Which statement about the melting point of a substance is correct?
A - OCR Gateway - GCSE Chemistry - Question 9 - 2021 - Paper 1
Question 9
Which statement about the melting point of a substance is correct?
A. A pure substance has a sharp melting point.
B. A pure substance melts over a range of temperatu... show full transcript
Worked Solution & Example Answer:Which statement about the melting point of a substance is correct?
A - OCR Gateway - GCSE Chemistry - Question 9 - 2021 - Paper 1
Step 1
A. A pure substance has a sharp melting point.
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Answer
This statement is correct. Pure substances melt at a specific temperature, which is known as the melting point. Unlike impure substances, which can melt over a range of temperatures, pure substances transition from solid to liquid at a definite temperature.
Step 2
B. A pure substance melts over a range of temperatures.
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Answer
This statement is incorrect. A pure substance has a specific melting point, not a range. A mixture, however, may melt over a range of temperatures.
Step 3
C. The melting point of an impure substance is higher than a pure substance.
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This statement is false. Generally, the melting point of an impure substance is lower than that of a pure substance due to the presence of impurities which disrupt the orderly structure needed for melting.
Step 4
D. The melting point of a pure substance is higher than the boiling point.
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Answer
This statement is incorrect. The boiling point of a substance is typically higher than its melting point. For example, water melts at 0°C and boils at 100°C under standard atmospheric pressure.
