Lesson Title: What Causes Tides?

Standards: Science (Newton's Third Law of Motion, Constructing Models)

Math (Measurement, Reasoning)

Learning Style: Visual-Spatial Logical-Mathematical, Intrapersonal, Interpersonal, Verbal-Linguistic

Goal: Explain how the sun and moon affect the tides.

Grade Level: 4th Grade

Time: 35 minutes

Background Information:

What are ocean tides? Ocean tides are the alternate rising and falling of the surface of the ocean that usually occurs in two intervals everyday, between the hours of 7a.m. to 7p.m. It is caused by the gravitational attraction of the sun and moon occurring unequally on different parts of the earth. The moon is the main cause of the tides because it has a stronger gravitational pull, and it is closer to the earth than the sun. The gravitational pull is more visible with the ocean than the land because the ocean consists of liquid, which is more flexible then solid land. When the moon faces the earth, it exerts a stronger attraction than the side that is facing away, causing the water to be drawn towards the moon. This rise of the sea is known as high tides, which usually occur around 7a.m. to 2p.m. When the moon moves away from that point it causes the water to fall, creating low tides from 2p.m. to 7p.m. (Newton's Third Law of Motion: "For every action, there is an equal and opposite reaction") Since the earth is not drawn towards the moon as much as water is, it causes the earth on the opposite side of the world to be pulled away from the water. At the same time it is also creating another high tide that is not as stronger as the one facing the moon, on the opposite end of the world. High tide and low tide occur twice every 24 hours and 50 minutes. This is the time it takes the moon to complete one orbit around the world.

Source: http://www.oxy.edu/~cimac/student97/helen.htm (3/1/99)

Prerequisite Information:

Definitions of high and low tides, gravity, and Newton's Third Law

1. Exploration Phase (Tide in a Bottle)
   1. Objectives: Within groups, students will observe tides, and make a hypothesis about their observation. The teacher will assess their understanding by having students share their results with the class, and discuss them. The hypotheses should reflect that high tide in one location equals low tide in another.
      
   2. Materials: 4- 2-liter plastic bottles

      1 liter of water for each bottle

      1 liter of vegetable oil for each bottle

      Blue food coloring

       

   3. Introduction of Lesson: Inform students that they are going to be oceanographers today and their job is to explore tides. Ask students of any prior experiences with tides and the ocean.
      
   4. Procedure:
      • Students share accounts of beach visits or opportunities they may have had to view waves collapsing sandcastles or crashing onto the shoreline.
      • The teacher introduces the class to the concept of waves and tides and defines the terms. (Wave = the movement of the energy in water, but the water itself is not moving. Tide = the alternate rising and falling of the surface of the ocean that usually occurs in two intervals everyday.)
      • Discuss and explain Newton's Third Law of Motion.
      • The teacher displays a pre-made "Tide in a Bottle" and demonstrates the concept of low and high tides by holding one end of the bottle in each hand and tilting the bottle from side to side.
      • The students observe that when the water level rises at one end of the bottle, creating a high tide, it is lowered at the opposite end of the bottle, creating a low tide. Waves are also formed during the tilting process.
      • The students are divided into three groups.
      • Each group is given a "Tide in a Bottle" and the following directions:

        -You are now ready to experiment. Swirl the bottle while it's standing up or lay it down on its side and rock back and forth to create "waves".

        -You will find many interesting things to do with it. Try creating large bubbles by turning the bottle top over bottom a few times.

        -Really shake it up to create millions of tiny bubbles.

        -Look into the depths of the bottle when it has so many tiny bubbles with an "unfocused" gaze to get a holographic type effect. It also really looks great when lit from behind. Hold it up to the window on a sunny day to get an even more colorful effect.

        -Each student then is given the opportunity to create high and low tides, and to create waves.

      • A class discussion of the correlating cause-and-effect follows.

Source: http://www.coreknowledge.org/CKproto2/resrcs/lessons/1getyourfeetwet.htm (3/1/99)

http://www.funroom.com/summer/wavemkr.html (3/1/99)

1. Evaluation: Each group must submit a brief explanation orally as to what happened when they observed the tides. The explanation should include a basic understanding of Newton's Third Law of Motion, but does not need to be quoted exactly.
1. Invõntion Phase (Rocket & Newton's Third Law of Motion)
2. a. Objectives: Students will demonstrate Newton's Third Law of Motion by constructing a model rocket in groups and theorize what caused the rocket (lid) to fly. Likewise, students will measure the distance the model rocket travels in their groups. After completion of the project, each student will complete a worksheet pertaining to Newton's Third Law of Motion, where they answer at least the last question correctly.
3. b. Materials: Construction paper

   4- 35 mm film canisters

   Alka-Seltzer tablets

   Tape

   Paper towels

   Hot glue gun

   Yardsticks

   Water

   Worksheet

   1. Procedure:
   • The students are divided into three groups.
   • Explain that each group will be making one model rocket, with each student contributing to the project.
   • Wrap paper around the film canister to form a cylinder. The paper should simply fit the canister without any leftover paper. Be sure that the open end of the canister is down!
   • Cut four fins (squares or rectangles) and tape onto your rocket.
   • Use the pattern to cut a nose cone and glue onto your rocket. (This has been previously prepared for students)
   • Turn the rocket upside down and fill the canister 1/3 full of water.
   • When finished with preparation, as a group, bring model rocket to teacher.
   • Teacher will launch the rockets for students in the hallway, and handle the Alka-Seltzer tablets.
   • VERY QUICKLY: The teacher drops in 1/2 Alka-Seltzer tablet, snap on the lid, and stand rocket on launch platform. Stand back!
   • Using a yardstick, students will measure how far the rocket (lid) traveled.
   • Students return to the classroom to hypothesize what caused the rocket (lid) to fly.
   • Each group shares their hypotheses of why the rocket flew, and as a class determine which group's rocket went the furthest.
     
   1. Evaluation: After discussion, students will individually complete a worksheet pertaining to the experiment to demonstrate their understanding of Newton's Third Law of Motion.

Source: http://www.glenbrook.k12.il.us/gbssci/phys/class/newtlaws/u214b.html (3/1/99)

1. Expansion Phase (Sun, Moon, Tides)
   
   1. Objectives: As a class, students will hypothesize how the sun and moon affect the tides. After the class discussion, students will individually write a paragraph in their journals about how the sun and moon affect the tides. Each student's paragraph should reflect an understanding of tides and include Newton's Third Law of Motion in their explanation.

       

   2. Materials: Science Journals

      Transparencies of Tides

      Overhead Projector

       

   3. Procedure:
   • Ask the class how they think the sun and moon affect tides.
   • Write their ideas on the overhead projector. (Have class think about experiments they have performed thus far.)
   • Expand on students' ideas and explain how the sun and moon affect tides.
   • Have students individually write one paragraph in their journals how the sun and moon affect tides. (Should include Newton's Third Law of Motion, and class discussion.)
   • Have students turn in journals.
     
   1. Evaluation: Read students' explanation in their journals about how the sun and moon affect the tides, and check for understanding. The students' explanation should include facts from the class discussion, and incorporate Newton's Third Law of Motion.