Olympiad Test: Matter - 2 - Class 5 MCQ

The diagram has two boxes, one in which molecules are tightly packed and the other one in which the molecules are slightly loosely packed. Here solid is slowly converting to liquid state which occurs during melting. While, boiling is the process where a liquid turns into a gas. In this state change, particles gain enough energy to move freely and spread out, which does not match the situation described in the question.

In physical changes, the state of matter changes, but the substance itself remains the same and can be returned to its original form. This type of change is called reversible because it can be undone without altering the substance's basic nature. For example, water freezing and melting is a reversible physical change.

In the given scenario, the process shown is evaporation, where heat from the sun causes water on the ground to change from its liquid form into water vapor. Evaporation occurs at the surface of the liquid and does not require the liquid to reach its boiling point, unlike boiling, which happens throughout the liquid at a specific temperature.

The melting point is the temperature at which a solid changes into a liquid. At this temperature, the solid absorbs enough heat energy to overcome the forces holding its particles together, allowing it to melt and become a liquid.

Matter is made up of tiny particles called atoms. Atoms are the basic building blocks of matter and combine in various ways to form molecules, which in turn make up all substances.

The burning of wood is a chemical change because it results in the formation of new substances such as ash, carbon dioxide, water vapor, and other gases. This process involves a chemical reaction where the wood undergoes combustion, and it is irreversible. The original properties of the wood are completely changed.

• Statement A: Physical change is generally reversible, meaning that the substance can return to its original form (e.g., water freezing and melting).
• Statement B: Chemical change is typically irreversible, as it results in the formation of new substances that cannot easily be turned back to their original form (e.g., burning wood to form ash).

Therefore, only Statement B is true.

Water is a liquid, and liquids do not have a fixed shape. They take the shape of their container, which is why we can't make a statue out of water. A statue requires a material with a definite shape, which liquids like water do not have. Therefore, Option A is correct.

A chemical change occurs when one form of matter changes into another kind of matter. This means that the substance undergoes a transformation, creating new substances with different properties (e.g., when wood burns and changes into ash, carbon dioxide, and water).

Freezing is the process in which a liquid turns into a solid. The opposite of this is melting, where a solid turns into a liquid. Thus, when a solid melts, it transitions from a state of lower temperature to a higher one, just as freezing involves a temperature drop.

Boiling is a process that happens at a specific temperature known as the boiling point, where the liquid changes to gas throughout the entire liquid. In contrast, evaporation can occur at various temperatures below the boiling point and takes place only at the surface of the liquid.

When the jeweller melts pure gold, he is converting solid gold into liquid gold. The gold is undergoing a physical change wherein its state is being changed but it still remains as gold. Since it is pure gold, its weight in solid form is equal to that in liquid form. Thus after melting the gold, the jeweler will get the price of 100 gm of gold only.

Gases consist of particles that are very far apart and thus move easily.

As seen in the diagram, there are small water drops on the window. These water drops can be seen as a result of the conversion of water vapour in the air back into the water form. Thus this depicts the process of condensation.

Desublimation is the process where a gas (water vapor) directly changes into a solid (ice) without passing through the liquid state. This process is also known as deposition. It is the reverse of sublimation, where a solid directly turns into a gas.

The conversion of ice into water is an example of melting, which occurs when a solid (ice) absorbs heat and changes into a liquid state. Melting happens at a specific temperature known as the melting point.

A liquid has a definite volume but no definite shape. It takes the shape of its container but maintains a fixed volume. Unlike solids, which have both a definite shape and volume, liquids do not have a fixed shape, and unlike gases, they do not expand to fill the entire space.

The melting of ice is a physical change. Melting ice involves a phase change from solid to liquid but no alteration in the chemical identity of the substance, making it a physical change.

The conversion of a solid directly into a gas, without passing through the liquid state, is called sublimation. An example of this is the transformation of dry ice (solid carbon dioxide) into carbon dioxide gas.

Baking a cake involves both chemical change and irreversible change. During the baking process, ingredients undergo a chemical transformation (such as the rise due to baking powder) and produce new substances. Once the cake is baked, it cannot be returned to its original ingredients, making it an irreversible change.