Test: Solids, Liquids & Gases - 2 - Class 5 MCQ

Freezing is the process in which a liquid cools down and loses energy, causing its molecules to move closer together and arrange themselves into a fixed structure, forming a solid.

Solids have a definite shape and volume

Melting is the process of changing a solid into liquid when heating.

Evaporation of water is a physical change as it only changes the state of water from liquid to gas and can be reversed by condensation.

Souring of milk is a chemical change as it results in the formation of new substances like lactic acid, and cannot be reversed.

The liquids that mix with each other are called miscible liquids.

 When a substance is heated, the intermolecular space between molecules increases due to the rapid vibration of the molecules.

Freezing of water is a physical change as it only changes the state of water from liquid to solid and can be reversed by melting

- Sugar can dissolve in water because it is a polar substance. Water, a polar solvent, effectively interacts with the sugar molecules, breaking them apart and distributing them evenly throughout the solution.
- Sand, oil, and plastic do not dissolve in water. Sand is non-polar and too large in particle form. Oil is also non-polar and does not mix with polar substances like water. Plastic does not dissolve due to its hydrophobic properties and stable molecular structure.

Explanation: When water is boiled, the temperature increases, causing the solubility of gases in water to decrease. As a result, the dissolved gases (like oxygen and carbon dioxide) are released and escape into the air as bubbles. This is why you see bubbles form and rise to the surface when water is heated or boiled.

When a substance is heated, it expands. Thus, when the tight metal lid of a jar is dipped in hot water, it expands a little, making it easier to open.

In the summer season, due to the heat, the electric wires between electric poles expand and become loose.

Burning of matchsticks is a chemical change as it results in the formation of new substances like ash and gases, and cannot be reversed.

Converting ice to water: There is no change in the chemical composition of water. The process is reversible and ice can be obtained back by freezing. Thus it is clear that it is a physical change.

When a substance is cooled, the movement of molecules slows down, and the intermolecular space between molecules decreases.