7 Questions
What is the purpose of placing a perforated asbestos sheet between the China dish and funnel in an experimental setup for sublimation?
To prevent direct heating of the funnel
In the experimental setup for sublimation, what would happen if the China dish was directly heated without the presence of the wire gauze?
The sublimate would not form
What substance changes directly from solid to gas without passing through the liquid state during this experiment?
Ammonium chloride
At what temperature does water start boiling in the experiment mentioned in the text?
75°C
What is the name given to the solid substance obtained by cooling the vapors in this experiment?
Sublimate
What is the purpose of the wire gauze in this experiment?
To prevent direct contact between the flame and China dish
During the sublimation process, what state change does solid ammonium chloride undergo?
Boiling
Study Notes
Change of State
- During the change of state from solid to liquid or from liquid to gas, the temperature remains constant until all the solid has melted or all the liquid has vaporized.
- The heat energy supplied is used to overcome the forces of attraction, resulting in no rise in temperature.
Sublimation
- Sublimation is the process where a substance changes directly from a solid to a gas.
- Camphor or ammonium chloride can be used to study sublimation.
- To study sublimation, crush the substance, place it in a China dish, and set up an apparatus with a funnel and cotton plug.
Melting and Boiling
- Melting is an endothermic process because heat is absorbed during this process.
- Boiling can occur at room temperature under low pressure.
- The boiling point is the temperature at which a liquid starts boiling.
- For water, the boiling point is 100°C or 373K.
Heating Experiment
- When heating ice, the temperature remains constant at 0°C until all the ice has melted.
- Once the ice is converted to water, the temperature starts rising until the water begins to boil.
- When the water starts boiling, the temperature remains constant at 100°C until all the water has changed to vapors.
Test your knowledge on heat energy absorption during the change of state from solid to liquid or liquid to gas. Check your understanding of why the temperature remains constant during these processes.
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