Olympiad Test: Matter - 1 - Class 5 MCQ

Intermolecular space is the space between two molecule or atom. In solids it is very little, in liquids is more the solids but less than liquids and in gases its the maximum.

The correct answer is B: Solid molecules
Explanation:

Intermolecular forces are the forces of attraction between molecules. These forces play a significant role in determining the physical properties of substances, such as boiling point, melting point, and solubility. The strength of these forces varies depending on the nature of the molecules and their arrangement.
Intermolecular forces between gas molecules:

- Gas molecules are generally far apart from each other and have weak intermolecular forces.

- The forces between gas molecules are primarily van der Waals forces, which include London dispersion forces and dipole-dipole interactions.

- These forces are relatively weak compared to other intermolecular forces.
Intermolecular forces between liquid molecules:

- Liquid molecules are closer together than gas molecules, and they have stronger intermolecular forces.

- The forces between liquid molecules can include London dispersion forces, dipole-dipole interactions, and hydrogen bonding.

- These forces are stronger than those between gas molecules but weaker than those between solid molecules.
Intermolecular forces between solid molecules:

- Solid molecules are tightly packed and have the strongest intermolecular forces.

- The forces between solid molecules can include London dispersion forces, dipole-dipole interactions, hydrogen bonding, and even metallic bonding or covalent bonding.

- These forces are much stronger than those between gas and liquid molecules.
Conclusion:

Intermolecular forces are strongest between solid molecules. This is because solid molecules are closely packed, allowing for stronger interactions between them compared to gas or liquid molecules.

Freezing and Boiling Points of Water

The freezing and boiling points of water are important properties that are commonly used in everyday life and scientific applications. Here is a detailed explanation of the freezing and boiling points of water:

Freezing Point of Water

• Water freezes when its temperature reaches 0 degrees Celsius (°C).


• At this temperature, water molecules slow down and arrange themselves in a regular pattern called a crystal lattice.


• Ice is the solid form of water that is formed when it reaches its freezing point.


• This freezing point is used as a reference point for temperature scales like the Celsius scale.

Boiling Point of Water

• Water boils when its temperature reaches 100 degrees Celsius (°C) under normal atmospheric pressure.


• At this temperature, water molecules gain enough energy to overcome the forces of attraction between them and transition from a liquid to a gas.


• The gaseous form of water is known as steam or water vapor.


• The boiling point of water is also used as a reference point on temperature scales like the Celsius scale.

Answer

The correct answer is B: 100°C.

Therefore, the boiling point of water is higher than the freezing point of water.

Explanation:
When a substance changes from a solid to a liquid, it undergoes a process called melting. This occurs when the substance is heated and the particles gain enough energy to break free from their fixed positions and move more freely. Here's a detailed explanation of each option:
A: Boiling
- Boiling occurs when a liquid changes to a gas.
- This involves the substance reaching its boiling point and the particles gaining enough energy to overcome the intermolecular forces holding them together.
B: Melting
- Melting occurs when a solid changes to a liquid.
- This happens when the substance is heated and the particles gain enough energy to overcome the forces holding them in a fixed, regular arrangement.
C: Freezing
- Freezing occurs when a liquid changes to a solid.
- This happens when the substance is cooled and the particles lose enough energy to arrange themselves in a fixed, regular pattern.
D: Sublimation
- Sublimation occurs when a solid changes directly to a gas without passing through the liquid phase.
- This happens when the substance is heated and the particles gain enough energy to break free from their fixed positions and enter the gas phase without becoming a liquid first.
Therefore, when a substance changes from a solid to a liquid, it has reached the point of melting.

Properties of Gas Molecules:
Gas molecules exhibit certain characteristics that distinguish them from molecules of other states of matter. The true statement regarding the molecules of gases is:
A: They can move around freely
Explanation:
Gas molecules possess the following properties:
- Random Motion: Gas molecules are in constant motion, moving in all directions with varying speeds. This random motion allows them to cover a large volume of space.
- No Fixed Volume: Unlike solids and liquids, gas molecules do not have a fixed volume. They can expand to fill the entire space available to them.
- No Fixed Shape: Similar to their volume, gas molecules do not have a fixed shape. They conform to the shape of their container.
- Free Movement: Gas molecules experience weak intermolecular forces, allowing them to move around freely within their container. They exhibit a high degree of mobility and can diffuse and mix with other gases easily.
Therefore, the correct statement is that gas molecules can move around freely.

Answer:
When heat is supplied to molecules, their kinetic energy increases.
Explanation:
- Heat is a form of energy that is transferred between objects or systems due to temperature differences.
- Molecules are composed of atoms held together by chemical bonds.
- When heat is supplied to molecules, it causes them to vibrate and move more rapidly.
- This increase in molecular movement results in an increase in kinetic energy, which is the energy associated with the motion of particles.
- Kinetic energy is directly proportional to the temperature of the system.
- As the molecules gain kinetic energy, they collide more frequently and with greater force, leading to an increase in temperature.
- This increase in temperature can have various effects, such as causing substances to change state (e.g., from solid to liquid) or increasing the rate of chemical reactions.
- It is important to note that while heat can increase the kinetic energy of molecules, it does not directly affect their chemical, potential, or electrical energy levels.

Statement: Pick the correct option.
Options:
- A: Solids can freeze
- B: Liquids can freeze
- C: Gases can freeze
- D: All of the above
Answer: B: Liquids can freeze
Explanation:
When considering the freezing process, it is important to understand that different states of matter have different freezing points and behaviors. Here is a detailed explanation of each option:
- A: Solids can freeze
- Solids can indeed freeze, but this option does not cover the entire range of possibilities.
- B: Liquids can freeze
- Liquids can freeze when their temperature decreases below their freezing point.
- This is a correct statement because liquids, such as water, can transform into solids (ice) when they freeze.
- C: Gases can freeze
- Gases can also freeze, but this option is not entirely accurate because freezing is typically associated with the transition from liquid to solid, not gas to solid.
- D: All of the above
- This option includes all three states of matter (solids, liquids, and gases), but it is not correct because gases do not freeze directly.
Therefore, the correct option is B: Liquids can freeze.

Molecules are the components of solids, matter, and solutions. Here's why:

• Solids: In solids, molecules are tightly packed together in a fixed structure.
• Matter: Matter, in general, is anything that has mass and takes up space, and it is composed of molecules.
• Solutions: In solutions, molecules of the solute are dispersed within the solvent.

Therefore, molecules are fundamental components of all these categories.