Pure Substances Quiz
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5 questions, one answer each
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1. What is the chemistry definition of a pure substance?
- A. Any substance that is safe to eat or drink
- B. A single element or compound with nothing else mixed in
- C. Any liquid that looks clear
- D. A substance made entirely in a laboratory
2. How does a pure substance typically melt?
- A. Gradually over a wide range of temperatures
- B. Sharply, at one fixed temperature
- C. Only when boiled first
- D. At a temperature that varies randomly each time
3. A sample melts gradually between 110 degrees C and 118 degrees C, whereas the pure substance's known melting point is 120 degrees C. What does this suggest about the sample?
- A. The sample is pure
- B. The sample is impure
- C. The thermometer is broken
- D. The sample is a different pure substance entirely
4. Why is purity testing important for medicines?
- A. It makes the medicine taste better
- B. It has no real importance for medicines
- C. Impurities can affect safety and how well the drug works
- D. It only matters for food, not drugs
5. Two effects of an impurity on a substance's melting behaviour are usually described together. What are they?
- A. Raises the melting point and narrows the range
- B. Lowers the melting point and widens the range
- C. Has no effect on melting point or range
- D. Raises the boiling point only