What can you say about the boiling points of liquids that collect at
the bottom as residue?
A. They have high boiling points
B. They have moderate boiling points
C. They have low boiling points
D. None of the above
Answers
Answer:
The Theory
What are liquids?
Liquids are one of the three states of matter. They are able to flow and occupy the shape of the container.
What happens when a liquid is heated?
As a liquid is heated, its temperature increases. As its temperature increases, the molecules of the liquid gain energy and their kinetic energy increases. As the kinetic energy increases, the molecular motion increases and the molecules of the liquid overcome the force of attraction between them.
On continuous heating, a particular temperature is reached where the molecules of the liquid leave the surface in the form of vapour. This produces a pressure above the liquid equal to the atmospheric pressure and the liquid starts boiling.
At this stage, the temperature of the liquid remains stationary even on further heating. This stationary temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure is called the boiling point of that liquid. At this temperature, bubbles begin to form and rise in the liquid. Before reaching this temperature, The bubble is not forming because the atmospheric pressure is greater than the pressure in the bubbles and they collapse.
Can you define the process of evaporation and boiling?
Evaporation and boiling are two different processes. Evaporation is a process where liquid is converted into gas at any temperature below its melting point. Boiling is the process in which liquid is converted into vapour at its boiling point. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon. Evaporation is the gradual vaporisation of a liquid on the surface Whereas the boiling is the rapid vaporisation of a liquid when it is heated to its boiling point. Below the boiling point, a liquid evaporates from its surface. At the boiling point, vapour bubbles come from the bulk of the liquid.
At an atmospheric pressure of exactly 760mm Hg (1 atm), the temperature at which a liquid boils is called the normal boiling point of the liquid. For water, the vapour pressure reaches the standard atmospheric pressure of 1 atmosphere at 100°C. So the normal boiling point of water is 100°C (212°F or 373K).The boiling point of pure water increases on the addition of soluble substances such as sugar or common salt. Boiling point of pure water increases with increase in pressure.