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SORTING OF MATERIALS INTO, GROUPS, CLASS 6, SCIENCE

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Materials…., Materials Around Us, • When we look around, we find, ourselves surrounded by a, number of objects. Some of, these different objects are, made from a number of, different materials, while, others are made using the, same material., • For Example: Both desk and, chair are made from wood, while pen and dustbins are, made using plastic. The, material from which an object, is made depends on its, properties.

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Why do we need to group the, objects…, We need to group objects for a, number of reasons:, , • 1. To save time to find the, object., • 2. It saves our energy, • 3. Grouping or sorting makes, the place well arranged and, beautiful, • 4. Convenience to store: We, often group objects in order to, store similar objects together in, order to make locating them, easier in the future., • 5. Convenience to study: We also, group objects so that it becomes, easy for us to study their features, as well as the patterns.

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Material Grouping,  Material: - The matter from which an object is made, , is called material. E.g. glass, steel, wood ,leather etc.,  Classification:- The process of sorting and grouping, materials according to some basic similarity is called, classification. Object can be classified on different, basis. i.e. shape, material used, uses etc.,  Basis of grouping:- Material can be grouped on the, basis of similarity and differences in their property., Different types of material have different properties, such as appearance, solubility, transparency,, conductivityand behavior towards magnet etc., , www.reflectivelearn.com

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Properties of materials, • We choose to make an object depending on its, properties and the purpose for which the object, is to be used., So we should know some properties of materials:, • 1. Appearance, • 2. Hardness, • 3. Solubility, • 4. Density, • 5. Transparency

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Appearance, Lustre of Gold, , • Materials can be classified on the, basis of how they look or appear., Some materials have lustre,, which is a soft glow to them while, others are plain ordull ., • Materials that have such lustre, can usually be classified, as Metals. Examples include, gold, copper, aluminium, iron etc., • Usually, a metal loses its lustre, after some time due to the action, of moisture and air on it. This is, called Corrosion of metals., Therefore only freshly-cut metals, appear to have lustre on them.

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Hardness, • Materials can also be, classified on the basis of, hardness., • Materials that can be easily, compressed or scratched, are called Soft. Ex-cotton,, sponge, • Materials that cannot be, scratched and are difficult, to compress are termed, as Hard. Ex- iron, wood

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Metal Iron is Hard, Hardness

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Soluble and Insoluble, Soluble and Insoluble materials, •, •, •, , •, , Materials that can be dissolved in, water upon stirring are said to, be soluble materials., For Example, Sugar and Salt can be, dissolved in water., Materials that cannot be dissolved in, water no matter how much we stir, them are said to, be insoluble materials. For Example,, Stones and Clothes cannot be, dissolved in water., Not just solid materials, even liquids, have the property of being soluble or, insoluble. For Example, Lemon juice, can easily dissolve in water while oil, does not dissolve and deposits as a, thin layer on the uppermost layer of, water.

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Objects that can Sink and Float, DENSITY, • There are some insoluble, materials which sink to the, bottom of the surface when, put in water while some, other floats on water., • It is all because of Density, of a substance. Density is, defined as mass present in, per unit of volume of the, substance., , Understand the Concept, • Object with higher density, than water will sink. A coin is, made up of metal. Density of, metal is higher than water., That’s why coin sinks in water., • The objects with lesser, density than water will float, on water. For Ex: Leaves and, Corks float on water while, rocks and coins sink in water

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Objects that can Sink and Float, Tell the Answer:• The objects can Sink and, Float depending on their, density relative to water., • Answer the following:, • Will a needle float or sink?, • Will a plastic pen float or, sink in water?, • Will a pencil float or sink in, water?

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Transparency, Understand the Concept, •, , •, , •, , Objects or materials which can be seen, through are said to, be transparent objects., For Example, Glass, clear water and some, plastics can be seen through and are, hence transparent materials., Objects and materials through which, things can be seen but only partially are, called Translucent objects., For Example Butter paper and frosted, glass are some examples of translucent, objects., Objects which cannot be seen through, are known as opaque objects., For Example, Metals, wood and, cardboard are some examples of opaque, materials as you cannot see through, them.

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Transparency, Understand the Concept, •, , •, , •, , Objects or materials are transparent, because the light rays can easily pass, through them., Glass, clear water and some plastics can, be seen through because light can easily, pass through them., Objects or materials are translucent, because the light rays partially pass, through them., Butter paper and frosted glass allow the, light to partially pass through them., Objects or materials are opaque because, the light rays cannot pass through them., Metals, wood and cardboard are some, examples of opaque objects. No light can, pass through them so you cannot see, through them.

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Thank You, , THANK YOU