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Hello there, to distinguish between the pure and impure substances, it is good to check for the following.
A pure substance is made of only one element or compound. In most cases they have a sharp boiling point. For example water, whose boiling point is 100 degrees Celsius.Pure compounds cannot be separated through physical means.
For impure substances, they are made of several elements or compounds. Their boiling point is not sharp. For example, muddy water boils at temperatures below 100-degree Celsius since impurities lower the boiling point. The impure substances can be separated by a physical method. For example a mixture of iron fillings and copper sulphate granules. You can separate them physically using a magnet,
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