Toll Free 1800 572 9282   
mailus@wbcsmadeeasy.in
  
 

Recent updates

WBCS 2024 Exam is nearing. See W.B.C.S. (Exe.) Etc. Exam 2023 Notification for details syllabus age scheme qualification strategy booklist etc.


Admission to WBCS Foundation Course (Pre, Main, Interview) 2024/25 Announced for online & offline batch. Limited Seats. Join us NOW!!! Click here for details.
WBCS Foundation Course Classroom Online 2024 2025 WBCS Preliminary Exam Mock Test WBCS 2021 Group A and B Toppers
  • Home /Exam Details (QP Included) / Main Exam / Compulsory Papers / Paper IV : General Studies II / Notes On Chemistry-Metal-Non-Metal-Metalloid-Liquid-Surface tension-Viscosity-Gas Laws-Periodic Table-For WBCS Main Exam
    • Notes On Chemistry-Metal-Non-Metal-Metalloid-Liquid-Surface tension-Viscosity-Gas Laws-Periodic Table-For WBCS Main Exam
    Posted on May 2nd, 2018 in Paper IV : General Studies II
    Tags:

    Notes On Chemistry-Metal-Non-Metal-Metalloid-Liquid-Surface tension-Viscosity-Gas Laws-Periodic Table-For WBCS Main Exam

     

     

    Chemistry as a subject assumes a significant part in all competitive examination.It has a prominent role in Prelims and General studies Papers. It is an interesting subject. If aspirants are profound of this subject, no doubt you can choose this as your optional subject for W.B.C.S mains Exam. It is an endless subject .This is very easy and scoring optional if approached rightly, a correct strategy is always important.

    Metals vs. Non-metals vs. Metalloid.Continue Reading Notes On Chemistry-Metal-Non-Metal-Metalloid-Liquid-Surface tension-Viscosity-Gas Laws-Periodic Table-For WBCS Main Exam.
    Metal Non-metal
    1. Metals comprise more than 78% of all known elements
    2. They appear on the left side of the Periodic Table
    • located at the top right hand side of the Periodic Table.
    • the non- metallic character increases as one goes from left to right across the Periodic Table
    usually solids at room temperature [mercury is an exception; gallium and caesium also have very low melting points (303K and 302K, respectively)]. Non-metals are usually solids or gases at room temperature with low melting and boiling points (boron and carbon are exceptions)
    Have high melting and boiling points. –
    Good conductors of heat and electricity. poor
    malleable: can be flattened into thin sheets by hammering Brittle
    ductile: can be drawn into wires nope

    Semi-metals or Metalloids: silicon, germanium, arsenic, antimony and tellurium show properties that are characteristic of both metals and non- metals.

    Liquids: Properties

    1. Liquids have definite volume because molecules do not separate from each other.
    2. Liquids can flow, they can be poured, because their Molecules can move past one another freely.
    3. Liquids can assume the shape of the container in which these are stored.
    4. Liquids may be considered as continuation of gas phase into a region of small volume and very strong molecular attractions.
    5. Physical properties of liquid = (1) vapour pressure (2) surface tension (3) viscosity. These are due to strong intermolecular attractive forces.

    Liquids: Vapour Pressure

    • liquid evaporates and pressure exerted by vapour on the walls of the container (vapour pressure)
    • The normal boiling point of water is 100 °C (373 K), its standard boiling point is 99.6 °C (372.6 K).
    • Standard boiling point of the liquid is slightly lower than the normal boiling point because 1 bar pressure is slightly less than 1 atm pressure.
    • Liquids at high altitudes boil at lower temperatures in comparison to that at sea level, because at high altitudes atmospheric pressure is low.
    • In hills, water boils at low temperature therefore, Pressure cooker is used for cooking food.
    • In hospitals surgical instruments are sterilized in autoclaves. Autoclaves increase the boiling point of water by increasing the pressure above the atmospheric pressure by using a weight covering the vent.
    • Boiling does not occur when liquid is heated in a closed vessel.

    Liquid Surface Tension

    1. Small drops of mercury form spherical bead instead of spreading on the surface.
    2. Particles of soil at the bottom of river remain separated but they stick together when taken out.
    3. Liquid rise (or fall) in a thin capillary as soon as the capillary touches the surface of the liquid.
    4. On flat surface, droplets are slightly flattened by the effect of gravity; but in the gravity free environments, the liquid drops will be perfectly spherical.

    Viscosity & Laminar flow

    • Viscosity is a measure of resistance to flow which arises due to the internal friction between layers of fluid
    • SI unit of viscosity coefficient= 1 newton second per square metre = pascal second
    • CGS unit of viscosity coefficient = Poise (named after great scientist Jean Louise Poiseuille).
    • Greater the viscosity, the more slowly the liquid flows.
    • Viscosity of liquids decreases as the temperature rises.
    • Glass is an extremely viscous liquid- so viscous that many of its properties resemble solids.
    • Windowpanes of old buildings- they become thicker at bottom than at top. This is because of liquid flow property of glass.
    • Laminar flow is type of flow in which there is a regular gradation of velocity in passing from one layer to the next.

    Gas: Properties

    1. Gases are highly compressible
    2. Gases exert pressure equally in all directions.
    3. Gases have much lower density than the solids and liquids.
    4. Gases can assume volume and shape of the container. Their volume and the shape of gases are not fixed.
    5. Under suitable temperature and pressure conditions gases can be liquified
    6. Gases mix evenly and completely in all proportions without any mechanical aid.
    7. The noble gases exhibit very low chemical reactivity because all of their orbitals completely filled by electrons. Very difficult to add/remove electrons from it. (Example: helium, neon, argon, krypton, xenon, radon, and element 118)
    8. 11 elements exist as gases.

    Gas Laws

    Robert Boyle,Anglo-Irish
    • first reliable measurement on properties of gases (1662)
    • Boyle’s Law (Pressure – Volume Relationship)
    • at constant temperature, the pressure of a fixed amount (i.e., number of moles n) of gas varies inversely with its volume.
    • P1V1=P2V2= constant
    • Gases are highly compressible because when a given mass of a gas is compressed, the same number of molecules occupy a smaller space
    • This means that gases become denser at high pressure.
    Charles’ Law
    • Temperature – Volume Relationship
    • At constant pressure, volume of a gas increases on increasing temperature and decreases on cooling. (V = k2T )
    • This new temperature scale is called the Kelvin temperature scale or Absolute temperature scale.
    • Kelvin scale of temperature is also called Thermodynamic scale of temperature and is used in all scientific works.
    • Each line of the volume vs temperature graph is called isobar.
    • The lowest imaginary temperature at which gases are supposed to occupy zero volume is called Absolute zero.
    • All gases obey Charles’ law at very low pressures and high temperatures
    Gay Lussac’s Law
    • Pressure- Temperature Relationship
    • Pressure in well inflated tyres of automobiles is almost constant, but on a hot summer day this increases considerably and tyre may burst if pressure is not adjusted properly.
    • During winters, on a cold morning one may find the pressure in the tyres of a vehicle decreased considerably.
    • At constant volume, pressure of a fixed amount of a gas varies directly with the temperature. Mathematically. P/T = constant.
    • This relationship can be derived from Boyle’s law and Charles’ Law.
    • Pressure vs temperature (Kelvin) graph Each line of this graph is called isochore.
    Avogadro Law,Italy, 1811 Volume – Amount RelationshipEqual volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.As long as the temperature and pressure remain constant, the volume depends upon number of molecules of the gas V=k4n.
    STP
    • Standard temperature and pressure means 273.15 K (0°C) temperature and 1 bar (i.e., exactly 105 pascal) pressure.
    • These values approximate freezing temperature of water and atmospheric pressure at sea level.
    Dalton Partial pressure, 1801
    • Total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases
    • In a mixture of gases, the pressure exerted by the individual gas is called partial pressure.
    • pTotal = p1 +p2 +p3 +…..
    gas liquification
    • At 30.98 C carbon dioxide remains gas upto 73 atmospheric pressure. At 73 atmospheric pressure, liquid carbon dioxide appears. Therefore, 30.98 C is called critical temperature of carbon dioxide. Because this is the highest temperature at which liquid carbon dioxide is observed.
    • A gas below the critical temperature can be liquefied by applying pressure, and is called vapour of the substance.
    Ideal Gas vs. Real gas
    Ideal Gas Real Gas
    Ideal gas follows Boyle’s law, Charles’ law and Avogadro law strictly-at all temperature and pressures. They do not follow, Boyle’s law, Charles law and Avogadro law perfectly under all conditions.
    Ideal gas equation: pV=nRT is applicable to them N/A
    Such a gas is hypothetical, it goes on assumption that intermolecular forces present in an ideal gas. Their molecules interact with each other.
    N/A
    • Boyle temperature: At this temperature real gas obeys ideal gas law.
    • This Boyle point/temperature of a gas depends upon its nature.

    Periodic Table

    Historic attempts
    chemist table name
    Johann Dobereiner (German) Triads
    AEB De Chancourtois (French) cylindrical table
    Lothar Meyer (German) His table closely resembles the Modern Periodic Table. But his work published after Mendeleev. Therefore, Mendeleev credited with Modern Periodic Table.

    Block elements

    chemistry elements properties
    We can classify the elements into four blocks depending on the type of atomic orbitals that are being filled with electrons

    s-block Group 1 (alkali metals) and Group 2 (alkaline earth metals)
    p-block Representative Elements or Main Group Elements
    d-block
    • Transition Elements.
    • They mostly form coloured ions
    • they display paramagnetism (i.e. attracted by magnetic field)
    • They are used as catalysts
    f-block
    • Inner-Transition Elements
    • They are all metals.
    • located in bottom two rows of the table.
    • two rows of elements at the bottom of the Periodic Table, called the Lanthanoids and Actinoids,
    • Actinoid elements are radioactive.
    • Most actinoid elements found only in nanogram quantities during nuclear reactions and their chemistry is not fully studied.
    • The elements after uranium are called Transuranium Elements.

     

    Cation vs Anion
    cation anion
    removal of an electron from an atom leads to cation Gain of an electron leads to an anion.non-metals have strong tendency to gain electrons.
    Smaller than parent atom, because less electrons. Larger than parent atom.

    Our own publications are available at our webstore (click here).
    For Guidance of WBCS (Exe.) Etc. Preliminary , Main Exam and Interview, Study Mat, Mock Test, Guided by WBCS Gr A Officers , Online and Classroom, Call 9674493673, or mail us at – mailus@wbcsmadeeasy.in
    Please subscribe here to get all future updates on this post/page/category/website
    WBCS Feedburner Subscription

    Leave a Reply

    Your email address will not be published. Required fields are marked *

    This site uses Akismet to reduce spam. Learn how your comment data is processed.

    WBCS Foundation Course Classroom Online 2024 2025 WBCS Preliminary Exam Mock Test WBCS Main Exam Mock Test WBCS Main Language Bengali English Nepali Hindi Descriptive Paper