Matter, Atoms & Mixtures: Class 8–9 Foundations: 18 MCQs with answers

B · Sugar particles slip into empty spaces between water particles.

Matter is made of tiny particles with empty spaces between them. Sugar particles fit into these gaps, so the level barely changes.

C · They are widely spaced and move freely at high speed.

Gas particles are far apart and move freely, which is why gases fill their container.

A · Iron ($\text{Fe}$)

An element is made of only one kind of atom. Iron contains only iron atoms; the others are compounds.

C · Water

The solvent is the substance present in larger amount that dissolves the solute. In salt water, water is the solvent and salt is the solute.

D · Filtration

Sand is an insoluble solid, so filtration separates it from water.

D · Electron

Electrons are negatively charged and orbit the nucleus.

A · True

Sodium (a reactive metal) and chlorine (a poisonous gas) combine chemically to form sodium chloride — common table salt — showing that a compound's properties differ completely from its elements.

C · Gas particles lose kinetic energy and move less, so they occupy less space.

Lower temperature means lower kinetic energy, so gas particles move less and the gas occupies less volume.

B · A compound has properties different from its constituent elements.

Sodium chloride is a compound formed by chemical combination, and its properties are completely different from those of sodium and chlorine.

A · A compound has a fixed ratio of components; a mixture has a variable ratio.

Compounds form in fixed ratios by chemical combination; mixtures have variable ratios and can be separated physically.

D · It increases, so more sugar can dissolve.

For most solids, solubility increases with temperature, so a warmed saturated solution can dissolve more solute.

D · Solubility of gases decreases as temperature rises.

Gas solubility decreases with temperature, so dissolved carbon dioxide escapes faster from warm cola.

A · Magnetic separation

Iron is magnetic and sulphur is not, so a magnet separates them without any chemical change.

D · Both A and R are true, and R correctly explains A.

Solution particles are so small that they stay dispersed and do not settle — this is exactly why a solution does not settle on standing.

D · I and III only

Statement II is false: compounds can only be separated by chemical means, not by filtration. Statements I and III are correct.

D · Sugar dissolves; melting is a heat-driven change of state, not dispersal in a solvent.

Melting is a change of state caused by heat. Dissolving is a solute dispersing through a solvent without changing state.

A · 400 grams

At 80°C, the solubility of sugar in water allows for 400 grams to dissolve in 1 liter, making it the required amount to create a saturated solution.

D · Filter the mixture to separate the sand from the salt solution.

Filtering the mixture will allow the sand (insoluble solid) to remain on the filter paper while the salt dissolves in the water, creating a solution that can be collected separately.