The Jan12th Static Quiz on Science and Technology (Physics, Chemistry, Bio-Chemistry, Bio-Technology)

Ans;- b) Only 2 and 3

Explanation;-

• As question is asked to choose incorrect the 2nd and 3rd statement is incorrect because thorium can generate more energy compared to natural Uranium that’s y 2nd statement is incorrect.
• The 3rd statement is incorrect because Thorium produces less harmful compared to Uranium.

About Thorium and Reserves in India

• Thorium is a chemical element with symbol Th and atomic number 90.
• It is one of only two significantly radioactive elements that still occur naturally in large quantities [other being uranium]. Thorium metal is silvery and tarnishes black when exposed to air.
• Thorium is weakly radioactive: all its known isotopes are unstable, with the seven naturally occurring ones (thorium-227, 228, 229, 230, 231, 232, and 234).
• Thorium-232 is the most stable isotope of thorium and accounts for nearly all natural thorium, with the other five natural isotopes occurring only in traces.

• Thorium is estimated to be about three to four times more abundant than uranium in the Earth’s crust, and is chiefly refined from monazite sands [Monazite contains 2.5% thorium][Monazite is a widely scattered on the Kerala Coast].
• Thorium is predicted to be able to replace uranium as nuclear fuel in nuclear reactors, but only a few thorium reactors have yet been completed.

Ans;- a) Slow down the speed of neutrons

Explanation;-

• The function of heavy water in a nuclear reactor is to slowing down the speed of neutrons.
• Heavy water is used in certain types of nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238, which captures neutrons without fissioning.
• Water cooled nuclear reactors slow neutrons down to “thermal” speed to increase the probability of their interactions with other nuclei.

About Heavy Water

• Water containing significantly more than the natural proportions (one in 6,500) of heavy hydrogen (deuterium, D) atoms to ordinary hydrogen atoms. 
• Heavy water is used as a moderator in some reactors because it slows down neutrons effectively and also has a low probability of absorption of neutrons.
• Heavy water is one of the two moderators that can be used which allow a nuclear reactor to operate using natural uranium. The other moderator is graphite.
• The heavy water is kept under pressure which increases its boiling point so that it can operate at high temperatures without boiling.
• In the laboratory heavy water is employed as an isotopic tracer in studies of chemical and biochemical processes.
• The heavy water is not manufactured, but rather it is extracted from the quantity that is found naturally in lake water. The water is separated through a series of towers, using hydrogen sulphide as an agent. Owing to AECLs CANDU programme, Canada is the world’s supplier of heavy water.

Ans;- c) The density of water is maximum at 4°C

Explanation;-

• When it is cooled from the room temperature, the liquid water tends to become increasingly dense, as with another kind of substances, but approximately at about 4°C, pure water is said to reach its maximum density. As it gets cooled further, it tends to expand and becomes less dense.
• Water density at 4 degree Celsius is more than the density of water at 0 degree Celsius.
• Water is bad conductor of heat. At water level of we start to heat the water surface then heat will not travel to bottom. But if we start to heat water from bottom the heat will reach top level only because and by the convection that happens.
• Due to the density difference the water at 0 degree Celsius will rise up to top level as it is lighter than the water at 4 degree Celsius.
• Heat from the outer atmosphere will not in or heat from the bottom of the ice will not travel out.
• And hence heat is restricted inside or bottom side of ice which will help water to be in liquid state.
• This is how the water below the ice will remain at that same temperature in liquid state.

Ans;- c) most of the root hairs are lost during  transplantation

Explanation;-

• During a transplant the fine roots are destroyed due to the jostling during the uprooting process.
• These root hairs come under a shock.
• The plant which has been transplanted either takes time to readjust to the new soil or dries up and dies due to the root hair loss.

Ans;- a) Only 1 and 2

Explanation;-

As question asked to choose incorrect the 1st and 2nd are not examples of chemical change

• The crystallization of sodium chloride is physical change and no chemical change takes place.

• Melting of ice is also physical change.
• It changes into other physical form i.e. water.
• Souring of milk is a chemical change as bacteria activates the formation of lactic acid which turns milk sour.

Ans;- c) rate of respiration is decreased

Explanation;-

• Fruits and vegetables continue their metabolic activity after harvest.
• Metabolic Activity is manifested by respiration. Reduction of temperature is an effective means of reducing the rate of respiration.

Ans;- d) All of the above

Explanation;-

• All the things can be transferred by Recombinant DNA Technology

• Recombinant DNA Technology is defined by the Encyclopedia Britannica as “the joining together of DNA molecules from different organisms and inserting it into a host organism to produce new genetic combinations that are of value to science, medicine, agriculture and industry.”

Ans;- d) All of the above

Explanation;-

• Mycorrhiza are symbiotic associations between plant roots and certain soil fungi which play a key role in nutrient cycling in the ecosystem and also protect plants against environmental and cultural stress.
• mycorrhizae) permits the plant to obtain additional moisture and nutrients. This is particularly important in uptake of phosphorus, one of the major nutrients required by plants. When mycorrhizae are present, plants are less susceptible to water stress.
• Mycorrhizal associations play vital role in plant nutrition.
They greatly increase the efficiency of nutrient and water uptake enhance resistance to pathogens and buffer plant species against several environmental stresses and drought resistance.
• Mycorrhizal also improve plant growth and survival in soils contaminated by heavy metals.

Ans;- a) 1 and 2

Explanation;-

• The fourth statement seems correct but is not.
• The supernova explosions have helped astronomers determine both the distance of the galaxy and the redshift of the galaxy. The astronomers could then compare distance to expansion, and create a kind of ‘expansion history’ of the Universe.
• This showed that the expansion of universe was “increasing” means “the Universe’s expansion is accelerating”.
• ‘Red shift’ is a key concept for astronomers. The term can be understood literally – the wavelength of the light is stretched, so the light is seen as ‘shifted’ towards the red part of the spectrum. Something similar happens to sound waves when a source of sound moves relative to an observer.

Ans;- a) To make it pest-resistant

Explanation;-

• Bt Brinjal is a genetically modified (GM) crop created by inserting Cry 1Ac gene from the soil bacterium Bacillus thuringiensis into Brinjal.
• The insertion of the gene gives Brinjal plant resistance against lepidopteron pets/insects like the Brinjal Fruit and Shoot Borer (Leucinodes orbonalis) and Fruit Borer (Helicoverpa armigera).