Chemistry MCQs for DSSSB TGT/PGT/PRT Exam

Hydrogen bonding is a type of attractive force that occurs between molecules when a hydrogen atom is covalently bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine. In water molecules, hydrogen bonding occurs between the positively charged hydrogen atoms of one water molecule and the negatively charged oxygen atoms of another water molecule. These hydrogen bonds cause the water molecules to attract each other and stick together, which gives water many of its unique properties, such as its high surface tension and its ability to act as a solvent. The hydrogen bonds do not cause the water molecules to repel each other or to compactly arrange, but they do make it more difficult for the molecules to slide over each other, which contributes to the high viscosity of water.

In molecular physics, the van der Waals forces, named after Dutch scientist Johannes Diderik van der Waals, are distance-dependent interactions between atoms or molecules. Unlike ionic or covalent bonds, these attractions are not a result of any chemical electronic bond, and they are comparatively weak and more susceptible to being perturbed. Van der Waals forces quickly vanish at longer distances between interacting molecules.

Van der Waals forces play a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. Van der Waals forces also define many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media.

Phalcon is radar system provided by Israel to India.

Chemical bonding forces are not considered to be part of van der Waals forces. Van der Waals forces include London forces, dipole-dipole forces, and dipole-induced dipole forces.

 

One end of a match is coated with a material that can be ignited by frictional heat generated by striking the match against a suitable surface. The coated end of a match, known as the match "head," contains either phosphorus or phosphorus sesquisulfide as the active ingredient and gelatin as a binder.

Diamond is harder than graphite because diamond has a more complex structure. Diamond's structure is like many pentagons connected together, each pentagon sharing a side with another pentagon or each pentagon sharing a point with another pentagon. All the points are linked together in some way. Graphite's structure is very loose, with its bonds forming layers.

Dipole-dipole interaction energy between stationary polar molecules is proportional to 1/ r³ and that between rotating polar molecules is proportional to 1/ r⁶ where ‘r’ is the distance between polar molecules

Besides dipole - dipole interaction, polar molecules can interact by London forces also.

Thermal energy is the energy of a body arising from motion of its atoms or molecules. It is directly proportional to the temperature of the substance. It is the measure of average kinetic energy of the particles of the matter and is thus responsible for movement of particles. This movement of particles is called thermal motion. We have already learnt that intermolecular forces tend to keep the molecules together but thermal energy of the molecules tends to keep them apart. Three states of matter are the result of balance between intermolecular forces and the thermal energy of the molecules.

Param Padma, a supercomputer was introduced in April 2003. It had a peak speed of 1024 GFLOPS (about 1 TFLOP) and a peak storage of 1 TB.

Idukki district of Kerala has become first district in India to have high speed Rural Broadband Network i.e. National Optical Fibre Network (NOFN) Internet connectivity. NOFN is the largest rural connectivity project of its kind in the world.

The asteroid belt is a doughnut-shaped concentration of many different sized asteroids between the orbits of Mars and Jupiter, closer to the orbit of Mars. The asteroids orbit the Sun. The asteroid belt is not smooth but there are concentric gaps in it known as Kirkwood gaps.

Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2. 1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten.

A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig bladder. Some balloons are used for decorative purposes, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation.