Man-Made Materials — Set 5

Correct Answer: C. Calcium Sulfate Hemihydrate

The correct answer is 'Calcium Sulfate Hemihydrate'. Plaster of Paris is formed by heating gypsum to a temperature of 373 K. When mixed with water, it rehydrates and sets into a hard solid mass of gypsum. It is used by doctors to support fractured bones in the right position.

Correct Answer: C. Tincture of Iodine

Tincture of iodine is a solution of 2-3% iodine in an alcohol-water mixture. It is effective at killing a wide range of bacteria and viruses on the skin. Iodine has been a standard antiseptic for over a century.

Correct Answer: A. Acrylic

Acrylic fibers are marketed under various brand names like Orlon due to their wool-like characteristics. They are synthesized from the monomer acrylonitrile. These fibers are resistant to sunlight and weather, making them good for outdoor use.

Correct Answer: C. Teflon

Teflon is a brand name for PTFE, famous for its non-stick properties. It is extremely unreactive because of the strong bond between carbon and fluorine atoms. It is used in everything from frying pans to high-performance aerospace parts.

Correct Answer: C. Neon

Neon gas emits a brilliant red-orange color when an electric discharge is passed through it at low pressure. Other gases or tinted tubes are used to create different colors in the signs. These are known as cold-cathode gas-discharge lights.

Correct Answer: C. Sodium Carbonate

Sodium carbonate, or soda ash, acts as a flux in the glass-making process. It reduces the temperature required to melt the sand, saving energy. However, it makes the glass water-soluble, so lime is added to provide durability.

Correct Answer: A. Solid Carbon dioxide

Dry ice is carbon dioxide in its solid form, which exists at temperatures below -78.5 degrees Celsius. It undergoes sublimation, turning directly from a solid to a gas without becoming a liquid. It is widely used for cooling and creating special effects.

Correct Answer: B. Graphite and Clay

Graphite is a form of carbon that leaves a mark on paper because its layers slide off easily. Clay is added to the graphite to adjust the hardness of the pencil. Despite the name, no actual lead metal is used in modern pencils.

Correct Answer: C. Anthracite

Anthracite contains the highest percentage of carbon (over 86%) and the fewest impurities. It burns with a clean, blue flame and produces the most heat per unit weight. It is the hardest and oldest form of coal found in nature.

Correct Answer: D. Silver Nitrate

Silver nitrate reacts with the salt on the skin to form silver chloride, which turns black when exposed to light. This stain cannot be washed off and only disappears as the skin cells naturally shed. It has been used for decades to prevent multiple voting.