?

Asked by: Richard

Answer

This is a very powerful question. The answer to it tells one a lot about us as a species that interacts with the world. The simple answer is that the density of water is one. That's it! Well, OK, actually I've given you the specific gravity of water. The actual density of water is one gram per milliliter. You can see that the specific heat of a substance is the same as its density without the units.

So, now that you know this, what does it tell you about us as a species? Well, we are the ones who said that the density of water is one gram per milliliter. How did we come to this decision? We had to first decide what a meter is so that we could know what a decimeter is so we could make a liter (a cubic decimeter) and then we could make a millimeter which we could fill with water and call it a gram! So, if you ever find yourself in a desert island you too could make a milliliter by getting a gram of water!

Of course it cannot stay this simple! You have a gram of water in one milliliter only if it is at 4 degrees centigrade. As you know materials expand and contract with temperature. Water's density is one gram per milliliter only at 4 degrees centigrade and at one atmosphere of pressure since pressure also affects the density of liquids.

So, in the end, if you ask what is the density of anything, you have to define its temperature and its location so that we can know the atmospheric pressure.

Answered by: Tom Young, B.A. Science teacher, Whitehouse High School



Although the density of water varies somewhat with temperature and pressure, and is higher for salt water than fresh water, you can use about 62 lb per cubic foot for its weight density in English units.

Water was used as the basis for establishing the metric unit of mass, however, so it is easier to remember that a cubic centimeter of it has a mass of 1 gm. Knowing that there are 1000 cubic centi- meters in a liter, you can also use 1 kilogram (1000 grams) per liter for water's mass density.

Answered by: Mr. Paul Walorski, B.A. Part-time Instructor

Search

Loading


Support Discovery Capsule - Anton's new project on Kickstarter.



Science Quote

'We should take care not to make intellect our god; it has powerful muscles but no personality.'

Albert Einstein
(1879-1955)
Science Sidebar | Science Education Articles
Cool Summer Science Projects

Why not make science a part of your family’s summer? Perhaps you can set aside one day a week for outdoor projects—maybe Mad Scientist Monday or Scientific Saturday? Here are a few ideas to help get you started. Continue reading ...

10 Ways to Keep Your Kids Interested In Science

Young children are natural scientists: they ask questions, pick up sticks and bugs outside, and are curious about the world around them. But as they get a bit older, many kids gradually lose their interest in science. They might see it as just another task at school, something that doesn't apply to their lives. Of course nothing could be further from the truth, so here are ten ways you can remind your kids that science is everywhere. Most of these are fun for adults, too! Continue reading ...

Top Selling

Here are our physics & astronomy bestsellers:
3D Magnetic Field Tube
Space Wonder Gyroscope
KonusScience 5 Way Microscope Kit
Revolving Multi-Color Fiberoptic Light
12 inch Galileo Thermometer
Wood Grain Newtons Cradle
Brush Robot 4M Kit
Solar Radiometer
Tin Can Robot 4M Kit
Periscope

Sponsors

USC University of Southern California Dornsife College Physics and Astronomy Department McMaster University Physics and Astronomy Department