It is important for students to know how much of our earth is made up of water, but the concept is very abstract and often difficult for younger students to understand. With this simple and fun activity, the difficult concept is brought to a level that even very young people can grasp.
Now that you realize how much land and water are on earth, does that change any ideas you had?
How could the amount of water on earth affect a growing population?
Can you make a prediction about the land animal and water animal populations on our earth?
Students will gain the knowledge and understanding that the surface of the earth consists of more water than land.
Students will gain an understanding of the concept of probability, using percentages.
An inflatable globe
Can be purchased at most toy stores
NASA Earth Science Site
This web site for the National Aerospace Administration has beautiful pictures of Earth, taken from space. It is also a good source of Earth Science activities for teachers.
Divide into pairs. If not enough balls are available or there are time constraints, larger groups may be used.
Examine the inflatable globe. Each of you should make a prediction of how many times you think your right index finger will end up on land, and how many times it will fall on water.
No matter the size of the group, the ball should be tossed a total of 100 times. It is important that an accurate count be kept. A tally must be kept of how many times the catcher's right index finger is touching water, and how often it is touching land. Once again, IT IS VERY IMPORTANT THAT AN ACCURATE COUNT BE KEPT. A good option is to assign one person per group to be the tally keeper, and not have that person catch and throw.
After the ball is thrown a total of 100 times, it is time to find the percentage of times the finger was on water, and the percentage it was on land. To do so, you will divide the number of times the finger was on land by 100, and move the decimal to the right two places. This is the perentage of land. Then, the number of times the finger was on water is divided by 100, and the decimal is moved 2 places to the right . This is the percentage of water. To check, the two percentages should add up closely to 100%.
It is also important to discuss how probabilty is not always exact. To make the percentage more accurate, average out all of the percentages in the class.
You should enter your findings on the data form prepared for you (under Required Resources).
The actual percentage of water is 71% and land is 29%.
As students find out information on the amount of land and water, have them consider how our ideas might need to change on a variety of issues - conservation, recycling, and careers, for instance.
Duration: The ball toss, tallying, and percentage figuring can be done in a one hour class period. The input of the data on the form can be done the same day, or as a follow-up the next day. The assessment should take only 15 - 20 minutes.
Be sure to do an "HONEST" catch each time! Do not move your finger just to make your prediction more accurate.
Remember that probability is never exact, only probable!
As you find out information on the amount of land and water, think about how our ideas might need to change on a variety of issues, such as conservation, recycling, and careers.
Your son or daughter is learning the concept of land and water and how much of each covers the Earth's surface. This is a fairly abstract concept to young minds. The teacher is teaching and presenting in a variety of ways, using hands-on activities to reinforce the concept and make it more concrete.
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