Basic Concept of Chemistry - Chemistry

Topics: Thermodynamics
Subject: Chemistry

Topics: Basic Concept of Chemistry

Subject Code: CHM 4201

Lecturer: Mr. Jahedul Islam  

Lecture No- 1 and 2

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Basic Concept of Chemistry

Chemistry is a branch of physical science that studies the composition, structure, properties and changes of matter through reactions.

It deals with the interactions of substances through inter molecular forces.

Chemistry also includes the properties of individual atoms, how atoms form chemical bonds to create chemical compounds.

And the interactions between substances through chemical reactions to form different substances

Chemicals

ÒChemical Substances or Chemicals are form of matter that has constant chemical composition and characteristic properties.

ÒIt cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds.

ÒChemical substances can be chemical elements, chemical compounds, ions or alloys.

ÒChemical substances exist as solids, liquids, gases, crystals or colloids  etc.

ÒExamples ?  Say yourself !!!!!!!!

Parts of Chemistry

Organic Chemistry

Inorganic Chemistry

Physical Chemistry

Another two parts of chemistry are,

ØAnalytical 

ØChemistry

ØBiochemistry

Organic Chemistry

Organic chemistry – Study of the structure, properties, composition, mechanisms and reactions of organic compounds that contain carbon

Or simply, the study of chemicals that contain carbon.

    Examples – Chemicals in living organisms,

  - Hydrocarbons

Inorganic chemistry deals with the properties, functions, synthesis and behavior of inorganic compounds

Or simply, the study of chemicals that do not contain carbon.

ÒExamples – NaOH, KCl etc.

Say yourself

ÒSulfuric Acid                           H2SO4

ÒMethane                                 CH4

ÒSodium Chloride                     NaCl

ÒGlucose                                   C6H12O6

ÒHydrochloric Acid                    HCl 

ÒEthane                                     C2H6

ÒCopper-sulfate                       CuSO4

Physical Chemistry

ÒPhysical chemistry – study of the physical and fundamental basis of chemical systems and processes. Or,

ÒThe study of :

ÉThe mechanism

ÉThe rate

ÉThe energy transfer

ÉThermodynamics

ÉChemical equilibrium etc. 

with the concept of physics, e.g., motion, force, energy, time etc. that happens when matter undergoes change.

Biochemistry

ÒStudy of processes that take place in organisms.

ÒChemistry of living organisms.

ÒExamples: Animals, Plants, Microorganisms etc.

Atoms

ÒAn atom is the smallest particle or, constituent unit of ordinary matter that has the properties of a chemical element.

ÒEvery solid, liquid, gas is composed of neutral or ionized atoms.

ÒAtoms are very small; typical sizes are around 100 picometers (a ten-billionth of a meter)

Structure of Atom

ÒThe atom is composed of various subatomic particles.

The constituent particles of an atom are the electron, the proton and the neutron

Chemical Bonds ?

ÒIonic bonds: Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions.

ÒThe ions are atoms that have gained one or more electrons (known as anions)

ÒAnd atoms that have lost one or more electrons (known as cations).

Ø Covalent bonds: A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms.

Ø These electron pairs are known as shared pairs or bonding pairs or lone pairs. 

Hydrogen bonds: A hydrogen bond is the electrostatic attraction between two polar groups that occurs when a hydrogen (H) atom covalently bound to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F).

Molecule

ÒA molecule is an electrically neutral group of two or more atoms held together by chemical bonds.

ÒH2 Molecule →     H••H → H-H

ÒH2O Molecule → H••O••H → H-O-H

ÒCO2 Molecule → O : C : O → O-C-O

Elements

ÒA chemical element is a species of atoms having the same number of protons in their atomic nuclei.

ÒAll atoms of an element are same.

ÒThere are 118 elements that have been identified,

ÒFirst 94 occur naturally on Earth with the remaining 24 being synthetic elements.

Periodic Table Chart 

Compounds

ÒA chemical compound is consisting of two or more atoms, at least two from different elements, which associate via chemical bonds.

ÒThere are few types of compounds, depending on bonds:

ØCovalent compounds: held together by covalent bonds,

ØIonic compounds: held together by ionic bonds,

ØIntermetallic compounds: held together by metallic bonds.

Intermolecular Forces

ÒInter-molecular forces (IMFs) are the forces which mediate interaction between molecules, including forces of attraction or repulsion which act between molecules and other types of neighboring particles, e.g., atoms or ions.

ÒSame charged particle repulsion, opposite charged particle attraction.

Solutes, Solvents & Solutions

•A homogeneous mixture, such as a glass of tea, is called a solution.

•Aqueous solutions are solutions in which water is the solvent.

Solutes, Solvents & Solutions

•Solute is the substance present in the smallest amount.

•Solvent is the substance present in the greatest amount.

•When sugar is added to a glass of water, sugar is the solute and water is the solvent.

PH Concept

•The formal definition of pH is the negative logarithm of the hydrogen ion concentration or activity of a particular solution.

•pH = -log[H+]

•pH is a unit of measure which describes the degree of acidity or alkalinity (basic) of a solution.

•It is measured on a scale of 0 to 14.

PH Concept

ÒThe pH value of a substance is directly related to the ratio of the hydrogen ion and hydroxyl ion concentrations.

ÒIf the H+ concentration is higher than OH- the material is acidic.

ÒIf the OH- concentration is higher than H+ the material is basic.

Ò7 is neutral, < is acidic, >7 is basic

Acids and bases

• The pH is a measure of how acidic (H+) or   basic (-OH) a solution is.

• A scale with values ranging from below 0 to   above 14 is used to measure pH.

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