|
Going
Further
Water
Currents
Purpose
To demonstrate that ocean currents are
influenced by changes in water density
To observe how temperature and salinity affect water
density
Materials
- food coloring
- ice cube tray
- fish bowl, small aquarium or any glass bowl of
similar size
- salt
- test tube or small cup
- hot tap water (43°C or 110°F)
- thermometer
Background
Information
Ocean water is salty and, in general, cold. Most ocean
water is less than 36°F (2.2°C). But in the
tropics, surface water may reach 82°F (28°C), and
water can be much hotter near underwater volcanoes.
Differences in water density associated with temperature and
salinity play an important role in in shaping ocean
currents.
Procedure
- Set up
- Several hours before you need to begin he experiment,
add 5-7 drops of food coloring to a small amount of
water. Pour the colored water into an ice cube tray to
make 1 colored ice cube. Make sure the color is very
dark.
-
- Temperature (Part 1)
- 1. Fill a fish bowl, aquarium, or other glass
container to the rim with room temperature water. Let it
stand for about a minute so that the water will have a
chance to settle before you start.
2. Place the colored ice cube into the water very
gently and observe for 1 minute or more. Record your
observations. Do not disturb the tank until after the ice
cube has completely melted. Observe again and record your
observations.
3. Describe your findings and explain why this
happened.
-
- Temperature (Part 2)
- 1. Empty the fish bowl or glass container and then
refill it with fresh water at room temperature.
2. Run hot water until the temperature is at least
110°F (43°C). Fill a test tube or small cup
half full with this water. Add 5-7 drops of food coloring
until the color is very dark. Very gently pour this
colored hot water into the tank. Observe for a minute or
more. Record your observations.
3. Describe your findings and explain why this
happened.
-
- Salinity
- 1. Empty the fish bowl or glass container and then
refill it with fresh water at room temperature.
2. Fill the test tube or cup half full of colored salt
water; use 5-7 drops of food coloring to give it a dark
color and 1/2 teaspoon of salt.
Very gently pour the colored salt water into the tank and
observe. Record your observations.
3. Describe your findings and explain why this
happened.
Going
Further
Where in nature might you find conditions similar to
those in the three different demonstrations? How do they
interact with one another?
|
