Day 24: Static Quiz on Science

Correct Answer: B
Answer Justification : Justification: A thermoset is a material (such as rubber) that cures or hardens into a given shape, generally
through the application of heat. Curing is an irreversible chemical reaction in which permanent connections (known as cross- links) are
made between the material’s molecular chains. These cross-links give the cured polymer a three-dimensional structure, as well as a higher degree of rigidity than it possessed prior to curing. A cured thermoset material will not remelt or otherwise regain the processibility it had before being cured. Curing changes the material forever. Thermoset polymers outperform thermoplastics in a number of areas, including mechanical properties, chemical resistance, thermal stability, and overall durability. For these reasons, thermoset parts tend to make more effective seals. A thermoplastic material softens (becomes pliable and plastic) when heated, but it does not cure or set. A thermoplastic often begins in pellet form, then becomes softer and more fluid as heat increases. This fluidity allows it to be injected under pressure from a heated cavity into a cool mold. As it cools, the thermoplastic will harden in the shape of the mold, but there is no chemical curing at work. No cross-links are formed as with a thermoset material. The changes seen in the thermoplastic are purely physical and, with the reapplication of heat, wholly reversible.

Correct Answer: C
Answer Justification: Explanation & Learning: If electrical equipment is on fire, water may conduct electricity and harm those trying to douse the fire. Water is also not suitable for fires involving oil and petrol. So, it sinks below the oil, and oil keeps burning on top.
On the other hand, CO2, being heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled. The added advantage of CO2 is that in most cases it does not harm the electrical equipment.

Correct Answer : C
Answer Justification :
Justification: In the most common type of flame, hydrocarbon flames, the most important factor determining color is oxygen supply and the extent of fuel-oxygen pre-mixing, which determines the rate of combustion and thus the temperature and reaction paths, thereby producing different color hues. Different flame types of a Bunsen burner depend on oxygen supply. In the diagram above, on the left a rich fuel with no premixed oxygen produces a yellow sooty diffusion flame; but on the right a lean fully oxygen premixed flame produces no soot and the flame color blue. The same thing happens in a candle and a stove.

Correct Answer : B
Answer Justification :
Learning: In the present day, imitation silk may be made with rayon, mercerized cotton, polyester, a blend of these materials, or a blend of rayon and silk. Rayon is a manufactured fiber made from regenerated cellulose fiber. The many types and grades of rayon can imitate the feel and texture of natural fibers such as silk, wool, cotton, and linen. The types that resemble silk are often called artificial silk.
Rayon is made from purified cellulose, primarily from wood pulp.

Correct Answer : D
Answer Justification :
Justification: Statement 1: Due to the immobilization of phosphate by mineral ions such as Fe, Al and Ca or organic acids, the rate of available phosphate (Pi) in soil is well below plant needs. Hence, the need for such biofertilizers.
Statement 2: Blue-green algae belonging to a general cyanobacteria genus fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and lowland conditions.
Statement 3: Rhizobiuminoculant is used for leguminous crops. Azotobacter can be used with crops like wheat, maize, mustard, cotton, potato, and other vegetable crops. Azospirillum inoculations are recommended mainly for sorghum, millets, maize, sugarcane, and wheat. Nitrogen-fixation by cyanobacteria such as (Anabaena, a symbiont of the aquatic fern Azolla), provides rice plantations with biofertilizer. Free-living cyanobacteria are also present in the water column in rice paddies.

Correct Answer: A
Answer Justification :
Justification: Statement 1: Formation of ozone consumes oxygen.
Statement 2: If you notice, the only major process returning oxygen is photosynthesis. This is why afforestation can tackle climate change and pollution.
Statement 3: The process of nitrogen-fixing by bacteria does not take place in the presence of oxygen.

Correct Answer: B
Answer Justification :
Learning: IUPAC (International Union of Pure and Applied Chemistry) name for the chemical is Ethanethiol. An alternate name for the substance is Ethyl Mercaptan. It is a colorless gas or clear liquid with a distinct odor. Ethanethiol is toxic. It occurs naturally as a minor component of petroleum and may be added to otherwise odorless gaseous products such as liquefied petroleum gas (LPG) to help warn of gas leaks. At these concentrations, ethanethiol is not harmful.

Correct Answer : D
Answer Justification :
Justification: Statement 1: Liquid nitrogen, which has a boiling point of -195.8 degree Celsius is used by molecular gastronomy chefs to instantly freeze food and drinks.
Recently, it is also being popular in preparing cocktails, as it can immediately chill glasses of ingredients. It also adds a smoking effect to the drink.
It cools any substance immediately. The rapidity of cooling is also responsible for smaller ice
crystals that give a smooth texture to the ice cream.
Issues: As it evaporates, liquid nitrogen freezes everything around it, including tissues that
come in contact with it.
According to experts, food and drinks that are prepared with liquid nitrogen should be
consumed only after all the gas has bubbled off.
Statement 2: It is a colored, odorless, non-inflammable gas. It is a cryogen, which means it is used to create extremely low temperatures.
The gas is so cold that it is capable of rapid freezing any living tissue coming in contact with it.
Statement 3: Liquid nitrogen is permitted as an additive in frozen food as per the guidelines of the national regulatory body Food Safety and Standards Authority of India (FSSAI).
However, when it comes to the use of liquid nitrogen it is a grey area. There is no clear-cut guideline for it and generally, it is considered to be a novel technique, which can be used by food business operators.

Correct Answer : A
Answer Justification :
Justification: Statement 1: Descent with Modification (“Evolution”) has occurred by branching (different species share common ancestral species)
Evolution (what Darwin more descriptively called “Descent with Modification”) embodies 2 separable aspects:
 Change within a lineage
 Branching (different species share ancestors: Descent = Cladogenesis)
Branching theory says that species lineages usually change over time (though rates of change may vary) and are derived from common ancestral lineages; natural selection is the main, but not exclusive, mechanism.

Correct Answer : D
Answer Justification :
Concept and Learning: Lamarckism is the idea that an organism can pass on characteristics that it has acquired during its lifetime to its offspring (also known as heritability of acquired characteristics or soft inheritance). The environment influences all types of organisms. A change in the environment brings about changes in organisms. It gives rise to new needs. New needs or desires produce new structures and change the habits of the organisms. If an organ is constantly used it would be better developed whereas disuse of organ results in its degeneration.
Whatever an individual acquires (to possess) characters in its lifetime due to internal vital force, the effect of environment, new needs and use and disuse of organs, they are inherited (transmitted) to the next generations. The process continues. After several generations, the variations are accumulated up to such extent that they give rise to new species.