Convection Currents

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Convection Currents

  1. 1. Convection 4-2
  2. 2. Uneven Heating Questions <ul><li>What causes Earth’s surface to heat up? </li></ul><ul><li>What are some of the variables that cause uneven heating of Earth’s surface? </li></ul><ul><li>What happens to the temperature of equal volumes of soil and water when they are place in the sunshine for 30 minutes? </li></ul>
  3. 3. Density <ul><li>What will happen to these objects when I drop them into the water? </li></ul><ul><li>Object Results </li></ul><ul><ul><li>Floats - less dense than water </li></ul></ul><ul><ul><li>Sinks - denser than water </li></ul></ul><ul><li>Which objects are less dense than water? </li></ul><ul><li>Which objects are denser than water? </li></ul><ul><li>Is water denser or less dense than cork? </li></ul><ul><li>Is a vial cap denser or less dense than a penny? </li></ul>
  4. 4. Cold Water Challenge <ul><li>Do you think the blue ice water is denser, less dense, or the same density as room-temperature water? </li></ul>
  5. 5. Challenge Procedure <ul><li>Fill vial with room temperature water. Let stand 1 minute undisturbed. </li></ul><ul><li>Use bulb pipette to take up bulbful of blue cold water. </li></ul><ul><li>Gently squeeze bulb to release blue cold water on either the bottom or the surface of the vial of water. Use a steady slow squeeze. </li></ul><ul><li>Observe the vial carefully to determine if the cold water floats or sinks. </li></ul>
  6. 6. Observations <ul><li>What happened to the cold blue water when it was placed in room-temperature water? </li></ul><ul><li>Why do you think the blue water went down? </li></ul><ul><li>Is the blue ice water denser, less dense, or the same density as room-temperature water? </li></ul><ul><li>What do you think will happen if you warm up the bottom of the vial where the cold water is sitting? </li></ul>
  7. 7. Hot Water Investigation <ul><li>Carefully place the vial with blue water on the bottom into a plastic cup. </li></ul><ul><li>Fill zip bag half full of hot water, using the syringe. Seal top of bag shut. </li></ul><ul><li>Slowly lower bag of hot water into the cup with the vial. </li></ul><ul><li>Closely observe the blue water carefully for 4 minutes. </li></ul><ul><li>Make accurate illustrations of movement of cold blue water. Write captions under each illustration. </li></ul>
  8. 8. Hot-Water Results <ul><li>What happened to the cold blue water in the vials after the hot water was placed beside it? </li></ul><ul><li>Why do you think the blue water moved up? </li></ul><ul><li>Why do you think warm water moves up? </li></ul><ul><li>Why do you think the blue water started to sink after coming to the surface? </li></ul><ul><li>What pattern did the blue water make after the hot water was added? </li></ul>
  9. 9. Vocabulary <ul><li>Materials sink in water if they are denser than water. </li></ul><ul><li>Materials float in water if they are less dense than water. </li></ul><ul><li>Convection Current </li></ul><ul><ul><li>A circular current in a fluid caused by uneven heating </li></ul></ul>
  10. 10. Content <ul><li>Is hot water denser or less dense than room-temperature water? </li></ul><ul><ul><li>Hot water is less dense than room-temperature water. </li></ul></ul><ul><li>Which is denser, hot water or cold water? </li></ul><ul><ul><li>Cold water is denser than hot water. </li></ul></ul><ul><li>What causes a convection current? </li></ul><ul><ul><li>Occurs when the bottom of a mass of fluid is heated. Warm water rises, cools, and then descends, creating a circular flow. </li></ul></ul><ul><li>Your questions? </li></ul><ul><li>Homework: Read Wind! Pg. 202-207 and answer questions. </li></ul>
  11. 11. Wind! Questions <ul><li>Explain how convection currents are produced in the air. </li></ul><ul><li>Explain what causes wind. </li></ul><ul><li>Describe what happens to air molecules when air is heated. </li></ul><ul><li>What is the source of energy that causes the wind to blow? </li></ul>

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