Explain that impurities change the melting point and boiling point of a substance.

For this page, pure substance is revised through the specific task: Explain that impurities change the melting point and boiling point of a substance. The approved objective is: Explain that impurities change the melting point and boiling point of a substance. The key evidence is single element or compound / fixed melting point, and the result to look for is purity evidence. This makes it different from nearby objectives because the answer must stay anchored to Explain that impurities change the melting point and boiling point of a substance, not another Chemical analysis test. Useful curriculum keywords include melting point and boiling point. Keep the method, observation, and conclusion separate so the answer does not confuse gas tests, flame tests, cation tests, anion tests, chromatography, pure substances, or formulations. A strong exam response states the test or measurement, describes what is seen, and then links that evidence directly to Pure substances.