Online Test — Is Matter Around Us Pure
18 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 18
Which of the following is a pure substance?
Air
Sugar solution
Distilled water
Milk
Explanation: Distilled water is made of only one kind of particle with fixed composition, so it is a pure substance.
Question 2 of 18
A homogeneous mixture of two or more substances is called a:
suspension
solution
colloid
compound
Explanation: A solution is a homogeneous mixture with uniform composition throughout.
Question 3 of 18
In a salt solution, the solute is:
water
salt
the beaker
air
Explanation: The dissolved component present in smaller amount is the solute; here it is salt.
Question 4 of 18
30 g of solute in 120 g of solution gives a mass percentage of:
20%
25%
30%
40%
Explanation: (30 / 120) x 100 = 25%.
Question 5 of 18
The Tyndall effect is shown by:
a true solution
a colloid
distilled water
a clear salt solution
Explanation: Colloidal particles (1-100 nm) scatter light, making the beam visible.
Question 6 of 18
Particles in a suspension are:
less than 1 nm
1 to 100 nm
more than 100 nm
the same size as solution particles
Explanation: Suspension particles are larger than 100 nm, so they settle and can be filtered.
Question 7 of 18
Two immiscible liquids are separated using a:
condenser
separating funnel
fractionating column
centrifuge
Explanation: A separating funnel lets the denser liquid run off first; the lighter layer is collected next.
Question 8 of 18
Which substance can be separated by sublimation from common salt?
Sand
Sugar
Ammonium chloride
Iron filings
Explanation: Ammonium chloride sublimes on heating while salt does not, so sublimation separates them.
Question 9 of 18
Cream is separated from milk by:
filtration
centrifugation
distillation
crystallisation
Explanation: Centrifugation spins out the fine, less dense cream that cannot be filtered.
Question 10 of 18
Acetone and water (boiling points 56 C and 100 C) are best separated by:
a separating funnel
simple distillation
sublimation
centrifugation
Explanation: They are miscible and their boiling points differ by more than 25 C, so simple distillation works.
Question 11 of 18
The gases of air are separated by:
evaporation
fractional distillation
chromatography
filtration
Explanation: Air is liquefied and warmed in a fractionating column; the gases boil off in order of boiling point.
Question 12 of 18
Chromatography is used to separate:
oil from water
salt from sand
different colours in a dye
iron from sulphur
Explanation: Chromatography separates components dissolved in the same solvent that travel at different rates.
Question 13 of 18
Which of the following is a chemical change?
Melting of ice
Dissolving sugar
Burning of a candle
Boiling water
Explanation: Burning forms new substances with heat and light, so it is a chemical change.
Question 14 of 18
An element that cannot be broken into anything simpler is made of:
two kinds of atoms
only one kind of atom
molecules of a compound
a mixture of metals
Explanation: An element is a pure substance made of only one kind of atom.
Question 15 of 18
Which of these is a metalloid?
Copper
Sulphur
Silicon
Oxygen
Explanation: Silicon shows properties between metals and non-metals, so it is a metalloid.
Question 16 of 18
After heating iron filings with sulphur, the product iron sulphide is:
attracted by a magnet
a mixture
a compound with new properties
easily separated by hand
Explanation: Heating combines them chemically into FeS, a compound that is no longer magnetic.
Question 17 of 18
Which statement is true for a mixture?
It has a fixed composition by mass
Its components keep their own properties
It can be separated only chemically
It always forms with heat or light
Explanation: A mixture has a variable composition and its components keep their own properties; it is separated physically.
Question 18 of 18
The maximum mass of a solute that dissolves in 100 g of solvent at a given temperature is its:
concentration
solubility
mass percentage
volume percentage
Explanation: This defines solubility, which usually increases with temperature for solids.