Question 1
Question: A substance has a definite volume but no definite shape. State whether this substance is a solid, liquid or a gas.
Answer: The substance is a liquid. It has a definite volume but no definite shape and takes the shape of the container in which it is placed
Question 2
Question: A small quantity of a gas is let into a large evacuated chamber. a) How much of the chamber gets filled with the gas? b) What property of the gas helps it to do so?
Answer: a) The entire chamber gets filled with the gas. b) The gas molecules have very weak intermolecular forces of attraction. This permits the gas molecules to diffuse and fill up the entire chamber.
Question 3
Question: Why do solids not diffuse into one another?
Answer: Solids have very little intermolecular spaces, there by not allowing the molecules of another solid to enter. Moreover, the intermolecular force of attraction between molecules of one solid is very high and this prevents diffusion of molecules of one solid into another solid.
Question 4
Question: What is matter? How is it classified?
Answer: Matter is anything that occupies space, possesses mass, offers resistance and can be felt by one or more of our senses. Matter may be classified as shown below:
Question 5
Question: Among solids, liquids and gases which one has the maximum movement of molecules, the maximum intermolecular attraction and the minimum space between molecules.
Answer: Maximum movement of molecules is seen in gases Maximum intermolecular attraction is found in solids Minimum space between molecules occur in solids
Question 6
Question: Name the properties that decide whether a given substance exists as a solid, liquid or a gas.
Answer: The properties are:
- Space between molecules
- Force of attraction between molecules
- The kinetic energy of molecules
Question 7
Question: List two properties that liquids have in common with gases.
Answer: Two common properties shared by liquids and gases are i) Gases and liquids do not have a fixed shape ii) Gases and liquids flow easily
Question 8
Question: What happens when a liquid is heated?
Answer: The heat is absorbed by the liquid has the following effects:
- It increases the average kinetic energy of the particles in the liquid, increasing its temperature.
- It furnishes energy for the particles to pass from liquid to vapour state. As heating continues and temperature approaches the boiling point, more and more energy is utilised for vapourising the liquid and less and less for raising the temperature.
Question 9
Question: Why does water boil at a lower temperature at higher altitudes?
Answer: Boiling occurs at a point where vapour pressure is equal to the external atmospheric pressure. At higher altitudes atmospheric pressure is much less. Less thermal energy is required to get vapour pressure equal to the atmospheric pressure. Example: cooking of potatoes take much longer at the top of a mountain because boiling temperature of water is lower.
Question 10
Question: What is the principle used in a pressure cooker?
Answer: The pressure in the enclosed volume above the liquid reaches much greater values than atmospheric pressure, thus the temperature of boiling water within the cooker is greater than the normal boiling temperature. Hence, things cook much faster.
