To the teacher: This CPO Science PowerPoint presentation is designed to guide you through the process of presenting the lesson to your students. The presentation uses a 5-E teaching model: Engage, Explore, Explain, Elaborate, and Evaluate. The PowerPoint Slide notes indicate where you may want to bring in various lesson elements such as quizzes, readings, investigations, animations, and practice materials. Additional science background information is provided in the slide notes where appropriate. You can view these notes by selecting “View,” then “Normal.” You will see the notes pane at the bottom of the PowerPoint workspace. Additionally, the slide notes are available as a separate document, accessible from the lesson home page. The slides that follow are intended for classroom use. About the slide notes: The slide notes for this presentation are available in a separate document that you can print and look at while you use the slides. You can access the slide notes document from your teacher lesson home page. Enjoy the lesson!

Energy from the Sun What does this graphic have to do with wind and ocean currents? What heat transfer process is involved in creating wind and ocean currents? Sketch how this heat transfer process works. Use the word density in your answer. ENGAGE: Earth’s primary source of energy is the Sun. This graphic shows that this energy is absorbed by the atmosphere and Earth’s surface (both land and water). Because plants depend on the Sun to photosynthesize, life could not exist without the Sun’s energy. Aspects of our environment like wind and ocean currents are also dependent on this energy. Convection is the heat transfer process involved in creating wind and ocean currents. Sketches should show an energy source (like the Sun) warming a fluid (air or water). Warmer fluid should be labeled as less dense so that it rises. Cooled fluid should be labeled as more dense so it sinks. This rising and sinking creates a convection current that can happen in air (creating wind) or water (contributing to ocean currents). If you have time, try this demonstration to help students see that a volume of air molecules expands (becomes less dense). Place a balloon over the top of a flask. Chill the flask in ice water, then immediately place the flask into a bucket of warm water. This change in temperature will cause the air inside the flask to warm, become less dense, expand, and rise. This causes the balloon to inflate. Then place the flask with inflated balloon back into the bucket of cold water. What happens? The balloon deflates as the air becomes cooler, denser, and sinks.

Time to investigate! Complete the lesson investigation: Convection in Earth’s Atmosphere Hawks use convection to soar. They are lifted higher in the sky by rising currents of warm air. EXPLORE: Lead the lesson investigation: Convection in Earth’s Atmosphere

What causes wind? The Sun’s energy and convection cause wind. Unequal heating of the atmosphere by the Sun creates pressure differences. Rising, warm air in a convection cell creates a low pressure. Sinking, cool air creates high pressure. Air moves horizontally from high to low pressure areas. This horizontally moving air is called wind. EXPLAIN: Land heated by the Sun warms the air above it. This air becomes less dense and rises, creating a low pressure area. Air that is cooled is denser and sinks , creating a high pressure area. This is what causes a horizontal movement of air (wind) from a high to low pressure area. The greater the pressure difference, the faster the wind.

What causes ocean currents? Surface ocean currents: Permanent global wind patterns push water and create these currents . Example: The Gulf Stream. Deep ocean currents: These currents are driven by density differences created as the Sun’s heat and wind increase evaporation at the equator. EXPLAIN: The Sun’s unequal heating of Earth and the Coriolis effect cause permanent global wind patterns (i.e., the trade winds, prevailing westerlies, and the polar easterlies). Global wind patterns and heat speed up evaporation of water near the equator. When ocean water evaporates, the water leaves and the salt stays behind. When this happens, surface ocean currents near the equator become saltier. A surface ocean current cools as it moves from the equator toward the poles. Because this water is saltier than surrounding water and because it is now cooler, it sinks to the ocean floor as a huge underwater waterfall. What was once a warm surface ocean current now flows along the ocean floor as a cold deep ocean current. Eventually, the slow-moving deep ocean current water returns to the surface in a upward-moving upwelling. Upwellings return the original surface water and nutrients from the ocean bottom back to the ocean surface. This huge convection cycle takes hundreds to thousands of years.

Time for Practice! Complete the lesson practice activity: Convection in Earth’s Atmosphere ELABORATE: Convection near coastlines causes sea breezes during the day and land breezes at night. These breezes occur because water has a higher specific heat than land. This means that water, heated by the Sun’s energy, warms and cools more slowly than the land. During the day the high pressure region is over water and so a sea breeze occurs. At night, the more quickly cooling land is the high pressure area, so a land breeze occurs.

Show what you know! Try the lesson’s interactive quiz, or complete a quiz that your teacher can print out for you. Hint: You might want to review your lesson reading piece one more time before trying the quiz. EVALUATE: Print out the 10-question quiz for students to complete, or have students work individually at computers to complete the interactive quiz they can access from the multimedia lesson home page.