Olympiad Test: Matter - 1 - Class 5 MCQ

In solids, the molecules are closely packed together with very strong intermolecular forces, leaving minimal space between them. This is why solids have a fixed shape and volume. In liquids, the molecules are less tightly packed, and in gases, the molecules are far apart. Therefore, the least intermolecular space is found in solids.

The freezing point of water is 0°C, and the boiling point of water is 100°C at standard atmospheric pressure. These are the temperatures at which water changes its state from liquid to solid (freezing) and from liquid to gas (boiling). Therefore, the correct answer is Option B (100°C).

When a substance changes from a solid to a liquid, it is undergoing the melting process. This happens when the substance reaches its melting point, where it absorbs heat and the molecules gain enough energy to move freely, transitioning into the liquid state.

In gases, the molecules are widely spaced and have high energy, allowing them to move freely in all directions. This freedom of movement causes gases to expand and fill any available space, unlike solids and liquids, which have fixed shapes and volumes.

When heat is supplied to molecules, their kinetic energy increases. The added heat causes the molecules to move faster, which increases their motion and energy. This is why substances expand or change state as they absorb heat.

All three, steam, oxygen, and carbon dioxide, can be compressed.

• Steam is a gas and, like any gas, can be compressed by reducing the volume and increasing the pressure.
• Oxygen is a gas and can also be compressed under pressure.
• Carbon dioxide is a gas and can be compressed into a liquid or solid form under high pressure.

Therefore, the correct answer is Option D (P, Q and R).

• A: Solids can freeze - Solids are already in a frozen state, so this statement is not about freezing but rather about maintaining their solid form.
• B: Liquids can freeze - This is the correct statement because liquids freeze when the temperature drops below their freezing point, turning into solids (like water freezing into ice).
• C: Gases can freeze - Gases can indeed turn into solids under extreme conditions, but freezing is generally associated with the liquid-to-solid phase change.
• D: All of the above - This option includes gases, which do not typically freeze in the common sense of the term.

Therefore, Option B is the correct choice, as liquids can freeze when cooled below their freezing

Both water vapor and steam are gases, meaning they have no definite shape and no definite volume. They expand to fill any container they are in. While steam is water in its gaseous state, water vapor refers to the gas phase of water that is below its boiling point. Therefore, both have the characteristics of gases.

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.

The ability of liquids to flow is due to the fact that their particles are not tightly packed like in solids. The particles have enough space between them to move or slide past each other, allowing the liquid to flow and take the shape of its container. This is a key characteristic of liquids.