General Science (CTET)

Biochemical oxygen demand is more in polluted water and less in potable water. A low BOD is an indicator of good quality water, while a high BOD indicates polluted water. There are generally no standards for an absolute BOD value of drinking water. However, a sample with a BOD between 1 and 2 mg/L indicates a very clean water.

Detergents are made from sodium hydroxide and fatty acids.
Sodium hydroxide is a strong base in nature and fatty acids are weak acidic in nature.

Chemists are concerned with both physical and chemical change, and the energy associated with each. Chemical reactions involve the making and breaking of covalent bonds and these transformations have energy consequences.The sum of all the bond energies of a molecule can therefore be considered its atomization energy, i.e. the energy required to break the molecule completely into its component atoms.

All the above are the correct answers.

An alloy of mercury with another metal (usually silver) used by dentists to fill cavities in teeth. Except for iron and platinum, all metals dissolve in mercury and chemists refer to the resulting mercury mixtures as amalgams.

Due to insufficient combustions of fuel, steel utensils turn black from the bottom.

This is the correct answer as one piece of magnet will have 2 poles and broken four pieces will have 8 poles.

The pH 1 represents strong acid.  Low pH values are acidic, higher values are basic.

Yes, it is correct as acceleration is directly proportional to the displacement from the mean position and directed opposite to it.
a=-(ω^2)x

Kinetic energy is the one half the mass multiplied by the square of the velocity, K=1/2mv2. If mass gets doubled, the kinetic energy also doubles.

Potassium chlorate is a compound containing potassium, chlorine, and oxygen, with the chemical formula KClO3. In pure form, it is a white crystalline substance. It is the most common chlorate in industrial use, and is usually present in well-stocked laboratories. It is used as an oxidizing agent to prepare oxygen as a disinfectant, in safety matches, and in explosives and fireworks. Potassium chlorate ( KCLO3 ) decomposes upon heating to yield potassium chloride and oxygen gas. Manganese dioxide ( MnO2 ) is mixed with potassium chlorate and behaves as a catalyst for this reaction .
2 KClO³ ---( Heat with MnO2 Catalyst )----> 2 KCl + 3 O^2_.

An orange does not  float in fresh water but since salt water is more dense than fresh water, it has a better chance of floating in the salty water. The greater buoyant force allows the orange to float in the salt water, if salty enough.

A thin layer of oil on water is called oil slick. Oil slicks float on oceans and seas, covering them in a thick film of crude or refined petroleum oil. When freight ships carrying tens of thousands of tons of fuel crash, malfunction, or encounter harsh weather, they spill enormous amounts of oil into the water.

Blue vitriol, DDT, BHC and potassium nitrate, none of these are common used pesticides. Pesticides are substances or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. Pesticides are a special kind of products for crop protection. Some common pesticides are glyphosates, atrazine, metolachlor, etc.

Chlorofluorocarbons (CFCs) are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine.
Chlorofluorocarbons released from the surface of the Earth, rise slowly into the stratosphere.This is the gas responsible for depletion of ozone layer.

Total coliforms are a group of bacteria commonly found in the environment, for example in soil or vegetation as well as the intestines of mammals, including humans. Total coliform bacteria are not likely to cause illness, but their presence indicates that your water supply may be vulnerable to contamination by more harmful microorganisms present through animal or human waste.

Wet scrubbers are the most widely FGD technology for SO² control throughout the world. Calcium, sodium, and ammonia based absorbents have been used in a slurry.
Wet scrubbers can achieve removal efficiency as high as 99%.

Birds do not have diaphragm but bats do have diaphragm.

Grafting and budding are methods of asexual plant propagation that join plant parts, so they will grow as one plant. These techniques are used to propagate cultivars that will not root well as cuttings or whose own root systems are inadequate. One or more new cultivars can be added to existing fruit and nut trees by grafting or budding.  The portion of the cultivar that is to be propagated is called the scion. It consists of a piece of shoot with dormant buds that will produce the stem and branches. The rootstock, or stock, provides the new plant’s root system and sometimes the lower part of the stem. The cambium is a layer of cells located between the wood and bark of a stem from which new bark and wood cells originate.

Laterite soils are found in tropical region with wet and dry climate these area receives seasonal heavy rainfall. Heavy rainfall leaching of soil where lime and silica leached away,  and soil is rich in oxide alluminium predominate and abundance laterite is called bauxite. Due to presence of iron oxides the colour of laterite soil is basically red. Soil is poor in lime content,  and hence it is acidic. Laterite soil are found in high level platue and hilly area that receives heavy rainfall and are specifically well developed in Eastern Ghats of Orissa,  and also in southern region of  Western Ghats.

An aerosol is a suspension of particles within a gas. Examples are clouds, and air pollution such as smog and smoke.

The Antarctic Ozone Hole was discovered by the British Antarctic Survey from data obtained with a ground-based instrument from a measuring station at Halley Bay, Antarctica, in the 1981-1983 period. They reported the October ozone loss in 1985.

Burning is the opposite reaction to photosynthesis. Burning requires oxygen and releases the water and carbon dioxide.

Convex lens are lenses that have a minimum of one surface that bends outwards and makes light to move inwards, causing the rays of light to come to a focus. A convex lens is bigger at its center in comparison to its edges and is applied in correcting long-sightedness. They are commonly used to examine small objects.

Graphite is one of the most common allotropes of carbon. Unlike diamond, graphite is an electrical conductor and can be used, for instance as the material in the electrodes of an electrical arc lamp. Graphite holds the distinction of being the most stable form of carbon under standard conditions. Therefore  it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds.
Pencil cores are called lead, even though they do not  contain lead,  they are typically made of graphite.

Day and night is caused by the rotation of the Earth about its axis. At any given time, the half facing the Sun will be shined upon while the other half will have no light. Places in the former will therefore experience day while places in the latter will experience night.

Tube within tube is a type of body plan in animals. The organism has two openings, one for food and one for the elimination of waste, it has  a specialized digestive system.

Most types of bacteria survive freezing, but they do become inactive while the food is slowly and safely  preserved preferably overnight in the refrigerator.

45 dB intensity of sound regarded as the safe noise level for the city.

Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Solid particles entered by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans. 

Biosphere Reserves are sites for experimenting with and learning about sustainable development.
There are three main parts to a reserve. The first part is called the core zone, which is strongly protected for the conservation of biological diversity to make sure that different types of plants and animals are safe from human impact. The second part is called a buffer zone and surrounds the core zones and provide a space for environmental research, recreation, and tourism. The last part is called a transition zone  and this area is for local communities that have  hand in managing the resources of the area through farming, fisheries, and other non-governmental activities. Ultimately, the ways that these three zones operate depend on the specific needs of the biosphere reserve they are in.

For a given pressure, there is a temperature above which liquid cannot exist in liquid form. This temperature is called boiling point. At this pressure and at this temperature, if liquid is heated up, the temperature will not rise and heat is used only to convert the liquid into its vapour. The process of conversion of liquid into its vapour at this temperature is called boiling. Depending upon the pressure, there are many boiling temperature for a liquid. If the pressure is lowered the boiling temperature is lowered. For a given pressure, if the temperature of the liquid is below its boiling point, still the liquid is converted into vapour by the surface of the liquid. This process is called evaporation. Evaporation can take place at any temperature below the boiling temperature where as boiling can take place only at boiling temperature.