Elements, compounds and mixtures Quiz - ICSE Class 7 Science

Free practice quiz: Elements, compounds and mixtures (ICSE Class 7 Science). 51 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. Which of the following is an element that exists as a diatomic molecule at room temperature and pressure?

   1. Sulfur
   2. Phosphorus
   3. Oxygen
   4. Carbon
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   Answer: C. Oxygen

   Oxygen (O₂) is a diatomic molecule, meaning it exists as two oxygen atoms bonded together. Sulfur and phosphorus typically exist as polyatomic molecules (e.g., S₈, P₄), and carbon exists as single atoms in its elemental form (like graphite or diamond).

2. Which of the following is an example of a compound?

   1. Air
   2. Bronze
   3. Carbon dioxide
   4. Milk
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   Answer: C. Carbon dioxide

   Carbon dioxide (CO₂) is formed by the chemical combination of carbon and oxygen in a fixed ratio. Air is a mixture of gases, bronze is an alloy (a mixture of metals), and milk is a complex mixture.

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

   1. Vegetable soup
   2. Salad dressing
   3. Steel
   4. Soil
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   Answer: C. Steel

   Steel is an alloy, which is a solid solution of metals (primarily iron and carbon). Its components are evenly mixed. Vegetable soup, salad dressing, and soil are all heterogeneous mixtures with non-uniform composition.

4. Which separation technique is based on the difference in solubility of components in a solvent?

   1. Filtration
   2. Evaporation
   3. Crystallization
   4. Distillation
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   Answer: C. Crystallization

   Crystallization is a process where a solid forms crystals from a solution, melt, or gas. It's often used to purify compounds and relies on the difference in solubility of the compound and impurities at different temperatures.

5. The separation of dissolved solids from a liquid by heating the liquid to vaporize it and then cooling the vapor to condense it back into liquid form is known as:

   1. Filtration
   2. Evaporation
   3. Distillation
   4. Sublimation
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   Answer: C. Distillation

   This process accurately describes distillation, which is used to separate substances based on their different boiling points.

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