How Tides Work


Notes
  • This lesson is aimed for 4th-6th grade level students.
  • Students will be using science notebooks. To learn more, go to:http://www.sciencenotebooks.org
  • *This lesson should be taught after students understand the moon's rotation around the earth. Students should be familiar with reflecting and taking notes in science notebooks. During the investigation students should work in groups of 3-5 students.
  • **This activity has been adapted from the "Bulges" lesson in Oceans for Every Kid by Janice VanCleave, published by John Wiley & Sons, Inc.
  • This lesson is also avaible in PDF. Click here to download.
Big Ideas
  • Tides are caused by the gravitational pulls of the moon, sun on the earth, as well as cenfrifugal force on the earth's side opposite of the moon.*
Essentail Questions
  • What are tides and why do they occur?
GLE ties

Science 1.3.7 Interactions in the Solar System and Beyond (universe)
Understand the effects of the regular and predictable motions of planets and moons in te solar system.

Science 2.1.4 Modeling
Analyz how models are used to investigate objects, events, systems, and processes. W

Vocabulary
Tides Gravity Neap tide Centrifugal force (optional) Spring Tide
Possible Misconceptions
  • Tides are caused soley by the earth's rotation (water is sloshing back and forth.)
  • Tides are caused by waves.
  • High and low tides occur at the same times everywhere on earth.
Instructional Strategies
  • Orally describe lesson's "big idea."
  • "Activate Prior Knowledge" Notebooking.
  • "What er know" discussion.
  • Model how to make a model.
  • Students make and explore thier own model.
  • Summarizing discussion.
  • Students journal about new learning.
Assessments
  • Informally check for understanding in each group while they are investigating the models
  • Check for understanding in notebooks.
System Description
  • This lesson focuses on the Ocean Tide System.
  • Important structures:
    • oceans, bays, inlets, rivers
    • the moon, sun, and earth
  • Energy Transfers:
    • The motion of one body of water transfers to another
  • Forces acting on the system:
    • gravity of sun and moon acting upon the water
    • gravity and centrifugal force act upon the water
    • push of current and friction affect the water movement


Lesson Description Materials
  • Per student:
    • Science notebooks
    • pencils
  • Per Group:
    • large zip lock bag
    • floral wiew (to make into an approximately 5-inch diameter circle)
    • large piece of corrugated cardboard (cut from a packaging box)
    • pencil
    • drawing compass
    • scissors
    • marking pen/pencil
    • one 8-inch and one 24-inch piece of string
    • 3 pushpins
    • ruler
    • transparent tape
    • dime
    • quarter
Procedures**
  • Pre-Lesson: Put one of each material (one piece of wire, string, one pencil, ect.) into a large zip lock bag. Make a bag of materials for each group.

    Introduction:

  1. Tell students that today we are going to be exploring what tides are and how they work.
  2. Have students independently notebook on what they know about tides. Some probing questions could be:
    • What is a memorable expirience you've had with tides?
    • What do you know about how tides work?
    • What comes to mind when you hear the words "high tide" or "low tide?"
  3. Ask students to volunteer to share thier writing. While they are sharing, record the main idea of what they said on a white board or piece of butcher paper. Be sure to credit each comment with the name of the student next to it.
  4. Ask students to share thier knowledge of what tides are and how they work, even if they didn't write about it. Include these comments on the board or butcher paper as well.
  5. Investigation:

  6. Make the sun-moon-earth tide model. This will work best if you can use a document camera and projector to show what you're doing. Otherwise, be sure to hold up your work as you go and clearly explain each step. You may want to have students write down the procedures in thier notebooks as you do them.
    • Step 1: Use the cardboard as your base. In the upper center of the cardboard, using a compass, draw a 4-inch diameter circle. Write "Earth" in the middle of it.
    • Step 2: Place one pushpin about 1/2-inch above the drawn circle. Place the other two pins 1/2-inch to the right and left of the ciricle.
    • Step 3: Make the wire onto a circle with an approximatley 5-inch diameter. Place it over the pins (and around the drawn earth.)
    • Step 4: Loosely tie the center of the 8-inch string (so that it can slide) around the wire so that it is opposite of the top pushpin.
    • Step 5: Measure and cut both ends of the string so that the pieces of the string on the wire are 3-inches long.
    • Step 6: Tie the center of the 24-inch string around the wire.
    • Step 7: Measure and cut both ends of the string so that one piece of string on the wire is 3 inches long, and the other piece is 10 inches long.
    • Step 8: Tape one of the originally 8-inch string pieces to the center of the earth circle. Tape a dime on the other side of this string.
    • Step 9: Tape the 3-inch piece of the originally 24-inch string to the center circle. Tape a quarter to the 10-inch side of the string.
    • Step 10: Explain to the students that the dime represents the moon, the quarter represents the sun, and the wire represents the water on earth.
    • Step 11: Slide the dime to the top of the circle (behind the top pushpin), and the quarter to the bottom of the circle (opposite the top pushpin). Pull on each coin with equal force. Ask students what they notice happening to the water. (It should be bulgding alot at the top and bottom of the earth.)
  7. Tell students that they are now going to make thier own model with thier group. When they are done they should experiment pulling the "moon" in different arrangements around the earth and pay attention to what happens to the water. The "sun" should always stay at the same palce, at the bottom of the "earth" opposite the top pushpin.
  8. Hand out a bag of supplies to each student group and have them construct a model like yours. Move around the room to make sure students are on task and know what to do.
  9. After "playing" with the models for a few minutes, have students draw diagrams in thier journals of what the model looks like when the sun and moon are opposite of each other with the earth in the middle (full moon), and when the sun and the moon are aligned on the same side (new moon). Remind students to lable thier diagrams.
  10. Reflections and Sharing:

  11. Ask students to orally share thier observations in a class discussion.
  12. Ask them what conclusions they can draw about tides and thier relationship to the moon and sun from thier observations (highest high and lowest low occure at new moon, there is a little variation between high tide and low tide at the quarter moons).
  13. Explain to the class that a neap tide is when the sun and moon are at 90-degree angles from each other (quarter moons). Neap is a Saxon word that means "scarce or lacking." So, when this occurs there is little variation between a high and low tide.
  14. Then explain that a spring tide is when the sun, earth, and moon are aligned (new and full moon). Th word "spring" is a Saxon word that means "to swell." When this occurs, we have the highest-high tides and the lowest-low tides.
  15. Have students and "neap tide" and "spring tide" to their vocabulary lists.
  16. Optional: You may want to explain that because this centrifugal force causes a bulge opposite of the moon, there are actually two high and low tides a day. However, one is considered the high-high, and one is considered the low-low.
  17. Optional: hvae students are "centrifugal force" to thier vocabulary lists.
  18. Revisit the "what we know about tides" notebooking that was at the begining of the session. After drawing a horizontal line under their original comments, ask kids to write about if something they wrote earlier was erroneous, or they can write about new learning from this activity in thier notebook.
  19. Have students volunteers share thier reflections.

    *This Lesson should be taught after students understand the moon's rotation around the earth. Students should be familiar with reflecting and taking notes in science notebooks. During the investigation students should work in groups of 3-5.

    **This activity has been adapted from the "Bulges" Lesson in Oceans for Every Kid by Janice VanCleave, Published by John Wiley and Sons, Inc.

Assesement
  • Either working independently or in groups, ask students to explain in their notebooks the sun and moon's placement when the most extreme high and low tides occur (at the new moon). Also, have them draw a labeled diagram to show this understanding.