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Our Stone Age ancestors chipped pieces of flint into useful tools and carved wood into statues and toys . These endeavors involved changing the shape of a substance without changing the substance itself . But as our knowledge increased , humans began to change the composition of the substances as well - clay was converted into pottery , hides were cured to make garments , copper ores were transformed into copper tools and weapons , and grain was made into bread . Humans began to practice chemistry when they learned to control fire and use it to cook , make pottery , and smelt metals . Subsequently , they began to separate and use specific components of matter .
Please check all the words that can be used instead of the target word in the same context. Note that the morphology of the target (third person singular, past tense etc.) is considered to be applied to the candidate automatically in the process of paraphrasing.