Circling Around! (Evelyn Ozuna)

Title: Water Density

Principle(s) Investigated: Students should be able to conclude that the temparature of a substance affects its density.

Standards : 4.a. Students know uneven heating of Earth causes air movements.

6.g. Record data by using appropriate graphic representations and make inferences based on those data.

6.h. Draw conclusions from scientific evidence and indicate whether further information is needed to support a specific conclusion.

Data Table

Materials:

• goggles
• large, clear plastic container
• 2 test tubes
• water
• ice
• food coloring, red and blue

Procedure:

1. Students will work in groups. The first go getter of the group members will half-fill the large plastic container with water at room temperature. Second go getter will half-fill one vial with hot water. (Died in red food coloring)
2. One group member will place the valve inside the container and lower it to the bottom of the container.
3. Group members must predict what will happen to the colored water when top is removed from the vial. Group members will record their predictions on their science journal.
4. Student will remove the top from the vial and observe what happens to the colored water. Students will record their observations.
5. A new group member will repeat the experiment. This time using ice water containing blue coloring.

Student prior knowledge:

Students need to understand the concept of wind. Wind is air in motion. It is produced by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of various land and water formations, it absorbs the sun’s radiation unevenly. Two factors are necessary to specify wind: speed and direction. They also have to understand what is density and convection.

Explanation: When you're dealing with fluids, you have to account for density and buoyancy as well. Air is the fluid we live in. When we heat air, the molecules jiggle and zip around faster, which causes them to spread out. When a mass of air takes up more space, it has a lower density. When you have a lower density fluid immersed in a higher density fluid, the lower density fluid rises and the higher density fluid falls. Warm air rises when it's surrounded by cold air because of its lower density. Heat can move up, down, or sideways, depending on the situation. What the laws of thermodynamics tell us is that heat moves from areas of higher temperature to areas of lower temperature.

Questions & Answers:

1. What is a convection current?

Answer: A convection current is any movement of matter that results from differences in density, may be verticle, circular, or cyclical.

2. How do convection currents distribute heat in the ocean?

Answer: Convection currents transfer energy as they flow. Warm water at the surface absorbs energy from the sun and carries this energy to colder regions. The warm water cools due to its cooler surroundings. As the water cools, it becomes denser and sinks. Then the deep water rises to the surface as surface water moves away. The cold water warms and the cycle continues.

3. How do ocean currents affect climates?

Answer: Surface currents affect the climate in many parts of the world. The surface temperature of the water affects the temperature of the air above it. Warm currents heat the air and causes warmer air temperatures.

Applications to Everyday Life:In the earth's deep mantle and outer core, the magma that is closer to the exteremely hot inner core rises because it's less dense and then pushes the cooler magma that is further from the intense heat down. When the cooler magma is pushed down, it is heated more and rises. The somewhat less hot magma is more dense and so sinks. This motion is convection currents and is what causes the plates to move that are riding on the surface of all of this.

Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.

Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made. http://www.youtube.com/watch?v=bVZ_7-MA4D4&feature=related