The readings and follow-up activities in this unit focus on two different ways in
which the forces of nature can be dangerous to humans—lightning storms and
killer bees. Chapter 9 is about lightning. Here are some additional interesting
facts about lightning storms:
• A typical lightning bolt lasts about a quarter of a second and consists of
three or four individual discharges called strokes. The average lightning
stroke is six miles long.
• Thunder is formed from the shock wave created by the rapid heating of the
air along the path of the return stroke.
• The sound of thunder travels about one mile every five seconds. When you
see a flash of lightning, count the seconds until you hear thunder. A time
lapse of ten seconds means that the strike was two miles away.
Warm-up You may start the lesson in one of the following ways:
• Rub a balloon on a piece of wool fabric and place the side you rubbed
against the wall. The balloon will stick to the wall. Explain that the negative
charges on the balloon and the positive charges on the wall attract each
other. In the same way, the negative charge on a cloud is attracted to the positive
charge on the surface of the earth. However, instead of the cloud and
the earth moving toward each other, the electricity jumps from the cloud to
the earth. Use a simple drawing on the board to illustrate the lightning bolt.
• Write the word lightning on the board, and then draw a chart with three
columns. Add the headings “Things I am sure about,” ”Things I am not sure
about,” “Things I don’t know.” Have students call out facts about lightning
and assign them to one of these columns. Then see if these facts are confirmed
in the reading passage. If not, you may
The readings and follow-up activities in this unit focus on two different ways in
which the forces of nature can be dangerous to humans—lightning storms and
killer bees. Chapter 9 is about lightning. Here are some additional interesting
facts about lightning storms:
• A typical lightning bolt lasts about a quarter of a second and consists of
three or four individual discharges called strokes. The average lightning
stroke is six miles long.
• Thunder is formed from the shock wave created by the rapid heating of the
air along the path of the return stroke.
• The sound of thunder travels about one mile every five seconds. When you
see a flash of lightning, count the seconds until you hear thunder. A time
lapse of ten seconds means that the strike was two miles away.
Warm-up You may start the lesson in one of the following ways:
• Rub a balloon on a piece of wool fabric and place the side you rubbed
against the wall. The balloon will stick to the wall. Explain that the negative
charges on the balloon and the positive charges on the wall attract each
other. In the same way, the negative charge on a cloud is attracted to the positive
charge on the surface of the earth. However, instead of the cloud and
the earth moving toward each other, the electricity jumps from the cloud to
the earth. Use a simple drawing on the board to illustrate the lightning bolt.
• Write the word lightning on the board, and then draw a chart with three
columns. Add the headings “Things I am sure about,” ”Things I am not sure
about,” “Things I don’t know.” Have students call out facts about lightning
and assign them to one of these columns. Then see if these facts are confirmed
in the reading passage. If not, you may
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