All Free Everyday Science MCQs with Answers

491. Which is the purest form of water?

• A. Rain water
• B. Heavy water
• C. Tap water
• D. None of these

Explanation: Rainwater is generally regarded as the purest naturally occurring water among these choices because it forms through condensation and has not yet passed through soil or pipelines. It can still collect dust and gases while falling, so distilled water would be purer if it were listed.

492. Mohs' Scale" is used to indicate the_________?

• A. Degree of hardness of minerals
• B. Degree of viscosity of a liquid
• C. Degree of elasticity of a material
• D. Degree of brittleness of a substance

Explanation: The Mohs scale ranks minerals by their resistance to scratching, from talc at 1 to diamond at 10. It measures hardness, not viscosity, elasticity, or brittleness.

493. Which gas is used in preparation of Soda water?

• A. Ammonia
• B. Hydrogen
• C. Nitrogen
• D. Carbon Dioxide

Explanation: Carbon dioxide is dissolved under pressure to make soda water fizzy; the released gas forms the bubbles. Ammonia, hydrogen and nitrogen are not the usual gas used for carbonation.

494. Who invented "Aspirin" in 1897?

• A. Barnard
• B. Newton
• C. Felix Hoffmann
• D. McLeod

Explanation: Felix Hoffmann prepared acetylsalicylic acid, marketed as aspirin, at Bayer in 1897. The name aspirin refers to this specific compound, not to a general painkiller discovered by Newton or McLeod.

495. Which of the following cannot be stored in glass bottle?

• A. Aqua regia
• B. HF
• C. HCL
• D. HBr

Explanation: Hydrofluoric acid reacts with silica, the main component of ordinary glass, so it cannot safely be stored in glass bottles. It is usually kept in plastic containers.

496. Soap is ______?

• A. Acid
• B. Chemical
• C. Powder
• D. Salt

Explanation: Soap is chemically a salt formed from fatty acids and an alkali, such as sodium or potassium hydroxide. It is not itself an acid, although it is commonly sold as a solid or powder.

497. Which are the only two elements on the periodic table that are liquid at room temperature?

• A. Mercury and Bromine
• B. Carbon and helium
• C. Nitrogen and Hydrogen
• D. Oxygen and Neon

Explanation: Mercury and bromine remain liquid near ordinary room temperature, unlike most elements, which are solid or gaseous. Bromine is the only nonmetal among the two.

498. Diamonds are made up almost entirely of what element?

• A. Carbon
• B. Helium
• C. Methane
• D. Nitrogen

Explanation: Diamond is a crystalline form of carbon in which each carbon atom is strongly bonded to four others. Its hardness comes from this three-dimensional bonding arrangement, not from methane or nitrogen.

499. What is the first element in the periodic table?

• A. Hydrogen
• B. Helium
• C. Nitrogen
• D. Carbon

Explanation: Hydrogen has atomic number 1, so it occupies the first position in the periodic table. Helium follows it at atomic number 2.

500. what is anthracite?

• A. Carbon
• B. Hard coal
• C. Ammonia
• D. None of these

Explanation: Anthracite is the hardest and highest-grade form of coal, containing a high percentage of carbon and relatively little moisture. It burns with more heat and less smoke than softer coal.