Lesson for Stanford's Science Bus (1 Hour with Grades 2-5)
Ocean Currents
Lesson for Stanford's Science Bus (1 hour with grades 2-5)
Head Tutor: Alex Sugarbaker
This lesson consists of 3 demos with a large fish tank at the front of the class and 3 short hands-on activities for small groups. One or two of the tutors should be able to refill the tank while the other tutors do the activities in groups of 4-6 students.
Outline
1. Worksheeton ocean currents (10 min)
2. Demo hot and cold water mixing in the fish tank (5 min)
3. Small groupsexplore wind and ocean currents (10 min)
4. Demo salt water in the fish tank (5 min)
5. Small groupsexplore "thermohaline" effects (10 min)
6. Demo sunlight and ice caps in the tank (5 min)
7. Small groupscheck bottled ecosystems from last week (5-10 min)
1. Worksheeton ocean currents (10 min)
See the last page. Discuss "thermohaline" effects (salt water and cold water sink, fresh water and hot water rise) and the importance of wind and landmasses. Look at the ocean currents map. Describe the importance of currents for life in terms of recycling minerals and nutrients and transporting heat (Gulf Stream and Europe).
2. Demo hot and cold water mixing in the fish tank (5 min)
Fish tank
Glass jars with lids (and or burettes)
Red and blue food coloring
Ice cubes
Hot plate
Fill the tank with room temperature water and watch the hot and cold water rise and fall.
3. Small groupsexplore wind and ocean currents (10 min)
(copied from Teacher Vision,
Tin pie plates
Thyme (floats)
Mustard seeds (sink)
Plastic straws
1. Point out that ocean currents are driven by the wind and influenced by the landmasses that obstruct the flow of water as well as the density and temperature of the water.
2. Fill a tin pie plate to the inner rim with cold tap water.
3. Sprinkle thyme on the surface and mustard seed on the bottom
4. Using a plastic straw, gently blow across the surface of the water
5. Repeat with less water if time remains
Students should observe that the water is rippled by the artificial wind they create and that the currents on thesurface circulate around the edges of the pan. Point out that the wind they created is analogous to the EquatorialCurrents flowing west at the Earth's equator. These currents are forced into a clockwise rotation in the NorthernHemisphere and a counterclockwise rotation in the Southern Hemisphere because of the Earth's rotation and thelandmasses that obstruct the waters' flow. They should also observe the distinction between surface and deep sea currents, since the mustard seeds are unaffected by their wind.
4. Demo salt water in the fish tank (5 min)
Fish tank
Glass jar with lid
Salt (lots of it)
Green and yellow food coloring
Mix the salt, food coloring, and water in the jar, then watch it plummet in fresh water. A fresh water control jar couldn't hurt.
5. Small groupsexplore "thermohaline" effects (10 min)
(copied from Bill Nye's home demo Planetary Science: Earth Science: Current Event,
Glass bread loaf dish
30 milliliters of salt (2 tablespoons)
Blue food coloring
Ice cubes
1. Mix 30 milliliters (2 tablespoons) of salt and a liter (quart) of water in a glass dish.
2. Put it in the freezer until it's cold, so chips of ice form on the surface (~30 min).
3. Remove the dish from the freezer, and carefully drip a few drops of blue food
coloring onto the surface.
4. What happens as it melts?
5. Place an ice cube at one end of the dish. What happens?
The freezing chemically squeezes the salt out of the water. The dark blue layer
of food coloring is not salty, so it won't sink! When the ice melts, it's fresh water
- no salt. The salty water is heavier (denser) than the fresh water so the fresh
water floats on top of it. When you add an ice cube, the cube is colder than the
surrounding water and it will cause the water to become denser than the seawater.
The dense water will sink pulling some of the blue color with it. When icebergs
melt, they usually cool the sea below them, but their freshwater stays on the
surface for a long time. Many ocean currents are driven by the flow of heat and
salt in the ocean. We call these "thermohaline" (therm-oh-HAY-leen) currents.
That means heat and salt currents. They're cool. Well, they're cold. They're caused by the flow of heat.
6. Demo sunlight and ice caps in the tank (5 min)
Fish tank
Bright lamp
Large block of ice
Blue food coloring
Set this up as quickly as possible after the previous demo so it reaches thermal equilibrium during the "thermohaline" activity. Shine the light on one half of the tank and put the ice block in the other. Make an analogy to the ice caps and equator. Drop in some food coloring near the ice block and observe the currents. If that isn't visible, can you see the rotation with other floating debris?
7. Small groupscheck bottled ecosystems from last week (5-10 min)
Which ones made it? Do you need a plant, a worm, soil, and water for the ecosystem to thrive? What about salt and sand?
For more information, watch:
(Bill Nye, demo ideas from Bill Nye)
(NOAA)
And of course, all of the demos and activities need lots of water!
Worksheet to appear here in final draft.