Chapter 1: Matter (DK014)

Which of the following is a pure substance?

• Sea water

• Air

• Steel

• Diamond

Which type of matter is characterized by having a definite shape and definite volume?

• Solid

• Liquid

• Gas

• Plasma

Which of the following is an example of a homogeneous mixture?

• Salad

• Vinegar

• Sand and salt mixture

• Oil and water

Answer explanation

Vinegar is a solution, which is a mixture of acetic acid and water. They mix homogeneously.

Which of the following changes represents a chemical change?

• Melting of ice

• Dissolving sugar in water

• Rusting of iron

• Boiling of water

Answer explanation

Rusting of iron is a chemical change due to the reaction of iron, Fe with water to form rust, Fe³⁺.

Which of the following statements is true about elements and compounds?

• Elements can be broken down into simpler substances by chemical means.

• Compounds are made up of two or more elements chemically combined in a fixed ratio.

• Elements and compounds both consist of one type of atom.

• Compounds can be separated into their constituent elements by physical means.

Which of the following can be separated into its components by physical means?

• Element

• Compound

• Homogeneous mixture

• Pure substance

Which of the following is an example of a compound?

• Helium

• Water

• Brass

• Oxygen

Which statement best defines the relative atomic mass of an element?

• The mass of an atom compared to one-twelfth the mass of a carbon-12 atom.

• The mass of an atom in atomic mass units (a.m.u).

• The average mass of the isotopes of an element.

• The mass of the most abundant isotope of an element.

What is the relative molecular mass of water (H₂O)? (Given: H = 1, O = 16)

• 18

• 17

• 34

• 32

Given the isotopes of magnesium ²⁴Mg, ²⁵Mg and ²⁶Mg with respective abundances of 79%, 10%, and 11%, calculate the average atomic mass of magnesium.

• 24.0 a.m.u

• 24.3 a.m.u

• 25.0 a.m.u

• 26.0 a.m.u