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Water

Water. Investigation 1 Part 2: Surface Tension. Essential Question. What factors influence the shape of water?. What You Will Learn. The shape of water on a flat surface. Water has a property that affects its shape.

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Water

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  1. Water Investigation 1 Part 2: Surface Tension

  2. Essential Question • What factors influence the shape of water?

  3. What You Will Learn • The shape of water on a flat surface. • Water has a property that affects its shape. • This property of water can be affected by the addition of other substances.

  4. Question How many drops of water do you think you can fit on a penny? Raise your hand and we’ll record your guesses.

  5. Task You will work in pairs to place drops of water on a penny following the procedure I’m demonstrating. • Place a dry penny on a paper towel. • Use a dropper to placed drops on the penny one at a time. • Hold the dropper straight up and down and release drops from about 1 cm above the penny. • Count the number of drops as you go until the water spills.

  6. Directions • The getters will get a tray with enough materials for each pair of students when I say “materials.” • Working in pairs take turns dropping drops on the pennies. Record the number of drops on the penny each time before the water falls off the penny. • Dry off the pennies between each trial.

  7. Discuss the Results • What was the most drops you could drop on the penny before the water ran off? • Record these amounts next to the estimates. • What shape was the surface of the water on the penny before it spilled?

  8. Discuss Results • This is a side view of the penny and the water.

  9. Vocabulary • Surface Tension – the skinlike surface on water (and other liquids) that pulls it together into the smallest possible area (sphere) • Dome – the shape a drop of water takes when it is on a flat surface. It is like a flattened hemisphere.

  10. Surface Tension • The curved surface of the water shows us an interesting property of water. Scientists call this property surface tension. • Surface Tension causes water to stick together and try to form into a ball.

  11. Question • What will happen if soapy water is added to a water dome on a penny? • Discuss this with your partner. • Share.

  12. Task • Set up as before with a dry penny on a paper towel. • Put 15 drops of plain water on a penny to make a dome. • While observing the domefrom the side, add one drop of soapy water to the dome. • Count the number of additional drops of soapy water needed to spill the dome.

  13. Directions • When I say “materials,” the getters will get a cup of soapy water, a new dropper, and a clean dry penny. • Make sure that the new dropper is used only in the soapy water. Do not put this dropper in the plain water. • Do not put the dropper you use in the plain water in the soapy water.

  14. Directions Cont’d • Materials. • You may begin. • Be sure to record the number of drops.

  15. Discuss Results • Reporters, what happened to the water dome on the penny when soapy water was added? • Does soap affect surface tension? How do you know? • Discuss in your groups. • Share.

  16. Directions • We will do the same task as before, but this time we will use salt water. • When I say “materials,” the getters will get a cup of salt water, a new dropper, and a clean dry penny. • Make sure that the new dropper is used only in the salt water. Do not put this dropper in the plain water.

  17. Discuss Results • Reporters, what happened to the water dome on the penny when salt water was added? • Does salt affect surface tension? How do you know? • Discuss in your groups. • Share.

  18. CONTENT/INQUIRY • What shape does water make on a flat surface? • Water forms a dome on a flat surface. • Why does water form a dome on a flat surface? • Surface tension makes water form a sphere or dome. • How did you change the surface tension of plain water? • Soap added to water reduces its surface tension. The dome flattens when soap is added to water.

  19. Clean Up • All students must neatly put their materials on the tray. • The collectors will take the materials back to the science table.

  20. Vocabulary Review • Surface Tension – the like surface on water (and other liquids) that pulls it together into the smallest possible area (sphere) • Dome – the shape a drop of water takes when it is on a flat surface. It is like a flattened hemisphere.

  21. What You Learned Today • Water forms a dome on a flat surface. • Surface tension makes water form a sphere or dome. • Soap added to water reduces its surface tension. The dome flattens when soap is added to water.

  22. Record Observations • Record your observations during these tasks on the Surface Tension Record sheet.

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