Day 4: tides
Objectives:
- The students will be able to explain the effect of the moon's gravitational pull on the waters of the Earth (the tides)
- The students will be able to examine a simple tide chart to determine the high and low tides of the day.
- The students will be able to explain the effect of the moon's gravitational pull on the waters of the Earth (the tides)
- The students will be able to examine a simple tide chart to determine the high and low tides of the day.
Materials: Tide Table, with a few days cut out/highlighted, rubber bands, globe, ball for moon, pennies or other circular objects.
Procedure:
- Read Catching the Moon, by Myla Goldberg.
- Write "gravity" on the board. Ask children if they know what gravity is, or what it does. Explain that gravity is a pulling force. The Earth pulls us down towards it, which is why we don't float away. The sun pulls the Earth towards it, which is why we orbit. In the same way, the moon pulls on the oceans.
- Ask students what they think happens when the moon's gravity pulls on the oceans. After a few answers, if no one has suggested tides, ask them "Have you ever been to the beach, and noticed that the water is really far away sometimes, and sometimes it comes way up high on the sand?" or something similar. Explain that that is high tide and low tide.
- Remind students that it takes almost a month for the moon to revolve around the Earth. But, it only takes 24 hours for the earth to rotate. Demonstrate what that looks like, with the globe and ball (moon).
- Explain that if the moon's gravity is pulling on the water, that means that the water closest to the moon is going to raise, and be high tide. Ask them then how many times there must be high tide in one day. They will probably say "one!", but the answer is two. You can show them this video: http://www.youtube.com/user/minutephysics/videos. It moves very quickly, so after you watch it, explain in more detail. Also explain that the rotation of the Earth causes another bulge on the opposite end, away from the moon, which also feeds the high tide.
- Hand rubber bands out to the students. Have the students put the rubber bands on their desks, formed into a circular shape.
- Have students place the penny/circular object outside of the rubber band. Explain that that is the moon, and the rubber band is the water on Earth. As the moon rotates around the Earth, (the penny circles the rubber band), have the students create a little bulge on that spot. Point out the second "high tide" that will form on the opposite side. Collect rubber bands/objects.
- Hand out modified tide table. Have students paste them into the right side of their interactive notebooks. Explain how to read the chart, Ask them how many big numbers they see, and how many small numbers. Explain that those numbers are the highest and the lowest the water gets. Elicit responses from the students about various days' high and low tides.
- Have students record high and low tides for three days on the left side of their notebooks. This will serve as the summative assessment.
Differentiation:
A highly simplified tide table can be used, or not used at all.
Neap and spring tides can be introduced, as well as the interaction of the sun in tides.
A highly simplified tide table can be used, or not used at all.
Neap and spring tides can be introduced, as well as the interaction of the sun in tides.
Assessment:
Formative: Ask students for details of what is happening as they do the rubber band exercise.
Summative: Interactive Notebooks
Formative: Ask students for details of what is happening as they do the rubber band exercise.
Summative: Interactive Notebooks
Resources: None