Questions and Answers
Which term is used to describe the process where a solid changes directly to a gas?
Sublimation
Which of the following accurately describes the temperature at which a liquid turns into a gas?
Boiling point
At what temperature does pure water freeze under normal atmospheric conditions?
0°C
What happens to a substance at its freezing point?
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Which statement is correct about the melting point of a pure substance?
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Study Notes
Changes in State
- Sublimation is a process where a solid changes directly to a gas or vice versa, without going through the liquid phase.
Melting and Freezing
- A pure substance melts at a specific temperature, known as the melting point (m.p).
- The melting point is the same temperature at which a liquid freezes, known as the freezing point (f.p).
- The melting and freezing points of a substance are always the same temperature.
- For example, pure water melts and freezes at 0°C.
Changes of Physical State
- Large changes in temperature and pressure can cause a substance to change its physical state.
- The changes between solid, liquid, and gas states can occur by raising or lowering the temperature of the substance at atmospheric pressure.
Melting and Boiling Points
- The melting point (m.p) is the temperature at which a solid turns into a liquid.
- The boiling point (b.p) is the temperature at which a liquid turns into a gas.
- The melting point and freezing point have the same value, while the boiling point is a separate value for a substance.
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