Elements, Compounds and Mixtures Quiz - ICSE Class 8 Science

Free practice quiz: Elements, Compounds and Mixtures (ICSE Class 8 Science). 50 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. Which of the following is a pure substance that cannot be broken down into simpler substances by chemical means?

   1. Compound
   2. Element
   3. Mixture
   4. Solution
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   Answer: B. Element

   An element is defined as a pure substance consisting only of atoms that all have the same number of protons in their atomic nuclei. It cannot be broken down into simpler substances by chemical means. Compounds are formed from two or more elements chemically bonded, and mixtures are physical combinations of substances.

2. Which of the following is NOT a physical property of metals?

   1. Good conductors of heat and electricity
   2. Malleable
   3. Ductile
   4. Dull appearance
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   Answer: D. Dull appearance

   Most metals have a shiny (lustrous) appearance. They are generally good conductors of heat and electricity, malleable (can be hammered into thin sheets), and ductile (can be drawn into wires).

3. Which of the following is a compound made up of only one type of atom?

   1. Water
   2. Salt
   3. Oxygen gas (O2)
   4. Carbon dioxide
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   Answer: C. Oxygen gas (O2)

   Oxygen gas (O2) is made up of two oxygen atoms bonded together, but it is still considered an element because it consists of only one type of atom. Water, salt, and carbon dioxide are compounds made of different types of atoms.

4. Which of the following is a property of gases?

   1. They have a definite shape and volume.
   2. They have a definite volume but take the shape of their container.
   3. They have no definite shape or volume and fill the entire container.
   4. They are generally incompressible.
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   Answer: C. They have no definite shape or volume and fill the entire container.

   Gases have particles that are far apart and move randomly, meaning they have neither a fixed shape nor a fixed volume. They expand to fill any container they are in.

5. Which of the following is a characteristic of ionic compounds?

   1. They have low melting and boiling points.
   2. They conduct electricity in the solid state.
   3. They are generally soluble in water.
   4. They are formed by sharing of electrons.
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   Answer: C. They are generally soluble in water.

   Many ionic compounds are soluble in water, a polar solvent, due to the electrostatic attraction between the ions and the polar water molecules. Ionic compounds typically have high melting and boiling points, conduct electricity when molten or dissolved in water (because the ions are free to move), and are formed by the transfer of electrons, not sharing.

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