General Science GK Questions with Answers – Page 44

In photosynthesis, the oxygen released into the air comes from water molecules that are split using light energy. Photosynthesis takes place in the chloroplasts of green plants.

Pure iron melts at about 1,538°C, so 1,500°C is the only option close to its melting point. Iron is a metal with strong metallic bonds, so a great deal of heat is needed to break up its solid structure.

Blood is a fluid connective tissue, with cells floating in a liquid matrix called plasma. Connective tissues link and support other parts of the body, and they have cells spread out in a matrix.

Current multiplied by resistance gives voltage, by Ohm's law, not electrical power. Electrical power is the rate at which electrical energy is used, and its basic formula is P = VI, where V is the potential difference and I is the current.

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.

DNA copies itself from loosened chromatin, and chromatin condenses into chromosomes before division, but prokaryotes divide differently from eukaryotes. In a non-dividing eukaryotic cell, DNA lies in the nucleus as a loose network called chromatin.

Bronchioles are the fine branches of the airways in the lungs, and their walls have no cartilage. Cartilage is a firm but flexible connective tissue.

This is wrong, because a compound is a pure substance with a fixed composition throughout. Pure substances are of two kinds, elements and compounds.

Zinc gives hydrogen with both acids and alkalis, and it displaces copper from copper sulphate, but statement III mixes up the acids of tamarind and tomato.

Dengue is known for lowering the platelet count, which can lead to bleeding in severe cases. Dengue is a viral disease spread by the bite of the Aedes mosquito, mainly Aedes aegypti, which breeds in clean, stagnant water and bites during the day.

This is false, because most antibiotics, starting with penicillin, come from microbes. Alexander Fleming discovered penicillin in 1928 from the mould Penicillium notatum, which stopped the growth of bacteria around it.

Oxygen-rich blood from the lungs returns through the pulmonary veins into the left auricle (left atrium) of the heart. The human heart has four chambers: two upper auricles (atria) that receive blood and two lower ventricles that pump it out.

Sound travels through water at about 1,480 metres per second at 20°C, which rounds to 1,500 m/s. Sound is a mechanical wave and needs a medium.

Osmosis is the movement of water from a dilute solution to a more concentrated one across a selectively permeable membrane.

Charge equals current multiplied by time, and 1.0 A for 600 seconds gives 600 coulombs. Electric current is the rate of flow of charge, so I = Q ÷ t, or Q = I × t. Time must be in seconds: 10 minutes is 10 × 60 = 600 seconds.

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.

A balanced diet contains all the nutrients the body needs, along with roughage and water, in the right amounts. Carbohydrates and fats give energy, proteins build and repair the body, and vitamins and minerals protect against disease and keep body processes running.

Four grams of hydrogen gas is two moles, so it contains 2 × 6.022 × 10²³, about 1.2 × 10²⁴ molecules, not 6.022 × 10²³.

The total mass of the reactants equals the total mass of the products, which is exactly what this law states.

More base than acid has been added, so the mixture is basic, and phenolphthalein turns pink in a basic solution.