science videos for middle school

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1:10:21

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32:09

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57:53

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3:45

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9:52

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38:08

5:56

3:26

5:42

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1:45

6:45

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11:50

11:37

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2:58

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52:07

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9:27

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23:46

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44:25

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6:21

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