Students
will identify different types of bodies of water such as lakes,
rivers, seas, oceans, and using world maps, identify them
as salt or fresh water sources. The maps will also allow them
to compare the volume of each type of water available globally.
Have students differentiate between the
bodies of water by either researching themselves or providing
descriptions / examples for them: bay, canal, gulf, lake, ocean,
pond, river, stream. See definitions provided in glossary (see
below).
Provide students with a copy of a world
map and have students label the larger bodies of water: Atlantic
Ocean, Pacific ocean, or name the 5 Great Lakes. Have students
colour global salt water sources in red, frozen sources in orange,
and fresh water sources in blue. Highlight a few for them: Salt
water - Salt Lake, Utah, Atlantic ocean, Pacific Ocean and Fresh
Water - Lake Erie, Lake Huron, Lake Superior,...
Discuss the following questions with
students:
What makes salt water salty? Is it
just salt (ie. NaCl)?
How do you think the salt got there?
What do you think would happen if
you drank salt water every day?
Where does the water that you drink
come from? Is it from an ocean or from somewhere else?
Do the same animals that live in salt
water live in fresh water?
Where do you do fishing? At a lake,
river etc.
Scientific background: Water covers 70%
of the earth's surface. All this water is shown on most world maps
and globes as the same; they don't distinguish between fresh water
and salt water. Of all the water that covers the earth, 97 % of
it is in fact salt water. That means only 3 % is fresh water. Of
this 3 %, two-thirds of it exists in the form of frozen ice. That
leaves only 1 % for human consumption.
Salt Water Facts:
It contains NaCl as well as dissolved
gases and other elements.
It is NOT suitable for drinking or washing
your clothes or hair.
Salt water is found in oceans, rivers
and in saltwater ponds.
About 68% of the earth is covered with
salt water.
Types of animals found in salt water include:
sharks, crabs, whales, octopus, corals, starfish and eels. Salt
water plants include algae and seaweed.
Salt water is made during the process
of erosion - the movement of water on land washes salts and minerals
from the land and carries them to the oceans. Rain on land causes
rivers to not only carry salts found on land to the ocean but
also many other elements, such as gold and silver!
Fresh Water Facts:
It is water with a dissolved salt concentration
of LESS than 1%.
This is the water that you drink, wash
your clothes in etc.
Only about 1% of the earth's surface
is covered with freshwater.
Freshwater can be found in the form of
lakes, ponds, streams and rivers. Ice is also freshwater but frozen,
so the water in the Arctic and Antarctica is salt free.
Assessment/Evaluation:
At this point it is useful to assess students
understanding of the material presented. Students will be given
the following questions listed below to work on in class. The answers
can be taken up together at the end of class or next class depending
on the amount of time left. The teacher may also choose to ask students
to hand in their questions for evaluation.
Resources
Glossary:
bay: a body of water partially surrounded
by land, and inlet of a sea, or other body of water.
canal: a manmade body of water
gulf: a part of an ocean or sea that extends
inland, it is larger than a bay;
lake: a large body of water surrounded
by land.
ocean: a saltwater body that covers nearly
3/4 of the earth's surface.
pond: a smaller body of water surrounded
by land.
river: a body of water of considerable
size that moves and land and usually leads to a bay, gulf, sea,
or another river
stream: a smaller body of water that moves
on land.
Clouds do not have salt in them. Only water
can evaporate.
Yes, large seas and old lakes have salt in
them. Mediterranean Sea and Salt Lake are just a few. Students
need to look at the globe.
Salt comes from the land and water moves over
it and washes it away.
Rivers and streams are moving bodies of freshwater
which usually originate in mountains and come from melting ice
or ground water and eventually terminate in oceans.
If a salt water animal such as a shark were
to go into freshwater, it will take up way too much water, more
than its body is able to hand (due to diffusion). If a freshwater
animal were to go into salt water the opposite will happen - it
will dehydrate. All animals have undergone specific adaptations
suited to the environment in which they are found.
