Question 29: Vinh conducts an experiment as follows: You use a distillation device to bring 100 ml of water to a boil, then lead the steam through the cooling system so that it condenses to form distilled water. You put distilled water into four cups, 20ml each. Next, you put in cups 1, 2, 3, 4 respectively 2, 4, 6, 8 g of salt and stir well. You notice: From the results of the experiment above, answer the following question: How to identify a pure substance?

Question 29: Vinh conducts an experiment as follows: You use a distillation device to bring 100 ml of water to a boil, then lead the steam through the cooling system so that it condenses to form distilled water. You put distilled water into four cups, 20ml each. Next, you put in cups 1, 2, 3, 4 respectively 2, 4, 6, 8 g of salt and stir well. You notice: From the results of the experiment above, answer the following question: How to identify a pure substance?

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