CBSE Class 7 Science Advanced Chemistry Chemistry in Daily Life MCQs Set 03

Answer: (a) Quinine

Explanation:
1. Quinine is obtained from the bark of the cinchona tree and is used to treat malaria.
2. Tetracycline, penicillin and sulfadiazine are antibiotics or sulpha drugs used against bacterial infections.
3. The answer is quinine.

Teacher's Note:
1. Bark of the cinchona tree gives the antimalarial drug.
2. Penicillin comes from a mould, not from bark.

Answer: (b) CDBAE

Explanation:
1. RCC is concrete reinforced with steel, used for bridges: (C).
2. Cement mortar joins bricks and is used for plastering: (D).
3. Cement mixed with water fills gaps in construction: (B).
4. Bricks form the walls of buildings: (A).
5. Concrete is cast into roofs, pillars and beams: (E).
6. The order is C, D, B, A, E: option (b).

Teacher's Note:
1. RCC means reinforced cement concrete, so it has the steel.
2. Mortar is the sticky mix between bricks.

Answer: (b) copper

Explanation:
1. Brass (copper and zinc) and bronze (copper and tin) are both mostly copper.
2. They are used for switches, taps, statues, coins and utensils.
3. The element is copper.

Teacher's Note:
1. Find the metal common to brass and bronze.
2. Copper is the major metal of both.

Answer: (a) FDBCAE

Explanation:
1. Gold is yellow and soft, used in jewellery: (F).
2. Copper is reddish brown and is used in cables: (D).
3. Iron (as steel) is used in buildings and bridges: (B).
4. Lead is the silvery grey metal used to cover roofs: (C).
5. Zinc is bluish white and coats iron articles: (A).
6. Aluminium is silvery white and used for food packing: (E).
7. The order is F, D, B, C, A, E: option (a).

Teacher's Note:
1. Colours are the best clue: gold yellow, copper reddish brown.
2. Zinc coats iron in galvanization.

Answer: (b) Soaps do not form lather with hard water but form curdy precipitates.

Explanation:
1. Soaps are sodium or potassium salts of fatty acids, not of alkyl hydrogen sulphates (those are detergents), so (a) is wrong.
2. Soaps give curdy scum (precipitates) with hard water and no lather, so (b) is right.
3. Detergents are generally not biodegradable and do not form scum, so (c) and (d) are wrong.
4. The answer is (b).

Teacher's Note:
1. Scum is the curdy white solid formed by soap in hard water.
2. Detergents lather even in hard water.

Answer: (b) Potassium chloride

Explanation:
1. Potassium is supplied by a potassium compound.
2. Potassium chloride contains potassium; the others supply phosphorus, calcium and nitrogen.
3. The answer is potassium chloride.

Teacher's Note:
1. Check the name of each fertilizer for potassium.
2. Potash fertilizers contain potassium.

Answer: (c) Re-crystallization

Explanation:
1. Crude salt is dissolved in water, filtered and the solution is concentrated and cooled so that pure crystals form again.
2. This process of obtaining pure crystals is re-crystallization.

Teacher's Note:
1. Pure crystals from an impure solid mean re-crystallization.
2. Evaporation alone would leave the impurities behind with the salt.

Answer: (b) (i) → (E); (ii) → (A); (iii) → (B); (iv) → (C)

Explanation:
1. Hydrochloric acid cleans bathrooms: (i) → (E).
2. Hydrated copper sulphate (blue vitriol) is sprayed on grape vines: (ii) → (A).
3. Limestone is used for flooring, statues and monuments: (iii) → (B).
4. Zincite (zinc oxide ore) is used for making paints: (iv) → (C).
5. This is option (b).

Teacher's Note:
1. Blue vitriol and vines is a famous pair (Bordeaux mixture).
2. Zinc oxide is a white pigment.

Answer: (b) Terylene

Explanation:
1. Plastics that soften on heating and harden on cooling again are thermoplastics and can be reused.
2. Melamine, bakelite and urea formaldehyde are thermosetting plastics, which set permanently once heated and cannot be remelted.
3. Terylene is a thermoplastic, so the answer is Terylene.

Teacher's Note:
1. Thermoplastic means it can be re-melted.
2. Bakelite is the best-known thermosetting plastic.

Answer: (b) blowing

Explanation:
1. Molten glass is shaped by blowing air through a tube into it, which is how laboratory glassware is made.
2. The technique is blowing.

Teacher's Note:
1. Glass-blowers shape molten glass with air.
2. Annealing means slow cooling to remove stress.

Answer: (c) proteins

Explanation:
1. Proteins contain C, H, O and N, and often P and S too.
2. They build and repair body cells.
3. The answer is proteins.

Teacher's Note:
1. Nitrogen in the list points to proteins.
2. Fats and carbohydrates contain only C, H and O.

Answer: (a) Vegetable oil

Explanation:
1. Fats give about 9 kcal per gram, while carbohydrates and proteins give about 4 kcal per gram.
2. Vegetable oil is a fat, so it gives the most energy.
3. The answer is vegetable oil.

Teacher's Note:
1. Compare energy per gram: fats are highest.
2. Glucose gives quick energy but not the most.

Answer: (c) RCC

Explanation:
1. Pillars carry heavy loads and need great strength.
2. RCC (concrete reinforced with steel) is the strongest of these.
3. The answer is RCC.

Teacher's Note:
1. Steel reinforcement gives extra tensile strength.
2. Mortar and pure cement are not used alone for pillars.

Answer: (c) Amyl acetate

Explanation:
1. Tetracycline and penicillin are antibiotics, and sulfadiazine is a sulpha drug.
2. Amyl acetate is an ester with a fruity smell and is used as a flavouring or solvent, not as a medicine.
3. The answer is amyl acetate.

Teacher's Note:
1. Esters are known for their pleasant smell.
2. The other three fight bacterial infection.

Answer: (d) DBECA

Explanation:
1. RCC is cement concrete strengthened with steel: (D).
2. Cement mortar is cement and sand in the ratio 1:4: (B).
3. Cement is made by heating limestone and clay and adding gypsum: (E).
4. Brick is baked clay: (C).
5. Concrete is cement, gravel and sand in the ratio 1:2:3: (A).
6. The order is D, B, E, C, A: option (d).

Teacher's Note:
1. Ratios are the clue: 1:4 is mortar and 1:2:3 is concrete.
2. Gypsum is added to cement to control setting.

Answer: (d) Magnesium

Explanation:
1. Magnesium burns with a dazzling white light, so it is used in fireworks.
2. Its alloys are light and are used in aircraft and automobile parts.
3. The answer is magnesium.

Teacher's Note:
1. Fireworks and a bright white flame point to magnesium.
2. Aluminium does not burn in this way.

Answer: (b) CEABD

Explanation:
1. Iron is the grey metal used in huge constructions: (C).
2. Carbon, as graphite, is dark grey and used in pencil leads: (E).
3. Silver compounds are light-sensitive and used in photographic films: (A).
4. Mercury is the liquid metal that forms amalgams: (B).
5. Iodine is a purple solid and its solution (tincture) is used on wounds: (D).
6. The order is C, E, A, B, D: option (b).

Teacher's Note:
1. A liquid metal is mercury, and the purple solid is iodine.
2. Graphite is an allotrope of carbon.

Answer: (b) form lather even with hard water

Explanation:
1. Soaps form scum with hard water and need more soap to make lather.
2. Detergents form lather even with hard water because their calcium and magnesium salts are soluble.
3. The answer is (b).

Teacher's Note:
1. The key advantage is working in hard water.
2. Detergents are often less biodegradable than soaps.

Answer: (c) Super phosphate of lime

Explanation:
1. Ammonium nitrate, calcium nitrate and ammonium sulphate all contain nitrogen.
2. Super phosphate of lime supplies phosphorus.
3. The answer is super phosphate of lime.

Teacher's Note:
1. Look for compounds with N: nitrate and ammonium.
2. The 'phosphate' fertilizer supplies P.

Answer: (c) re-crystallization

Explanation:
1. Cooling a hot saturated solution makes the solute come out as crystals.
2. This process is called re-crystallization.

Teacher's Note:
1. Crystals appearing on cooling suggest crystallization.
2. Evaporation removes the solvent by heating instead.

Answer: (c) (i) → (C); (ii) → (D); (iii) → (E); (iv) → (A)

Explanation:
1. Hydrochloric acid cleans the surface of metals: (i) → (C).
2. Copper sulphate pentahydrate is used as an insecticide: (ii) → (D).
3. The Taj Mahal is built of marble, which is calcium carbonate: (iii) → (E).
4. Plaster of Paris, CaSO₄·½H₂O, is used for casting toys and statues: (iv) → (A).
5. This is option (c).

Teacher's Note:
1. Plaster of Paris is CaSO₄·½H₂O.
2. Marble and limestone are both CaCO₃.

Answer: (a) Melamine

Explanation:
1. The coursebook lists thermosetting plastics such as melamine, bakelite and urea-formaldehyde for water tanks, cabinets of radio and television and unbreakable utensils.
2. Polyethylene and polystyrene are thermoplastics used for utensils, bags and packaging, and terylene is a fibre.
3. The answer is melamine.

Teacher's Note:
1. Think of hard, heat-resistant moulded articles: these are thermosetting plastics.
2. Melamine is also used for unbreakable crockery.

Answer: (d) flint glass

Explanation:
1. Flint glass contains lead oxide and has a high refractive index.
2. This makes it suitable for lenses and prisms.
3. The answer is flint glass.

Teacher's Note:
1. Optical glass needs a high refractive index.
2. Pyrex resists heat and is used for lab apparatus.

Answer: (b) Starch

Explanation:
1. Vegetable oil is a fat, and keratin and albumin are proteins.
2. Starch is a polysaccharide, which is a carbohydrate.
3. The answer is starch.

Teacher's Note:
1. Carbohydrates are sugars and starches.
2. Keratin is in hair and nails; albumin is in egg white.

Answer: (a) A solution of glucose

Explanation:
1. Glucose is a simple sugar that is absorbed directly into the blood and gives quick energy.
2. The answer is a solution of glucose.

Teacher's Note:
1. Simple sugars need no digestion.
2. Milk contains fat and protein that take time to digest.

Answer: (a) Cement mortar

Explanation:
1. Cement mortar (cement, sand and water) is spread on walls as plaster and also joins bricks.
2. Concrete and RCC are for structural members, and glass is not used.
3. The answer is cement mortar.

Teacher's Note:
1. Plaster must be a smooth paste.
2. Gravel in concrete makes it too coarse for plastering.

Answer: (d) Hg

Explanation:
1. An amalgam is an alloy of mercury with another metal.
2. Mercury is the silvery white liquid metal.
3. The answer is Hg.

Teacher's Note:
1. The word amalgam is linked to mercury.
2. Mercury is liquid at room temperature.

Answer: (d) Both (b) and (c)

Explanation:
1. Silver and gold are both used in Ayurvedic preparations (bhasmas).
2. So the answer that covers both is (d).

Teacher's Note:
1. Gold and silver are the noble metals used in these medicines.
2. Choose the option that includes both.

Answer: (b) Metals have poor tensile strength.

Explanation:
1. Metals conduct heat and electricity, make a ringing sound (sonorous), and can be beaten into sheets and drawn into wires.
2. Metals generally have high tensile strength, so the statement that they have poor tensile strength is incorrect.
3. The answer is (b).

Teacher's Note:
1. The word 'incorrect' means find the false claim.
2. Steel cables and bridges show that metals are strong.

Answer: (b) Brass

Explanation:
1. Brass is copper and zinc, bronze is copper and tin, duralumin is mostly aluminium and steel is iron and carbon.
2. The answer is brass.

Teacher's Note:
1. Remember: brass = Cu + Zn; bronze = Cu + Sn.
2. Duralumin has aluminium as its major metal.

Answer: (a) DCAB

Explanation:
1. Bronze has the most copper, about 88–90%, and brass has about 60–70%.
2. Duralumin (mostly aluminium, about 4% copper) and alloyed gold contain much less copper than brass.
3. The book places alloyed gold first, then duralumin, then brass and then bronze: D, C, A, B, which is option (a).

Teacher's Note:
1. Bronze is the most copper-rich of the four.
2. Brass is mainly copper, and the other two alloys are mainly other metals.

Answer: (b) tinning

Explanation:
1. Coating with zinc is galvanization and forming an alloy with mercury is amalgamation.
2. Coating with tin is tinning.

Teacher's Note:
1. The name of the process comes from the metal used.
2. Tinning is used for food containers.

Answer: (c) (i) → (C); (ii) → (B); (iii) → (D); (iv) → (A)

Explanation:
1. Hard glass is used for laboratory apparatus: (i) → (C).
2. Flint glass is used for lenses: (ii) → (B).
3. Pyrex glass is used for thermo flasks: (iii) → (D).
4. Safety glass is used for wind shields of automobiles: (iv) → (A).
5. This is option (c).

Teacher's Note:
1. Safety glass does not shatter into sharp pieces, so it suits car windows.
2. Flint glass is the optical glass.

Answer: (d) Bakelite

Explanation:
1. Thermosetting plastics set permanently when heated and cannot be softened again.
2. PVC, polystyrene and nylon are thermoplastics. Bakelite is thermosetting.
3. The answer is Bakelite.

Teacher's Note:
1. Bakelite is used for electrical switches and handles.
2. Thermoplastics soften again on heating.

Answer: (b) Urea

Explanation:
1. Triammonium phosphate gives nitrogen and phosphorus, and potassium nitrate gives potassium and nitrogen.
2. Superphosphate of lime gives phosphorus.
3. Urea contains only nitrogen as the nutrient, so the answer is urea.

Teacher's Note:
1. Look for the fertilizer with only one nutrient element.
2. Urea is CO(NH₂)₂.

Answer: (a) Fe + Si

Explanation:
1. The name ferrosilicon comes from ferrum (iron) and silicon.
2. It is an alloy of Fe and Si.

Teacher's Note:
1. Ferro means iron.
2. It is used in making steel.

Answer: (b) CDBA

Explanation:
1. Methane \(\ce{CH4}\) has 1 carbon atom.
2. Glucose \(\ce{C6H12O6}\) has 6.
3. Sugar (sucrose) \(\ce{C12H22O11}\) has 12.
4. Starch \(\ce{(C6H10O5)_n}\) has 6n carbon atoms, which is very many.
5. The order is C, D, B, A: option (b).

Teacher's Note:
1. Starch is a polymer of glucose units.
2. Sugar here means sucrose.

Answer: (c) Keratin

Explanation:
1. Glucose, starch and sucrose are carbohydrates.
2. Keratin, found in hair and nails, is a protein.
3. The answer is keratin.

Teacher's Note:
1. Hair, nails and horn are made of keratin.
2. Carbohydrate names often end in -ose.

Answer: (a) \(\ce{CO2}\)

Explanation:
1. Carbon dioxide dissolves in water under pressure to give soda water.
2. The gas is CO₂.

Teacher's Note:
1. The fizz in soda is carbon dioxide.
2. Carbonic acid is formed in small amounts.

Answer: (c) Mg

Explanation:
1. Magnesium burns with a bright white flame.
2. A magnesium ribbon is used as the fuse to start the thermite reaction.
3. The answer is Mg.

Teacher's Note:
1. Magnesium ribbon is easy to light and burns very hot.
2. It supplies the starting heat for thermite.