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Activity

Water cycle model

Summary: 
A closed container with warm water and a small pot to collect the evaporated, then re-condensed, water shows how freshwater lakes are made from salty ocean water.
Science content (2016 curriculum): 
Earth/Space: Water cycle, Water conservation (2)
Science topic (2005 curriculum connection): 
Earth and Space Science: Air, Water and Soil (grade 2)
Earth and Space Science: Weather (grade 4)
Physical Science: Properties of Matter (grade 2)
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Lessons activity is in: 
Materials: 

For each model (can use one per table group)
• sturdy plastic storage tub, roughly 30cm long x 15cm wide x 15cm tall
• small heavy pot, not much more than half the height of the tub
• 3 tablespoons salt
• 5 drips food colouring
• cling film to cover the top of the tub with at least 5cm overlap
• masking tape
• 4 small binder clips
• kettle and water
• a marble
• Q-tips, one per student

Procedure: 

Prepare the activity:
Lay a piece of cling wrap over the top of the plastic tub. Use masking tape to secure the cling wrap most of the way round, leaving it open the last 1/4 of the length. Add the salt and food colouring at one end of the plastic tub (make separate piles). Place the pot in the middle of the tub.
In class:
Boil the water, then immediately add it on top of the salt to a depth below the rim of the pot (it will not work unless the water is only just boiled). Clip the lid shut by securing the cling wrap with binder clips. The cling wrap may balloon up. Place the marble in the middle of the cling wrap, directly over the pot.
After 5 mins or so, drips of re-condensed water will fall from under the marble into the pot. After 10 or 15 minutes there will be enough drips of water in the pot to have made a puddle.
The students can taste the water in the pot ("the lake") and the tray ("ocean"). The ocean water is salty and the lake water is fresh. Only the water evaporates from the ocean - the salt is left behind. The food colouring also stays in the ocean, but does not appear in the lake.

Grades tested: 
Gr 1
Gr 2
Gr 3
Teacher: 
Anke Barabulea
Candace Wong
Ingrid
Linda Bierbrier
Miriam Sanz
Teaching site: 
General Gordon Elementary
McBride Elementary
ProD for Elementary teachers
West Coast Christian School