HSC EV Chemistry 1st Paper Question 2017 Sylhet Board

HSC EV Chemistry 1st Paper Question 2017 Sylhet Board. Chemistry Suggestion and Question Patterns of HSC Examination 2017. Chemistry, a branch of physical science, is the study of the composition, properties, and behavior of matter. Chemistry is concerned with the atoms and their interactions with other atoms, and in particular with the properties of the chemical bonds. The chemistry is also concerned with the interactions between the atoms (or groups of atoms) and various forms of energy (e.g., photochemical reactions, changes of phases of matter, the separation of mixtures of polymers, properties, etc)

HSC EV Chemistry 1st Paper Question 2017 Sylhet Board

Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules, and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances. Chemistry is the study of matter, its properties, how and why substances combine or separate to form other substances, and how substances interact with energy. Many people think of chemists as being white-coated scientists mixing strange liquids in a laboratory, but the truth is we are all chemists.

The current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, atoms, molecules, substances, metals, crystals and other aggregates of matter. This matter can be studied in solid, liquid, or gas states, in isolation or in combination. The interactions, reactions, and transformations that are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. Such behaviors are studied in a chemistry laboratory.

A chemical reaction is a transformation of some substances into one or more different substances. The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which usually involves atoms as subjects.

The number of atoms on the left and the right in the equation for a chemical transformation is equal. (When the number of atoms on either side is unequal, the transformation is referred to as a nuclear reaction or radioactive decay.) The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws. 

Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; some of them are Matter, Element, Compound, Molecule etc.

A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, it’s potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs.

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