Scientists use what is called the scientific method. 

• First you need a question which you want answered.  Scientists call these questions hypotheses. 
  
  
• Second, you develop an experiment to test your question or hypotheses. 
  
  
• Third, and last, you examine the data from your  experiment and answer the hypothesis (question) yes or no. 

  A simple example hypothesis would be - Do plants need water to grow? 

The experiment could be as follows, grow 5 plants with water and 5 plants without water.  After several days you observe the plants without water are dead.  The answer is yes , plants need water to grow.  Why grow five plants?  Why not just one?  Think about that one.

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