Water Cycle - Oceans (K)
Pre Lab 

   
OBJECTIVES:
  • Demonstrating the contents of water.
  • Analyzing the contents of clear water.
VOCABULARY:
  • evaporation
  • fresh water
  • lake
  • ocean
  • salt water
MATERIALS:

Students predict whether liquids are salty or fresh.

BACKGROUND:

The majority of the Earth’s water can be found in oceans.  The water however is not pure.  It has other components, for example compounds, elements, or small particular matter, that have been dissolved in the water over eons of time, as water eroded the Earth’s surface.  Young children do not realize that water fills the low spots on the Earth’s surface.  Islands are not floating in water, but high mountains surrounded by very low valleys. 

Salt water is not good for humans.  The salt in the water makes the liquid undrinkable to humans because our body cannot take out the salt.  Too much salt in our bodies is not good for it. Salt and fresh water and very different. 

The term salt water is misleading because it contains more than just table salt (sodium plus chlorine).  It also has other compounds, including sodium plus iodine and bromine.   The term seawater is also used to refer the ocean’s water. 

PROCEDURE:
  1. Explain the differences between fresh and salty water.  Some students may misunderstand the word "fresh" and think it is naughty water.  You may want to show students on a globe or map that oceans are salty and lakes are fresh.  Slowly say the oceans, Atlantic, Pacific, Arctic, and Indian are salt water.  Point out the Great Lakes in the United States as fresh water.  If you have local bodies of fresh water, discuss them.  
      
  2. It is very difficult for students to "see" what is in water.  In this demonstration the students will learn that clear water may have something in it.  Start off this pre lab by discussing and describing water.  Ask the students how they can tell if they have salt water or fresh water.
      
  3. Mix salt and water, epsom salt and water, and plain water.  Make sure that all the salt and epsom salt is dissolved by using warm water.  Mix the ingredients before showing the children.  Have students predict which sample is clean, and which samples with nothing visibly in it.   Record their answers on the board. 
      
  4. Put some dishes out in a place where the water can evaporate.  Have students look at the dishes every day, asking students the same questions.   If you have a hot plate or if it is a warm day, you should be able to do this quickly.  Make sure you make a thin layer of liquid in the dishes.  Go back to their predictions to see if they guessed right.

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