Chemistry, Matter and its Composition
Category : UPSC
CHEMISTRY, MATTER AND ITS COMPOSITION
CHEMISTRY AND ITS IMPORTANCE
Chemistry is the study of matter and the changes that material substances undergo.
Handy Facts
New branches in chemistry are emerging because of research being carried in the quest to make life more comfortable. One good example is Green Chemistry, which deals with development of safer products and manufacturing processes for a sustainable future.
THE IMPORTANCE AND SCOPE OF CHEMISTRY
Chemistry plays an important role in every aspect of our daily lives. It is a central science that connects all the other sciences and helps them to achieve what they do.
Food Science
Food science is the study of the physical, biological, and chemical make-up of food and the concepts underlying food processing. The contribution of chemistry to Food Science has been manifold.
Science in Action
Not all additives added to food are healthy. For example, potassium bromate (\[K{{B}_{r}}{{O}_{3}}\]) used in bread-making is an oxidizing agent that is used to ‘’mature” bread flour, which helps strengthen the dough and improve rising, giving it move volume.
Agriculture
In the field of Agriculture, chemistry has provided:
Medicine
Chemistry has contributed towards the science of Medicine in a number of ways:
(i) Analgesics: reduce pain, e.g. paracetamol, aspirin, etc.
(ii) Antibiotics: cure infections and cure many diseases, e.g. Chloromycetin, streptomycin, etc.
(iii) Tranqullizers: reduce tension and bring about calm and peace to mental patients, e.g. chlorpromazine, diazepam (Valium), etc.
(iv) Antiseptics: stop infection of wounds, e.g. Dettol
(v) Anaesthetics: make patients senseless before surgical operations, e.g. Barbiturates, Benzodiazpines, etc.
Science in Action
Chemistry is providing new materials for medical use. Diseased or weakened arteries can be replaced surgically with tubes made of Dacron polymers.
Energy
The use of chemistry in the field of energy has been found contributing in:
Environmental Science
Environmental changes and chemistry are inextricably linked.
Biology and Biotechnology
Chemistry has helped
Geology
In geology, chemical techniques are mostly required:
Oceanography
In Oceanography, chemistry is mostly used to:
Archaeology
Archaeology yields information and develops theories about past human activity by means of a study of ancient material remains. Some applications of chemistry in this field are in the:
Forensic Science
Forensic science means applications of scientific procedures to legal problems particularly during investigations. Chemical methods are used to analyze sample of investigation.
Science in Action
Chemistry has made our life easy by giving innumerable materials. Steel, bronze and brass are mixtures that have
been used since ancient times as structural materials. Tiles made from ceramic are used on a space shuttle help to protect it is from overheating. Optical fiber is used in communication. It is made mainly from silicon dioxide
(\[Si{{O}_{2}}\]) which is found in sand. The chip used in computers is also made up of silicon.
Handy Facts
Linus Pauling is the only person to be awarded two unshared Nobel Prizes-one in 1954 for Chemistry and the other in Peace in 1962.
CHEMICALS OF COMMON USE
There are many chemicals that are most essential in daily life. These chemicals are used either in combined form or as some reagents. The list of few chemicals and their most common uses is given in the following table:
|
Common Name |
Molecular Formula (Chemical name) |
Common Uses as/in |
|
Baking powder |
\[NaHC{{O}_{3}}\] sodium bicarbonate) |
Baking & cooking, |
|
Soap |
Esters |
Bathing & Washing |
|
Detergent |
Sodium sulphate, sodium hydroxide & phosphate compounds |
Washing clothes |
|
Table Salt |
NaCl (Sodium Chloride) |
Kitchen Salt |
|
Vinegar |
\[{{C}_{2}}{{H}_{4}}{{O}_{2}}\] (Ethanoic acid) |
Preservative |
|
Graphite |
C (Carbon) |
Pencil |
|
Bleaching Powder |
Sodium hypochlorite (NaOCI) |
Cleaning & sterilizing drinking water, swimming pools, etc. |
|
Sugar |
Sucrose (\[{{C}_{12}}{{H}_{22}}{{O}_{11}}\]) |
Sweetener |
|
Aspirin |
\[{{C}_{9}}{{H}_{8}}{{O}_{4}}\]( Acetyl salicylic acid) |
Medicine |
|
Peroxide |
\[{{H}_{2}}{{O}_{2}}\] (Hydrogen peroxide) |
Mouthwash (hygiene) |
|
Caustic soda. Lye |
NaOH ( Sodium hydroxide) |
Cleaning, unblocking sinks drains and toilets in different industries, etc. |
|
Moth balls |
\[{{C}_{6}}{{H}_{4}}{{C}_{12}}\] (1,4-dichlorobenzene) |
Dispel moths(an insect) |
|
Green vitriol |
\[FeS{{O}_{4}}.5{{H}_{2}}O\] (Ferrous Sulphate) |
Anamic patients for supplementing iron |
|
Sodium Fluoride |
NaF |
Toothpaste |
|
Glucose |
\[{{C}_{6}}{{H}_{12}}{{O}_{6}}\] (D-glucose) |
Energy source for organisms |
|
Ammonia |
\[N{{H}_{3}}\] |
Manufacturing urea |
|
Butane |
\[{{C}_{4}}{{H}_{10}}\] (n-butane) |
A component of LPG |
|
Sulfuric Acid |
\[{{H}_{2}}S{{O}_{4}}\] (Sulphuric acid) |
Industrial Product |
|
Marsh gas/Natural gas |
\[C{{H}_{4}}\] (Methane) |
Fuel |
|
Saccharine |
\[{{C}_{7}}{{H}_{5}}N{{O}_{3}}S\] |
Artificial Sweetener |
|
Tartaric acid |
\[{{C}_{4}}{{H}_{6}}{{O}_{6}}\] (2, 3-dihydroxybutanedioic acid) |
Fermentation of grapes |
|
Laughing Gas |
\[{{N}_{2}}O\] (Nitrous Oxide) |
Laughing gas |
|
Citric Acid |
\[{{C}_{6}}{{H}_{8}}{{O}_{7}}\] (2-hydroxypropane-1,2,3-tricarboxylic acid) |
Preservative |
|
Octane |
\[{{C}_{8}}{{H}_{18}}\] (n-octane) |
Component of petrol |
|
Camphor |
\[{{C}_{10}}{{H}_{16}}O\] (l,7,7-Trimethylbicyclo[2.2.1]heptan-2-one) |
Fragrance |
|
Formaldehyde |
\[C{{H}_{2}}O\], (Formaldehyde) |
Preservatives of corpses. |
|
Alpha-Propylene Glycol |
\[{{C}_{3}}{{H}_{8}}{{O}_{2}}\] ( Propane-1,2-diol) |
Moisturizing Skin |
|
Triethanolamine |
\[{{C}_{6}}{{H}_{15}}N{{O}_{3}}\] (2- [bis (2-hydroxyethyl)ammo ethanol) |
Lotion, shaving foams, shampoo, etc. ,.J |
|
Acetone |
\[{{C}_{6}}{{H}_{6}}{{O}_{{}}}\] ( Propanone) |
Removal of residues, glue, stains & paint. |
|
Plaster of Paris |
\[CaS{{O}_{4}}.1/2{{H}_{2}}O\] (Calcium Sulphate hemihydrates) |
Plastering fractured bones |
|
Blue Vitriol |
\[CuS{{O}_{4}}.5{{H}_{2}}O\] (Copper Sulphate) |
Colorant |
|
Chloroform |
\[CHC{{I}_{3}}\] (Trichloro Methane) |
Anesthetic. |
|
Chalk (Marble) |
\[CaC{{O}_{3}}\] (Calcium Carbonate) |
Architecture, sculpture. |
|
Caustic Potash |
KOH (Potassium Hydroxide) |
Cleaner, fertilizer, etc. |
|
Dry Ice |
\[C{{O}_{2}}\] (Solid Carbon dioxide) |
Preserving degradable items |
|
Gypsum |
\[CaS{{O}_{4}}\] (Calcium Sulphate) |
Fertiliser & Constituent of plaster, blackboard chalk and wallboard. |
|
Heavy Water |
\[{{D}_{2}}O\] (Deuterium Oxide) |
Moderator in nuclear reactor |
|
Slaked Lime |
\[Ca{{(OH)}_{2}}\] (Calcium Hydroxide) |
pH-regulating agent and acid neutralizer in soil and water. |
|
Potash Alum |
\[{{K}_{2}}AI{{(S{{O}_{4}})}_{3}}\] (Potassium Aluminium Sulphate) |
Water purification |
|
Quick Lime. |
CaO (Calcium Oxide) |
Whitewash |
|
Mohr?s Salt |
\[FeS{{O}_{4}}{{(N{{H}_{4}})}_{2}}S{{O}_{4}}.6{{H}_{2}}O\] (Ammonium Ferrous Sulphate) |
Analytical reagent in laboratory |
|
White Vitriol |
\[ZnS{{O}_{4}}.7{{H}_{2}}O\] (Zinc Sulphate) |
Medicine |
|
Magnesia |
MgO ( Magnesium oxide) |
Soil and ground water treatment |
|
Vermelium |
HgS (Mercuric Sulphide) |
Pigment |
|
T.N.T. |
\[{{C}_{7}}{{H}_{5}}{{N}_{3}}{{O}_{6}}\] (Trinitrotoluene) |
Explosive |
|
Sand |
\[Si{{O}_{2}}\] |
Manufacturing glass, etc. |
|
Calcium Sulphate |
\[CaS{{O}_{4}}.2{{H}_{2}}O\] |
Cement industry |
|
Borax |
\[N{{a}_{2}}{{B}_{4}}{{O}_{7}}.10{{H}_{2}}O\] (sodium tetraborate decahydrate) |
Washing |
|
Brimstone |
S (Sulphur) |
In industry |
|
Cream of tartar |
\[KH{{C}_{4}}{{H}_{4}}{{O}_{6}}\] (Potassium hydrogen tartrate) |
Baking to stabilize eggs and creams, as well |
|
Epsom salt |
\[MgS{{O}_{4}}.7{{H}_{2}}O\] (Magnesium sulphate heptahydrate) |
Food additives as salt. |
|
Freon |
\[C{{F}_{2}}C{{I}_{2}}\] (Dichlorodifluoromethane) |
Refrigerant & aerosol propellants |
|
Galena |
PbS. (Lead sulphide) |
Lead-acid batteries |
|
Grain alcohol |
\[{{C}_{2}}{{H}_{5}}OH\] (Ethanol) |
Alcoholic drinks, fuel & solvent |
|
Hypo |
\[N{{a}_{2}}{{S}_{2}}{{O}_{3}}\] (Sodium thiosulphate) |
Film photographic paper processing |
|
Milk of magnesia |
\[Mg{{(OH)}_{2}}\] (Magnesium hydroxide) |
Antacid |
|
Muriatic acid |
HCI (Hydrochloric acid) |
Industrial substance |
|
Gammexene |
\[{{C}_{6}}{{H}_{6}}C{{I}_{6}}\] (l,2,3,4,5,6-hexachlorocyclohexane) |
Insecticide |
|
Potash |
\[{{K}_{2}}C{{O}_{3}}\] Potassium carbonate) |
Fertilizer |
|
Iron pyrites (Fool?s gold) |
\[Fe{{S}_{2}}\] (Iron disulphide) |
Source of sulphur and Iron |
|
Quartz |
\[Si{{O}_{2}}\] (Silicon -di-oxide) |
Silicon dioxide |
|
Quicksilver |
Hg (mercury) |
Thermometers |
|
Rubbing alcohol |
\[{{(C{{H}_{3}})}_{2}}CHOH\] ( isopropyi alcohol or Propan-2-ol) |
Antiseptic |
|
Sal ammoniac |
\[N{{H}_{4}}CI\] (ammonium chloride) |
Crisping agent for food and spice |
|
Salt substitute |
KCI (potassium chloride) |
Treating low blood levels of potassium (hypokalemia) |
|
Saltpeter |
\[KN{{O}_{3}}\] (potassium nitrate) |
Food preservatives & fireworks |
|
TSP (Trisodium phosphate) |
\[N{{a}_{3}}P{{O}_{4}}\] (Sodium phosphate) |
Emulsifiers (in cheese), thickening agents, & leavening agents for baked goods. |
|
Wood alcohol |
\[C{{H}_{3}}OH\] (Methanol) |
Antifreezing, solvent, fuel, denaturant for ethanol |
|
Phenol |
\[{{C}_{6}}{{H}_{5}}OH\] (Phenol) |
Antiseptic |
|
Tincture of iodine |
A solution of iodine along with potassium iodide or sodium iodide in water and ethanol mixture |
Disinfectant |
|
MSG or Chinese salt |
\[{{C}_{5}}{{H}_{8}}NNa{{O}_{4}}\] (Mono-sodium glutamate) |
Food-additive |
|
Silica |
\[Si{{O}_{4}}\] (Silicon-di-oxide) |
Dehydrating agent |
|
Vitamin C |
\[{{C}_{6}}{{H}_{8}}{{O}_{6}}\] (Ascorbic acid ) |
Vitamin |
|
Smelling Salt |
\[{{(N{{H}_{4}})}_{2}}C{{O}_{3}}.{{H}_{2}}O\]) (Ammonium Carbonate) |
Substance to revive fainted man |
|
Chrome Green |
\[C{{r}_{2}}{{O}_{3}}\] (Chromium trioxide) |
Green pigment |
|
Oil of Clove |
\[C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}{{C}_{6}}{{H}_{3}}(OC{{H}_{3}})OH\] (Eugenol) |
Relieving pain in teeth |
|
Talc |
\[M{{g}_{3}}S{{i}_{4}}{{O}_{10}}{{(OH)}_{2}}\] (Magnesium Silicate) |
Talcum powder |
|
Carborundum |
SiC (Silicon Carbide) |
Abrasive material |
|
Permanganate of potash or Condy?s crystals, |
\[KMn{{O}_{4}}\] (Potassium Permanganate) |
Disinfectant |
|
Gobar Gas(Bio gas) |
Mixture of methane (\[C{{H}_{4}}\]) and carbon dioxide (\[C{{O}_{2}}\]) and small amounts of hydrogen sulfide (\[{{H}_{2}}S\]), moisture and siloxanes |
Fuel in cooking |
|
T.N.T |
\[{{C}_{6}}{{H}_{2}}C{{H}_{3}}{{(N{{O}_{2}})}_{3}}\] (Tri nitro toluene) |
Explosive material |
|
Tear gas |
\[CC{{I}_{3}}N{{O}_{2}}\] (2-Chlorobenzalmalononitrile) |
Controlling riots, etc. |
|
Aqua-regia |
Conc. \[{{H}_{2}}S{{O}_{4}}\]+ Conc. HCl |
Laboratory reagent |
|
Urea |
\[N{{H}_{2}}CON{{H}_{2}}\] |
Fertilizer |
|
Westron |
\[CHC{{I}_{2}}-CHC{{I}_{2}}\] (1,1,2,2-tetrachloroethane) |
Solvents for paints and varnishes |
|
Pyrene |
\[CC{{I}_{4}}\] (Carbon tetra-chloride) |
Fire-extinguisher . |
MATTER AND ITS COMPOSITION
The universe is made up of matter and energy.
Matter: Matter describes the physical things around us: the earth, The air we breathe, the pencil with which we write, etc.
Energy: It is the ability to cause change or do work. Some forms of energy include light, heat, chemical, nuclear, electrical and mechanical energy.
The matter can be classified in two different ways;
Handy Facts
Most of the evidences for the existence of particles in matter come from the experiments on the phenomene Diffusion and Brownian motion. Diffusion is the process in which particles constituting a matter move from a higher concentration to a lower concentration. This process happens at random. Diffusion can happen in a gas or liquid but cannot take place in a solid object. Particles in both liquids and gases (collectively called fluids) move randomly. This is called Brownian motion. Brownian motion is named after the botanist Robert Brown.
The Physical States of Matter
Matter is found in three physical states, i.e. Solid,
Liquid and Gas. These states are also known as phases of matter. The difference in the physical states of matter is due to the arrangement of the particles of which the matter is made of.
Almost all chemical substances can exist in more than one physical state (phase) depending on external pressure and temperature.
|
|
States of Matter |
|
|
|
\[\downarrow \] |
\[\downarrow \] |
\[\downarrow \] |
|
|
Solid |
Liquid |
Gas |
|
|
• Definite shape |
• Indefinite shape; takes the shape of the container |
• Indefinite shape |
|
|
• Definite volume |
• Definite volume |
• Indefinite volume |
|
|
• Highest density |
• Density is lower than solid |
• Lower density |
|
|
• Cannot flow |
• Flow |
• Flow |
|
|
• Maximum force of attraction amongst the particles |
• Less force of attraction amongst the particles. |
• Negligible force of attraction amongst the particles |
|
|
• Particles are tightly packed |
• Particles are loosely packed as compared to solids |
• Particles are loosely packed |
|
|
• Cannot be compressed |
• Can be compressed |
||
|
• Particles cannot move, rather they vibrate only at their fixed position |
• Cannot be compressed |
• Particles can move freely |
|
|
• Particles can slide over one another |
|
||
|
• Kinetic energy of the particles is minimum |
|
|
|
Handy Facts
Two other forms of matter are Plasma and Bose-Einstein condensate Plasma consists of highly charged particles with extremely high kinetic energy. The noble gases (helium, neon, argon, krypton, xenon and radon) are after used to make glowing signs by using electricity to ionize them to the plasma state.
Solid
Solids can be divided into two distinct classes.
|
|
Solid |
|
||
|
|
\[\downarrow \] |
\[\downarrow \] |
|
|
|
Crystalline Solids |
Amorphous solids |
|||
|
· Have characteristic geometrical shape. |
· Solids that don’t have a definite geometrical shape. · Particles are randomly arranged in three dimensions. |
|||
|
· Possesses highly ordered three- dimensional arrangements of particles. |
· Don’t have sharp melting points. |
|||
|
· Bounded by Planes or faces |
· Formed due to sudden cooling of liquid. |
|||
|
· Planes or a crystal intersect at particular angles. |
· Melt over a wide range of temperature. · Examples: · Coal. Coke, Plastic, rubber, etc. |
|||
|
· Have sharp melting and boiling points. · Examples: · Copper Sulphate \[(CuS{{O}_{4}}),NiS{{O}_{4}}\], Diamond, Graphite, NaCI, Sugar, etc. |
|
|||
Liquid
Like solids, the volume of a liquid is slightly altered by variations in temperature and pressure.
Liquids have three typical physical properties:
Gases
Gas is the third state of the matter. Gases have three characteristic properties:
EFFECT OF TEMPERATURE AND PRESSURE ON STATES OF MATTER
Physical change of matter from one phase to another phase occurs on adding energy to matter. For example:
Physical change also can be caused by motion and pressure. Physical processes undergone by matter leading to changes in the phases of the system are:
Melting and freezing
The melting point (or, also sometimes called liquefaction point) of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure.
Science in Acton
The freezing point is the temperature at which a liquid changes to a solid. As the liquid is cooled, particle motion slows.
Handy Facts
Most liquids contract as they freeze. One of the important characteristics of water is that it expands when it freezes, so ice floats.
Adding dissolved substances, or solutes, to a liquid will depress the freezing point.
Super Cooled liquid
Liquids can be cooled to temperatures well below their melting point before they begin to solidify. Such liquids are said to be “super cooled” and often require the presence of a dust particle or “seed crystal” to start the process of crystallization.
Science in Action
The freezing point of pure water is \[{{0}^{o}}C\], but that melting point can be decreased by adding freezing or salt. The use of ordinary salt (sodium chloride, i.e. NaCI) on icy roads in the winter helps to melt the ice from the roads by lowering the melting point of the ice.
Sublimation
Sublimation is a chemical process where a solid turns into a gas without going through the liquid phase.
Examples of substance which sublime
Vapourisation
Vapourisation is the conversion of a liquid to a gas.
|
Evaporation |
Boiling |
|
• Evaporation takes place at all temperatures, |
• boiling occurs at a particular temperature. |
|
• Evaporation takes place from the surface, |
• Boiling is a bulk phenomenon. |
The temperature at which a liquid boils is called boiling point.
Science in Action
Food takes longer time to get cooked at high altitude. At high altitudes, the atmospheric pressure is lower than that at sea level, so the boiling point at high altitudes is quite low, which means water boils very fast at low temperatures. The food inside it does not get enough heat to get cooked and thus food is difficult to be cooked at high altitudes. Using a pressure cooker at such conditions helps increase the boiling time as the pressure inside the pressure cooker increases due to the vapour produced inside it.
Condensation and Deposition
Condensation is the change of the physical state of matter from gas phase into liquid phase.
Condensation is the opposite of evaporation.
When the gas transforms directly into a solid, without going through the liquid phase, it is called deposition or de-sublimation.
Example: Conversion of water vapour in the atmosphere into frost or ice at sub-freezing temperatures. Frost tends to outline solid blades of grass and twigs because the air touching these solids cools faster than air that is not touching a solid surface.
ELEMENT, MIXTURE AND COMPOUNDS
According to chemical composition, matter can be classified as
ELEMENTS
Elements are the simplest form of chemical substances that cannot be broken down by ordinary chemical means. Examples are hydrogen (H), sulphur (S) or gold (Au), etc.
The building blocks of the Universe are the elements. The term element was first used by Robert Boyle.
Handy Facts
Most of the elements are solids, while eleven of them are gasses and only two are liquids. Of the two liquids, mercury is a metal and bromine is non-metal. However, two other metals can also exist in the liquid state at around \[{{30}^{o}}C\]. These two are gallium and caesium.
COMPOUNDS
A compound is a substance composed of two or more elements which are chemically combined. Examples of compounds are water, sugar and salt, etc.
|
|
Compounds |
|
||
|
\[\downarrow \] |
\[\downarrow \] |
\[\downarrow \] |
||
|
Specific elements present For example: |
Bonding in the compound For example |
Reactivity-type of chemical reactions For example: |
||
|
• Oxides contain one or more oxygen atoms, hydrides contain one or more hydrogen atoms, and halides contain one or more halogen. |
• Ionic compounds contain ions and are held togeter by the attractive forces among the oppositely charged ions. Common saslt (sodium chloride) is one of the best-lnown ionic compounds. |
• Acids are compounds that produce \[{{H}^{+}}\] ions (protons) when dissolved in water to produce aqueous solutions. The most common acids are aqueous solution of HCI (hydrochloric acid), \[{{H}_{2}}S{{O}_{4}}\](suplhuric acid), \[HN{{O}_{3}}\](nitric acid), and \[{{H}_{3}}P{{O}_{4}}\](phosphoric acid). |
||
|
• Organic and inorganic compounds contains carbon and few other elements like hydrogen, oxygen, nitrogen, sulphur, halogens. Earlier, these were obtained from animals and plants. |
• Molecular compounds contain discrete molecules, which are held together by sharing electrons (covalent bonding). Examples: water (\[{{H}_{2}}O\]) methane (\[C{{H}_{4}}\]) etc. |
• Bases are proton acceptors. e.g. NaOH (sodium hydrocide), etc |
||
|
• Inorganic compounds contain any two or more elements out of 118 elements. These are usually obtained from minerals and rocks. |
|
|
||
MIXTURES
Mixtures are all around us. For example, a salad is a mixture of vegetables, a glass of soda is a mixture of water,
|
|
Mixtures |
|
|
|
|
\[\downarrow \] \[\downarrow \] |
|
|
|
Homogenous mixtures |
Heterogeneous mixtures |
||
|
· Same composition throughout |
· No definite composition |
||
|
· Do not separate into phases when left alone. |
· Separate into phases when left alone. |
||
|
· Any homogeneous mixtures are solutions that consist of a solute and a solvent. Example: An alloy is a solution of two or more elements, at least one of which is a metal, where the resulting material has metallic properties. |
· Can be separated by ordinary physical means. Example: Blood, Oil and water, etc. |
||
Methods of Separation of the Components of Mixtures
To separate different components of a mixture, varieties of physical techniques are available. Based on difference in the physical properties of the components present in the mixture.
Separation by Using Separating Funnels
A separating funnel is used for the separation of components of a mixture between two immiscible liquid phases. One phase is the aqueous phase and the other phase is an organic solvent. This separation is based on the differences in the densities of the liquids.
Separation by Evaporation
The separation of liquid (solvent) and solid (solute) from a solution is done by removing the liquid (solvent) by heating or by solar evaporation. By evaporation we can recover the solute component only in solid or powder form.
Separation by Filtration
Filtration is a better method for separating solids from liquids in heterogeneous mixtures. In filtration the solid material is collected as a residue on filter paper and the liquid phase is obtained as filtrate.
Applications: Salt (water soluble) and sand (water insoluble) using water as solvent
Sulphur (soluble in\[C{{S}_{2}}\]) and glass powder (insoluble in\[C{{S}_{2}}\]) using \[C{{S}_{2}}\]as solvent.
Centrifugation
Sometimes the solid particles in a liquid are very small and can pass through a filter paper. For such particles, the filtration technique cannot be used for separation. Such mixtures are separated by centrifugation. So, centrifugation is the process of separation of insoluble materials from a liquid where normal filtration does not work well.
During centrifugation the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.
Applications: Used in
Simple Distillation
Simple distillation is a method used for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient difference in their boiling points.
Applications:
Fractional Distillation
Fractional distillation is used for the separation of a mixture of two or more miscible liquids for which the difference in boiling points is less than 25K.
Applications: Separation of
|
Name of the fraction (% in crude oil) |
No. of C-atoms |
Boiling range |
Use |
|
Fuel Gas, LPG, refinery gas (1-2%) |
1 to 4 (mainly propane & butane which can be liquefied |
25%C |
Bottled gas |
|
Petrol |
5 to 7 |
25 to \[75{}^\circ C\] |
Fuel for cars |
|
Naptha (20-40%) |
6 to 10 |
75 to \[190{}^\circ C\] |
Making chemical |
|
Paraffin, kerosene (10-15%) |
10 to 16 |
190 to \[250{}^\circ C\] |
Aircraft fuel |
|
Diesel (15-20%) |
14 to 20 |
250 to \[350{}^\circ \] |
Fuel for cars, lorries, buses |
|
Fuel oil, lubricating oils, waxes and bitumen (40-50%) |
over 20 to several hundred |
high boiling liquids or low melting solids that boil over \[350{}^\circ C\] |
Fuel oil is used as fuel for ships, power stations. Bitumen is used for roads and roops. |
Chromatography
Chromatography involves passing a mixture of different dissolved substances in a "mobile phase" through another material called a stationary phase, which separates the analyte to be measured from other molecules in the mixture and allows it to be isolated.
The mobile phase may be a gas or liquid. The mobile phase is then passed through stationary phase. The stationary phase may be a solid packed in a glass plate or a piece of Chromatography paper.
The various chromatographic techniques are:
Paper Chromatography is one of the important chromatographic methods.
Applications: To separate
SOLUTION
A solution (a homogeneous mixture) is formed when one or more substances (the solute) are completely dissolved in another substance (the solvent). Depending on the nature of the solvent and solute we can have following kinds of solutions.
|
Different kinds of solution |
|||
|
Solute |
Solvent |
State of Resulting Solution |
Example |
|
Gas |
Gas |
Gas |
Air |
|
Gas |
Liquid |
Liquid |
Soda water (\[C{{O}_{2}}\] in water) |
|
Gas |
Solid |
Solid |
\[{{H}_{2}}\] gas in palladium |
|
Liquid |
Liquid |
Liquid |
Ethanol in water |
|
Solid |
Liquid |
Liquid |
NaCI in water |
|
Solid |
Solid |
Solid |
Brass (Cu/Zn), solder (Sn/Pb) |
When a substance dissolves in a solvent it is said that the particular solute is soluble in that particular solvent. If it does not dissolve then it is insoluble.
Water as a solvent
Water is a commonly used solvent as it dissolves a large number of substances. Because of this property water is called a universal solvent.
Strengths of Solution
Quantitative study of a solution requires its concentration, that ss. the amount of solute present in a given amount of solution.
The three most common units of concentration are percent by mass, molarity, and molality.
Percent by Mass: The percent by mass (also called the percent by weight or the weight percent).
% By mass = \[\left( \frac{Mass\,\,of\,\,solute}{Mass\,\,of\,\,solvent} \right)\times 100\]
The percent by mass has no units because it is a ratio of two similar quantities.
Molarity (M): It is the number of moles of solute dissolved in one liter of the solution.
Thus, molarity has the units of mole per liter (mol/L).
Molality (m): Molality is the number of moles of solute dissolved in 1 kg (1000 g) of solvent.
Molality = moles of solute (mass of solvent)/1 kg
Colligative Properties of Solutions
Several important properties of solutions depend on the number of solute particles in solution and not on the nature of the solute particles. These properties are called colligative properties (or collective properties) because they are bound together by a common origin; The colligative properties are:
Osmotic Pressure
not to solute is called a semi permeable membrane. Osmotic pressure may be defined as the external pressure applied to the solution in order to stop the osmosis of solvent into solution separated by a semi permeable membrane.
Science in Action
Reverse osmosis is one of the processes that makes desalination (or removing salt from seawater) possible. It is the process of osmosis in reverse. Where osmosis occurs naturally without energy required, to reverse the process of osmosis, energy is required to be applied to the more saline solution.
SUSPENSION AND COLLOID
Depending on the size of the particles suspended, or dispersed in the surrounding medium, heterogeneous mixtures can be divided into the followings:
The following table summarizes the major properties and points of distinction between each type of solution with respect to different properties.
Properties of colloids, true solutions and suspension
|
Property |
True Solution |
Colloidal Solutions |
Suspension |
|
Size of the particles |
< 1 nm |
1- 1000 nm |
>1000 nm |
|
Nature |
Homogeneous |
Heterogeneous |
Heterogeneous |
|
Filterability (Diffusion Trough parchment paper) |
Particles of true Solution diffuse rapidly through filter paper as well as parchment paper. |
Colloidal particles pass through filter paper but not through parchment paper. |
Suspension particles do not pass through filter paper and parchment paper. |
|
Visibility |
Particles of True Solution are not visible to naked eye. |
Colloidal particles are not seen to naked eye but can be studied through ultra-microscope. |
Suspension particles are big enough to be seen by naked eye. |
|
Tyndal effect |
True Solution does not show Tyndall effect. |
Colloids show Tyndall effect. |
Suspension may or may not show Tyndall effect. |
|
Appearance |
Transparent |
Translucent |
Opaque |
Classification of Colloids
Colloids are also called colloidal dispersions because the substances remain dispersed and do not settle to the bottom of the container.
Different Kinds of Colloids
|
Dispersed Phase |
Dispersion Medium |
Type of Colloid |
Example |
|
Solid |
Solid |
Solid sol |
Ruby glass. Gem stone |
|
Liquid |
Solid |
Solid emulsion/gel |
Pearl, cheese |
|
Gas |
Solid |
Solid foam |
Lava, pumice |
|
Solid |
Liquid |
Sol |
Paints, cell fluids |
|
Liquid |
Liquid |
Emulsion |
Milk, oil in water |
|
Gas |
Liquid |
Foam |
Soap suds, whipped cream |
|
Solid |
Gas |
Aerosol |
Smoke |
|
Liquid |
Gas |
Aerosol |
Fog, mist |
Gases cannot form a colloidal solution between themselves, because they form homogenous mixtures.
Determination of a Colloid
Following two methods can be used to determine whether a mixture is colloid or not.
Science in Action
Kidney Dialysis, also known as hemodialysis, is a medical method to remove waste materials from the blood of patients suffering from kidney malfunction.
Applications of suspensions and colloids
For example Barium sulfate in suspension is frequently used medically as a radio contrast agent for x-ray imaging and other diagnostic procedures. Colloids are also very important in the medical field because they can be used to manipulate blood conditions. To be specific, colloids are often used to regulate colloidal osmotic pressure, a pressure applied by proteins in the blood to pull water in the vascular system.
PHYSICAL AND CHEMICAL CHANGES
To understand the difference between a pure substance and a mixture, let us understand the difference between a physical and a chemical change.
Physical Change
During physical changes a substance changes its physical appearance, but not its composition. All changes of state (for example, from liquid to gas or from liquid to solid) are physical changes.
Characteristics of Physical Changes
Some Examples Involving Physical Changes
|
Physical changes |
Observation |
Change on physical property |
|
• Switching of an electric bulb. |
The bulb glows and gives out heat and light energy. |
The physical appearance of the bulb changes. |
|
• Rubbing a permanent magnet on a steel rod. |
The steel rod gets magnetised. If it is brought near iron nails, they get attracted. |
The steel rod acquires the property of attracting pieces of iron. |
|
• Action of heat on iodine |
The brownish grey crystals of iodine change to form violet vapours. On cooling the vapours condenses to for form crystals. |
Change in state and colour. |
|
• Dissolving of common salt in water. |
The white crystalline salt disappears in water. However, the water tastes exactly like common salt. Moreover, common salt can be recovered by evaporation |
Change of state. |
Chemical Change
A chemical change is one in which the identity of the original substance is changed and a new substance or new substances are formed.
e.g., souring of milk burning of paper, burning of candle, etc.
In the burning of candle, the wax of a candle bums into ash and smoke.
Characteristics of a Chemical Change
Some Examples Involving Chemical Changes:
|
Chemical change |
Observation |
Chemical equation |
|
• Burning of magnesium in air |
When a magnesium ribbon is heated in a flame of Bunsen burner, it catches fire and bums with dazzling white flame to form white ash. |
Magnesium + Oxygen\[\xrightarrow[{}]{{}}\] Magnesium oxide |
|
• Rusting of iron |
When iron (silver grey) is left exposed to moist air for a few days, reddish brown powdery mass (rust) is found on its surface. |
(from air) \[\xrightarrow[{}]{{}}\] Iron + Oxygen + Water vapours \[\xrightarrow[{}]{{}}\] Rust |
|
• Burning of LPG |
When LPG (liquefied petroleum gas) is burnt, it bums with a pale blue flame and liberates colorless gas carbon dioxide along with steam. |
Butane (LPG) + Oxygen \[\xrightarrow[{}]{{}}\] Carbon dioxide + Water |
Handy Facts
Chemical weathering is the process by which rocks are broken down by chemical reactions. Rocks look different from each other because of chemical weathering. Different types of chemical weathering’s are:
Some interesting information about elements
(a) The most abundant element in the universe -Hydrogen(H)
(b) The most abundant element in the earth's crust -Oxygen(0)
(c) The most abundant metallic element in the earth’s crust- Aluminum (Al)
(d) The most abundant element in the earth's atmosphere –Nitrogen (N)
(e) The element having the highest density at room temperature –Osmium (Os)
(f) The lightest metal at room temperature-Lithium (Li)
(g) The metal having the highest melting point and boiling point –Tungsten (W)
(h) The element with the highest melting point -Carbon (C)
(i) The element having lowest melting point and boiling point-Helium (He)
(j) The metal having the lowest melting point and boiling point –Mercury (Hg)
(k) The most ductile metal –Silver (Au)
(l) The element having highest number of isotopes- Silver (Ag)
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