Science and technology

Understanding Matter

2.1 Matter 2.2 Elements 2.3 Compounds 2.4 Mixtures 2.5 Types of mixtures 2.6 Solutions, suspension and colloidal solutions

Matter is composed of tiny particles Most of the matter around us exists as mixtures of two or more substances. Example : Sodium chloride is made up of Sodium and Chlorine. A pure substance consists of a single type of Particles. Example : Each and every particle of Nitrogen is made up of Nitrogen itself.

Pure substances are further classified into elements and compounds. An elements is the type of matter composed of only one kind of subtances An element cannot be further subdivided into simpler substances by any physical and chemical means. Today, 119 elements are known; out of which 92 are found in nature.

They are further classified into An element can be represented by using a symbol. You already know that the symbol of Hydrogen is H. The molecular of Hydrogen consists of two hydrogen atoms. Hence the molecular formula of Hydrogen is written as H2. ELEMENTS They are further classified into METALS NON-METALS METALLOIDS

Table Elements Lustre Solid/liquid/gas Hard Brittle Ductile Malleable Conductor of electricity Copper Yes Solid No Iron Silver Sulphur Nitrogen gas Silicon Germanium

METALS NON-METALS METALLOIDS They are generally solids with characteristics such as hardness, malleability, Ductility, lustre and ability to conduct heat and electricity. Example : Copper, Iron, Silver etc. NON-METALS They are generally non-lustrous, brittle, poor conductors of heat and electricity. Example : Sulphur, Nitrogen etc. METALLOIDS Metalloids have characteristics common to metals and non-metals. Example : Arsenic, Silicon, Selenium etc.

COMPOUNDS A compound is the substance made up of two of more types of elements chemically combined in a fixed proportion A compound can be further subdivided into simpler substances by only chemical means. An example of a compound is water. It is a compound that contains the elements hydrogen and oxygen whose atoms are combined in the ratio 2 : 1. A compound has totally new properties then the constituents. The chemical formula H2O represents the compound of water. Water has different properties than Hydrogen and Oxygen.

Compound Molecular formula 1. Water H2O 2. Aluminium oxide Al2O3 3. Potassium permanganate KMnO4 4. Copper Sulphate CuSO4 5. Potassium dichromate K2Cr2O7 6. Calcium hydroxide Ca(OH)2 7. Sodium bicarbonate NaHCO3 8. Sodium carbonate Na2CO3 9. Benzene C6H6 10. Hydrogen sulphate H2SO4

MIXTURES A mixture is a substances which is obtained by mixing two or more substances in any proportion. The constituents of a mixture retain their original properties. The mixture can be further subdivided into simpler substances by simple physical processes like holding the magnet, handpicking etc. 3. In a mixture, the constituents are not in a fixed proportion.

Alloys When two or more metals or a metal and a non metal are fused together than, it is an alloy. Example : Stainless steel is an alloy of iron, carbon, chromium and nickel. Carbon gives hardness to the mixture. Chromium and nickel give a silvery look to the mixture. In air there are mainly Nitrogen and Oxygen along with other gases. These gases retain their original properties. They do not chemically combine with each other on their own. Air is also a mixture.

TYPES OF MIXTURES Homogeneous mixture Heterogeneous mixture Homogeneous mixture: The constituents of a homogeneous mixture are uniformly mixed throughout the mixture. The properties and composition of a homogeneous mixtures are the same throughout the mixture. Example : Potassium Permanganate solution is a homogeneous mixtures. Heterogeneous mixture : The constituents of a heterogeneous mixture are not uniformly mixed throughout the mixture. The properties and composition of a heterogeneous mixtures are not the same throughout the mixture. Example : A mixture of water and oil is heterogeneous in nature.

SOLUTION, SUSPENSION AND COLLOIDAL SOLUTION Solution A solution is a homogeneous mixture of two or more substances. Lemonade, soda, water are some of the examples of solution. There are solid solutions (Alloys) and gaseous (air) also. The particles in a solution are very small size, they do not scatter a beam of light passing through it.

Types of Solution Types of solutions Examples Gas in liquid Oxygen in water. Liquid in liquid Alcoholic beverages are basically solutions of ethanol in in water. Solid in liquid Sugar or salt in water. Gas in solid Sponge Liquid in solid Mercury in gold, forming an amalgam. Solid in solid Alloys like steel, bronze and many others.

Suspension Colloidal mixture The substances which dissolves is called the solute. The substances in which solute dissolves is solvent. In solutions the proportion of solute is less than that of solvent. Suspension A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended in it. These particles are visible to the naked eye. Colloidal mixture A colloid is a mixture where the size of the particles is less than the size of particles in a suspension.

Due to the relatively smaller size of the colloidal , as compared to the suspension, the colloidal mixture appears to be homogeneous. But a colloid mixture is a heterogeneous mixture. The two components of a colloid are the dispersed phase and dispersed medium E.g. milk. John Tyndall Here milk is the dispersed phase and water is the dispersion medium. Here both the dispersed phase and dispersion medium are liquids. We cannot see colloidal particles with naked eyes. These small particles can easily scatter the beam of light. The scattering of beam of light is the Tyndall Effect. (Named after the scientist )

Tyndall Effect The tyndall Effect is caused by scattering of light by very small particles in colloidal solutions in a transparent medium. It is often observed from the dust in the air when sunlight comes in through a window, or comes down through holes in clouds. It is observed when headlight beams are visible on foggy nights.

SEPARATING COMPONENTS OF A MIXTURE Heterogeneous mixture can be easily separated by simple means like hand picking, filtration and other physical means. Evaporation is another technique used for separating mixtures. For some mixtures, one needs techniques like distillation and crystallization to separate them. Fractional distillation is another method where a mixture of liquids is separated into components according to their different boiling points. This method is also used for separate components of air.

Created by :- Mrs. Choudhari p.p. Std :- 9tH

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