General Science Questions (MCQs) for Competitive Examinations

Notes:
Mercury belongs to the zinc group of elements in the periodic table, which comprises zinc, cadmium and mercury. They all have completely filled-up atomic orbitals. It becomes difficult to knock out these electron(s) from their orbitals and form metallic bonds. With its filled shell electron configuration it is very reluctant to form bonds even with other mercury atoms.

Notes:
The melting point of a pure substance is always higher than the melting point of that substance when a small amount of an impurity is present. Melting point decreases with increase of impurity in water. Increase in impurity increases the electrostatic attraction between ions and thus more energy is needed to break the bonds. The surface tension of water increases when highly soluble impurities are added to it.

Notes:
Plasma consists of freely moving ions and electrons. It forms when energy supplied to a gas causes ionization. Plasma is present in stars, including the Sun. It conducts electricity and responds to magnetic fields. Irving Langmuir coined the term “plasma” in 1928. Plasma is different from solids, liquids, and gases due to its unique electrical properties.

Notes:
Heavy water is water that contains heavy hydrogen or deuterium. Deuterium differs from the hydrogen usually found in water, protium, in that each atom of deuterium contains a proton and a neutron. Heavy water may be deuterium oxide, D2O or it may be deuterium protium oxide, DHO.

Notes:
The Moon has been bombarded with large quantities of Helium-3 by the solar wind. It is thought that this isotope could provide safer nuclear energy in a fusion reactor, since it is not radioactive and would not produce dangerous waste products.

Notes:

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. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another.

Notes:
Multicellular organisms are made up of more than one cell. The development of multicellular organisms is accompanied by cellular specialization and division of labor; cells become efficient in one process and are dependent upon other cells for the necessities of life. Paramecium is single-celled protists naturally found in aquatic habitats. Paramecium is the only genus in the family Parameciidae, which resides within the phylum Ciliophora.

Notes:
Trochodendron is a genus of flowering plants with one living species. It is vesselless angiosperm. Fewer than 200 species of angiosperms have the primitive feature of vesselless wood. With two exceptions— Trochodendron and Tetracentron; all vesselless angiosperms occur in the Magnolidae.

Notes:
Veins carry the deoxygenated blood from different parts of the body to the heart. There are two main veins that carry out this job. The superior vena cava carries deoxygenated blood from head, neck, thorax and hands to the right atrium of our heart. The inferior vena cava carries deoxygenated blood from legs, pelvic region and abdominal organs to the right atrium of our heart. Among the veins, only pulmonary vein carries oxygenated blood.

Notes:
The plastid is a major double-membrane organelle found in the cells of plants. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. Plastids often contain pigments used in photosynthesis, and the types of pigments present can change or determine the cell’s colour.