General Science Previous Year Questions (PYQ) with Answers – Page 35

A single compound, silver chloride, breaks down into two simpler substances, silver and chlorine, which is exactly what a decomposition reaction is.

Most carbon compounds are poor conductors of electricity, because their atoms are joined by covalent bonds and they do not form ions or free electrons that could carry a current.

Urea, CO(NH₂)₂, contains carbon, oxygen, nitrogen and hydrogen; it has no phosphorus at all and is a nitrogenous fertilizer. Urea carries about 46% nitrogen, the highest of the common solid fertilizers, which is why it is the most widely used fertilizer in India.

Diamond and crystalline silicon have the same crystal structure. Isomorphous means having the same crystal form.

This is a hydrolysis reaction in which no element changes its oxidation number, so nothing is oxidised or reduced. A redox reaction is one in which one substance loses electrons (its oxidation number rises) and another gains them (its oxidation number falls).

The element with atomic number 35 is bromine, whose 35 electrons are arranged as 2, 8, 18, 7, leaving seven in the outermost shell.

Potential energy is the energy a body stores because of its position or because its shape has been changed. A body raised to a height h has gravitational potential energy equal to mgh, where m is its mass and g is the acceleration due to gravity.

By the law of conservation of momentum, the boy and the cart move together with the momentum the boy brought, so their speed is 104 ÷ 55, about 1.89 m/s. With frictionless wheels, no outside horizontal force acts, so total momentum stays the same.

Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen. Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria.

A lever is a rigid bar turning about a fulcrum, and by the principle of moments the load multiplied by the load arm equals the effort multiplied by the effort arm, so a long effort arm lets a small effort balance a large load; this is the simplest way of…

By Newton's second law, F = m × a, so a = F ÷ m = 5 N ÷ 10 kg = 0.5 m/s².

In the cytoplasm, glucose is split by glycolysis into two molecules of pyruvate, releasing a small amount of energy as ATP.

When the force acts opposite to the displacement, the angle between them is 180°, and work W = F d cos 180° = −F d. Work done by a force is the product of the force, the displacement and the cosine of the angle between them.

Lymph forms when plasma leaks out of blood capillaries into the spaces between cells, so it is essentially plasma with less protein and no red blood cells.

PET fibre (polyester) is blended with wool and cotton, and PET bottles are widely recycled into new products. Polyethylene terephthalate is a polyester made from ethylene glycol and terephthalic acid.

Typhoid is caused by the bacterium Salmonella typhi; the other three are viral diseases. Salmonella typhi spreads through food and water contaminated with the faeces of an infected person, which is why typhoid is common where sanitation is poor.

Every living cell needs a cell membrane, and plant cells add a rigid cell wall outside it. The cell membrane, or plasma membrane, is the thin, selectively permeable boundary of every cell; it controls what enters and leaves.

The dogfish is a small shark, and sharks are true fishes of the class Pisces. Pisces are aquatic vertebrates that breathe through gills, swim with fins and usually have scales.

Bile breaks fat into tiny droplets and lipase then splits those droplets into fatty acids and glycerol. Bile is made by the liver, stored in the gall bladder and poured into the duodenum.

Yeast is a single-celled fungus, placed in kingdom Fungi in Whittaker's five-kingdom system. Yeast cells are eukaryotic, have a cell wall containing chitin and do not make their own food, which are the marks of fungi.