Crystallization
This is a technique commonly done by chemists to purify compounds. During crystallization, an impure,solid compound is dissolved with a hot solvent. In the container the impurities and the needed compound move freely. When the solution cools down, the solvent can cannot hold all the solutes. Each solute will form a crystal. Therefore each crystal is made of only one molecule. Once it cools down if will be placed in a cold bath to complete the crystallization.
        
             
        
        
        
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Viruses can use energy of living cells that they infect.
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a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.
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