# UPSC Chemistry States of Matter Chemistry, Matter and its Composition

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:

• Better understanding of the processes like photosynthesis, nitrogen fixation, etc. This has led to development of more productive plants.
• Chemical fertilizers like urea, potash, etc. have led to increase food production helping countries to fight food shortage.
• Insecticides, pesticides and fungicides that are used to protect crops.

Medicine

Chemistry has contributed towards the science of Medicine in a number of ways:

• It has given life saving drugs to control dreaded diseases. For sample, cis-platin and taxol are useful in cancer therapy. AZT (Azitothymidine) is used for AIDS victims.
• Some other categories of medicines synthesized are:

(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:

• Proper utilization of the fossil fuels - coal and petroleum by understanding its properties. For example, chemistry helps to measure the standard rating- octane number of engine or aviation fuel.
• Exploitation of alternate sources of energy like solar and nuclear, etc. Chemistry helped to synthesize uranium hexafluoride making possible for the enrichment of nuclear fuel U-235. Semiconductor materials like gallium arsenide, silicon, etc. are used in making solar panels.

Environmental Science

Environmental changes and chemistry are inextricably linked.

• Chemistry can explain the origin and impacts of phenomena such as air pollution, ozone layer depletion, and global warming.
• Chemistry can help in finding substitution and replacement of gases and products causing above effects. For example, like helping in replacing the refrigerants like chlorofluorocarbons (CFCs) with other environment-friendly products, etc.

Biology and Biotechnology

Chemistry has helped

• in the discovery of the DNA’s molecular structure and many of its roles in heredity. This has resulted in major advances in biology and biotechnology.
• to understand biotech processes like fermentation used to produce different liquor industry products (wine, beer, etc.), various antibiotics (e.g. penicillin), antibodies, therapeutic proteins, food products (e.g. cheese, curd, bread, etc.), enzymes and others.

Geology

In geology, chemical techniques are mostly required:

• To be used to analyze and identify rock samples in order to locate new mineral or oil deposits.
• To explain the formation of certain minerals, such as hematite, etc.

Oceanography

In Oceanography, chemistry is mostly used to:

• To track ocean currents
• Determine the flux of nutrients into the sea, and measure the rate of exchange of nutrients between ocean layers.

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:

• Bronze and copper items generally corrode due to oxidation. Electrolytic reduction is used to restore these antiquities.
• Carbon dating is one of the most widely used methods for the detection of the age of the old artifacts or fossils.

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;

• According to its physical state
• According to its chemical composition

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:

• Vapour pressure: A Liquid when kept in a closed container vaporizes into the free space above it. The process of vaporization will continue till the equilibrium is reached between liquid and vapor. The pressure at which the liquid and vapour can co-exist is called the vapour pressure of the liquid at a given temperature.
• Surface tension: The surface of a liquid is always in a state of tension because a molecule at the surface is attracted towards the bulk by a force much greater than that drawing it toward the vapor where the attracting molecules are more widely spread. The spherical shape of liquid bubble and capillary movement can be explained with the help of surface tension.
• Viscosity: It determines the flow of the liquid. It is the internal friction between layers of the liquid.

Gases

Gas is the third state of the matter. Gases have three characteristic properties:

• they are easy to compress
• they expand to fill their containers, and
• they occupy far more space than the liquids or solids from which they form.

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:

• adding thermal energy, i.e. heat to liquid water causes it to become steam or vapour,e. a gas.
• taking away energy also causes physical change, such as when liquid water becomes ice, i.e., a solid, when heat is removed.

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.

• At the melting point the solid and liquid phases exist in equilibrium. If we continue to apply heat to the sample, the temperature will not rise above the melting point until the entire sample has been liquefied.
• The heat energy, called latent heat of fusion, is being used to convert the solid into the liquid form.

Science in Acton

• A solid mixture, such as am metal alloy, can often be separated into its constituent parts by heating the mixture and extracting the liquids as they reach their different melting points.

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

• The best known of these substances is $C{{O}_{2}}$ or “dry ice” which sublime to gas.
• Other common substances which sublime are ammonium nitrate, camphor, anthracene, iodine and naphthalene.

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.

• Boiling point is dependent upon the pressure the substance is subjected to.
• A liquid under higher pressure will require more heat before vapour bubbles can form within it.

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

• Pure substances (or simply known as substance) are those matter that has distinct properties and a composition that does not vary from sample to sample. Water and ordinary table salt are examples of pure substances
• Mixtures are combinations of two or more substances in which each substance retains its own chemical identity. The substances making up a mixture are called components of the mixture.

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

• Diagnostic laboratories for blood and urine tests.
• Dairies and home to separate butter from cream.
• Washing machines to squeeze water from wet clothes.

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:

• Separation of acetone and water.
• Distillation of alcohol.

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

• Different fractions from crude oil.
• A mixture of methanol and ethanol.
• Different gases from liquid air.

 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:

• Column Chromatography,
• Thin Layer Chromatography (TLC)
• Paper Chromatography
• Gas Chromatography.

Paper Chromatography is one of the important chromatographic methods.

Applications: To separate

• Colours in a dye.
• Pigments from natural colors.
• Drugs from blood.

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

• On the other hand, molality is independent of temperature.

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:

• Vapour-pressure lowering
• Boiling-point elevation
• Freezing-point depression
• Osmotic pressure

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:

• Suspension: Materials of smaller particle size, insoluble in a solvent but visible to naked eyes, form suspension. The size of particles in suspension is over 1000 nanometers (nm).

• Colloid: A colloid contains smaller particles ranging in size from 1 to 1000 nanometers (nm).In case of true solutions the size of the particles are less than 1 nm.

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.

• The substance being dispersed is referred to as being in the dispersed phase,
• The substance in which it is dispersed is in the continuous phase is called dispersion phase.

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.

• Tyndall Effect: When light is shined through a true solution, the light passes cleanly through the solution, however when light is passed through a colloidal solution, the substance in the dispersed phases scatters the light in all directions, making it readily seen. An example of this is shining a flashlight into fog. The beam of light can be easily seen because the fog is a colloid. Blue colour of the sky and sea water, twinkling of stars, etc. are also examples of Tyndall effect.
• Dialysis: The substance is allowed to pass through a semi permeable membrane. The larger dispersed particles in a colloid would be unable to pass through the membrane; while the surrounding liquid molecules can .This process is known as dialysis.

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

• Suspensions have many applications in medical sciences.

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

• It is a temporary change.
• No new substances are formed.
• No change in mass takes place.
• Can be reversed by reversing the conditions.
• Change in physical state, size and appearance.

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

• A chemical change is permanent change and cannot be reversed to give back the original substance.
• One or more new substances (called products) are formed.
• Change in mass of a substance takes place.
• The composition of the product is different from that of the starting substance.
• A chemical change is always accompanied by the change in energy.

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:

• Hydrolysis- chemical reaction when combined with water
• Oxidation- it is a reaction with oxygen
• Carbonation- It is mixing of water with $C{{O}_{2}}$to make carbonic acid. This type of weathering is important in the formation of caves.
• Dissolution (also called leaching): it is the process by which rocks are dissolved when exposed to rainwater.

(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)

#### Other Topics

##### Notes - Chemistry, Matter and its Composition

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