Question 1

Which of the following is considered a pure substance in chemistry?

Accepted Answer

Distilled water. Distilled water consists only of water molecules and has a fixed composition. Pure substances cannot be separated into other kinds of matter by any physical process. It is distinct from mixtures like air or milk which contain multiple components.

Question 2

What type of mixture is a solution of sugar in water?

Accepted Answer

Homogeneous. A sugar solution is a homogeneous mixture because its composition is uniform throughout. The particles are distributed at the molecular level and do not settle over time. Such mixtures are also simply called true solutions.

Question 3

Which state of matter has a definite shape and a definite volume?

Accepted Answer

Solid. Solids have a definite shape and volume due to the strong intermolecular forces between particles. The particles are closely packed and can only vibrate about their fixed positions. This rigidity makes them incompressible under normal conditions.

Question 4

The process of a solid changing directly into a gas is called?

Accepted Answer

Sublimation. Sublimation occurs when a substance transitions from a solid state to a gaseous state without passing through the liquid phase. Common examples include dry ice and naphthalene balls. This process happens when the vapor pressure of the solid exceeds the atmospheric pressure.

Question 5

Which of the following is a characteristic of a compound?

Accepted Answer

Chemical bond formation. A compound is formed when two or more elements combine chemically in a fixed ratio. The properties of a compound are entirely different from its constituent elements. Energy is usually absorbed or evolved during the formation of a compound.

Matter & Mixtures — Set 1