Matter in Various States

Match the following properties with their appropriate descriptions: Column I Column II A. Supercritical Fluid 1. Pressure of vapour in equilibrium with its liquid B. Vapour Pressure 2. Behaves like both a gas and a liquid C. Latent Heat of Fusion 3. Pressure and temperature where all states coexist D. Triple Point 4. Energy required to change a solid to liquid without temperature

1. A: 2, B: 1, C: 4, D: 3
2. A: 2, B: 3, C: 1, D: 4
3. A: 3, B: 1, C: 4, D: 2
4. A: 3, B: 4, C: 2, D: 1

Answer: (a) A: 2, B: 1, C: 4, D: 3

Imagine you are asked to identify an unknown substance. It is a solid at room temperature, sublimes directly when heated, and leaves no residue. Which of the following substances could it be?

1. Sodium chloride
2. Sulphur
3. Naphthalene
4. Hydrochloric acid

Answer: (c) Naphthalene

During an experiment, a student observed that ice cubes placed in a closed container at room temperature slowly transformed into liquid water and then into vapour. Which factor is least likely to influence the transformation?

1. Temperature of the surroundings
2. Volume of the container
3. Initial mass of the ice cubes
4. Time allowed for the process

Answer: (b) Volume of the container

A substance undergoes a phase change where the - Temperature remains constant - The interparticle forces become weaker - The particles move farther apart. Which of the following could describe this phase change?

1. Liquid freezing
2. Solid melting
3. Vapour condensing
4. Vapour undergoing deposition

Answer: (b) Solid melting

A student conducts an experiment to determine the effect of pressure on the boiling point of a liquid. The student observes that as the pressure increases, the boiling point also increases. Which of the following best explains this phenomenon?

1. Increased pressure compresses the liquid molecules, decreasing their kinetic energy.
2. Increased pressure lowers the vapour pressure of the liquid.
3. Increased pressure raises the energy required for molecules to escape the liquid phase.
4. Increased pressure reduces intermolecular forces in the liquid.

Answer: (c) Increased pressure raises the energy required for molecules to escape the liquid phase.

An industrial process involves the liquefaction of gases. Which of the following changes will increase the efficiency of the process?

1. Increasing the temperature while maintaining the same pressure.
2. Decreasing both temperature and pressure.
3. Decreasing the pressure while maintaining the same temperature.
4. Increasing the pressure while decreasing the temperature.

Answer: (d) Increasing the pressure while decreasing the temperature.

A researcher is studying the effect of temperature on the solubility of gases in liquids. It is observed that as the temperature increases, fewer gas molecules remain dissolved in the liquid. Which of the following best explains why this happens?

1. The density of the gas decreases with increasing temperature.
2. The gas molecules gain energy and escape from the liquid phase more readily.
3. The intermolecular forces between gas and liquid particles weaken with rising temperature.
4. The liquid becomes denser, reducing its capacity to dissolve gases.

Answer: (b) The gas molecules gain energy and escape from the liquid phase more readily.

Carefully read through the passage given below and answer the following questions. Advanced States of Matter In addition to solids, liquids, and gases, there are other unusual states of matter. Plasma is one of them. It forms when gases are heated to very high temperatures, causing atoms to lose their electrons. Plasma is found in stars, like the Sun, and in lightning. Another special state is the Bose-Einstein Condensate (BEC), which happens at extremely cold temperatures. In this state, particles move very slowly and combine to act like one big particle. These advanced states help scientists study important things, like how electricity can flow without resistance in superconductors or how liquids can flow without stopping in superfluids. Why does plasma conduct electricity, unlike solids, liquids, or gases?

1. Plasma is made up of neutral particles.
2. Plasma has a high density, allowing current to flow.
3. Plasma contains free electrons and ions that move freely.
4. Plasma is always hotter than solids and liquids.

Answer: (c) Plasma contains free electrons and ions that move freely.

Carefully read through the passage given below and answer the following questions. Correlation Between Molecular Structure and Macroscopic Behaviour The properties of substances we observe in daily life, like their state, hardness, or boiling point, are closely linked to their molecular structure. Molecules are made up of atoms bonded together in specific arrangements, and these bonds determine how molecules interact. For example, water is liquid at room temperature because its molecules form hydrogen bonds, which are strong enough to hold them together but allow movement. Diamond, on the other hand, is extremely hard because its carbon atoms form a rigid, three-dimensional network of strong covalent bonds. Similarly, gases like oxygen have weak intermolecular forces, allowing their molecules to move freely and spread out. By understanding molecular structures, scientists can predict and explain behaviours like solubility, melting points, and conductivity. This connection between structure and properties is fundamental in materials science and everyday applications, such as designing medicines or creating stronger materials. A gas becomes a liquid when cooled under high pressure. Which of the following properties likely changes during this process?

1. Molecular weight
2. Bond type within the molecule
3. Number of atoms per molecule
4. Intermolecular forces

Answer: (d) Intermolecular forces

Carefully read through the passage given below and answer the following questions. Correlation Between Molecular Structure and Macroscopic Behaviour The properties of substances we observe in daily life, like their state, hardness, or boiling point, are closely linked to their molecular structure. Molecules are made up of atoms bonded together in specific arrangements, and these bonds determine how molecules interact. For example, water is liquid at room temperature because its molecules form hydrogen bonds, which are strong enough to hold them together but allow movement. Diamond, on the other hand, is extremely hard because its carbon atoms form a rigid, three-dimensional network of strong covalent bonds. Similarly, gases like oxygen have weak intermolecular forces, allowing their molecules to move freely and spread out. By understanding molecular structures, scientists can predict and explain behaviours like solubility, melting points, and conductivity. This connection between structure and properties is fundamental in materials science and everyday applications, such as designing medicines or creating stronger materials. The following table lists the boiling points of some substances. What conclusion can be drawn from the data? Substance Molecular Structure Boiling Point (°C) Water Polar, hydrogen bonding 100 Methane Non-polar, weak dispersion -161 Ethanol Polar, hydrogen bonding 78

1. Substances with hydrogen bonds have higher boiling points.
2. Non-polar substances always boil at higher temperatures.
3. Boiling points are unrelated to molecular structure.
4. Polar molecules always have lower boiling points than non-polar ones.

Answer: (a) Substances with hydrogen bonds have higher boiling points.