Chemistry Ix Chapter 5 MCQs

The statement "They move at great speeds" is not correct. In a solid, the particles are closely packed and have a fixed position due to strong intermolecular forces. While they do vibrate in their fixed positions, they do not move at great speeds like particles in a gas or liquid.

Crystalline solids typically have a well-defined shape, orderly arrangements of atoms, and repeating three-dimensional arrangements of particles. However, they are not generally soft. Softness is a property associated with amorphous solids, which lack the long-range order and regular arrangement of particles found in crystalline solids.

At 100 oC, bromine is in the gas state. This is because the boiling point of bromine is 59 oC, which means that it will start to vaporize and turn into a gas at temperatures higher than this. Therefore, at 100 oC, bromine will be in the form of a gas.

At 25 oC and 1 atm, acetone is in its liquid state. This is because the boiling point of acetone is 54 oC, which is higher than the given temperature of 25 oC. Therefore, acetone does not reach its boiling point and remains in its liquid state at this temperature and pressure.

The correct answer is Nitrogen (-196 oC). This is because the given information states the bowling points of different elements, and Nitrogen has the lowest boiling point among the given elements. Boiling point is the temperature at which a substance changes from a liquid to a gas, and the lower the boiling point, the easier it is for a substance to vaporize. Therefore, Nitrogen, with a boiling point of -196 oC, is the element that vaporizes the easiest among the given options.

Substance A has a melting point of 36°C and a boiling point of 130°C. Since the melting point is higher than room temperature, it means that substance A is solid at room temperature.

When water boils, it undergoes a phase change from liquid to gas. This phase change occurs when the vapor pressure of the liquid becomes equal to the atmospheric pressure. Normally, at room temperature, the atmospheric pressure is higher than the vapor pressure of water, so it remains in its liquid state. However, by decreasing the external pressure, the vapor pressure required for boiling can be reached at room temperature, causing the water to boil. Therefore, decreasing the external pressure is the variable that would allow water to boil at room temperature.

The data in the options suggests a relationship between X and 1/Y. In all the options, the value of X/Y is the same, indicating that X is proportional to 1/Y. This means that as the value of X increases, the value of 1/Y decreases, and vice versa. Therefore, the correct answer is X ∝ 1/Y.

When the mixture of gases is heated by 20°C, the only element that will still be in a liquid state is Xenon. This is because Xenon has a boiling point of -108.1°C, which is much lower than the increased temperature of -190°C. Oxygen, argon, and hydrogen will all transition into a gaseous state at this higher temperature.

A liquid boils when its boiling point becomes equal to the pressure exerted by the surrounding atmosphere. In this case, the correct answer is 1 Pa, which is a unit of pressure. When the boiling point of a liquid matches the pressure of 1 Pascal, it will start to boil and convert into a gas.

When a substance undergoes melting, it changes from a solid state to a liquid state. During this process, the particles in the substance gain energy and start moving more freely, which causes an increase in their speed. Therefore, the correct answer is not Melting.