Waters of the Earth
Concept: Most of the water on Earth is salty and is found in oceans. Freshwater
can be found in rivers, lakes, glaciers, ice sheets, underground, in clouds, in the
air, and in living things. (75 minutes, inside, Internet, hands-on)
Materials
• Plastic bottles: half‐liter, liter, two‐liter
• Small graduated container: beaker, graduated cylinder, or test tube
• Funnel
• Bucket or pitcher
• Water supply
• STEM journal
Engage
Hold up a glass or beaker of water and ask students where they got there last
drink of water from. Can they trace that last drink back to where on Earth the water
might have originated? What are some of the sources of water on Earth? How
much (what fraction) of the water on Earth comes from the various sources you
mentioned?
Explore
Have students use this interactive:
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.waterdist/global
-water-distribution/. It requires a free registration to access. If you have a computer
and video projector available, you could show and go through the interactive with
the students as a whole. If you are not able to project the site to the group, you
could get a sense of the scales involved, copy the information, and write the
different amounts of water on the board or chart paper. Note that there are
discussion questions and background information on this Web site.
To make these numbers more meaningful and sensible to students, try the
following activity after you have presented the interactive or the information.
1. Gather as many liter (or two-liter) soda bottles as possible; the more the
better. You could also use half-liter water bottles, if those are more accessible
in quantity. Assemble the other materials in the list also.
2. Display a small beaker, a small graduated cylinder, or a test tube filled with
10 mL of water. Tell students this amount represents the water available for
all humans on Earth whose primary source is a river. The table below
displays the scaled quantities of other sources of water on Earth.
3. Have students help you fill up a half-­‐liter water bottle or a 500 mL beaker, if
available. Display this to represent the amount of fresh surface water
(lakes, swamps, and rivers) on Earth.
Water Source Rivers (drinking water for humans) Fresh Surface Water All Fresh Water on Earth Earth’s Water Scaled Quantity 10 mL = .01 L 500 mL = .5 L 165 L 5,500 L 4. Continue by having students help filling up as many of the liter, or half-­‐liter,
bottles as you have available. If you can find stand-­‐in objects (marbles,
paper clips, stones) to make up 165 items/liters, all the better. These will
represent all the fresh water (icecaps, glaciers, groundwater, other, and
surface water) on Earth.
5. Finally, devise a way to add items to the number of full water bottles you
have, to model 5,500 items/liters. This could be boxes of paper clips (100),
beads, or dots printed on sheets of computer paper.) With this visual, you
now have a scaled representation of all the water on Earth.
6. To help students bring all of this together, you could refer to the discussion
questions found on the Web site for the interactive above.
Extend
If there is time available, students can extend their exploration of the topic with the
following resources:
• Challenge students to calculate the volume that 5,500 liters of water would
occupy.
• Have students compare 5,500 liters of water to the average amount of
water each American uses daily.
Additional Background Information
• Summary of the Water Cycle:
http://water.usgs.gov/edu/watercyclesummary.html
• How much water is there on, in, and above the Earth:
http://water.usgs.gov/edu/earthhowmuch.html