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Wednesday, August 12, 2020

Notes of metals and non metal class 8/CBSE/ class 9/ by pathfinder coaching/suraj sir/best explanation

NOTES OF

METALS AND NON METALS

by Path Finder Coaching

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Introduction

Everything around us is categorized into either metals or non-metals. Hence, it is important to know what non-metals and metals are and how to distinguish them. The class 8 science chapter 4 discusses the various physical and chemical properties of metals and non-metals. To help you with it, here we list a few physical and chemical properties of metals and non-metals.

Metals

Metals are described as chemical elements that readily lose valence electrons to form positive ions (cations).
Examples: Aluminium, copper, iron, tin, gold.
Around 90 of the total 118 elements are metals.

Physical Properties

Physical Properties of Nonmetals

Occur as solids, liquids, and gases at room temperature
Brittle
Non-malleable
Non-ductile
Non-sonorous
Bad conductors of heat and electricity

Exceptions in Physical Properties

Alkali metals (Na, K, Li) can be cut using a knife.
Mercury is a liquid metal.
Lead and mercury are poor conductors of heat.
Mercury expands significantly for the slightest change in temperature.
Gallium and cesium have a very low melting point
Iodine is non-metal but it has lustre.
Graphite conducts electricity.
Diamond conducts heat and has a very high melting point.

Physical Properties of Metals

● Hard and have a high tensile strength
● Solids at room temperature, except mercury, which is liquid at room temperature.
● Sonorous
● Good conductors of heat and electricity
● Malleable, i.e., can be beaten into thin sheets
● Ductile, i.e., can be drawn into thin wires
● High melting and boiling points (except Cesium (Cs) and Gallium (Ga))
● Dense, (except alkali metals). Osmium – highest density and lithium – least density
● Lustrous
● Silver-grey in colour, (except gold and copper)

Non-Metals

Non-metals are those elements, which do not exhibit the properties of metals.
Examples: Carbon, Boron etc.

Chemical Properties of Metals

● Alkali metals (Li, Na, K, etc) react vigorously with water and oxygen or air.
● Mg reacts with hot water.
● Al, Fe, and Zn react with steam.
● Cu, Ag, Pt, Au do not react with water or dilute acids.

Chemical Properties

Displacement Reactions

A more reactive element displaces a less reactive element from its compound or solution.
i)

Z n (s) + C u S O_{4} (a q) \to Z n S O_{4} (a q) + C u (s)

ii)

2 A l (s) + F e_{2} O_{3} (m o l t e n) \to A l_{2} O_{3} (s) + 2 F e (m o l t e n)

Metals Reaction with Oxygen (Burnt in Air)

Metal + Oxygen → Metal oxide (basic)
● Na and K are kept immersed in kerosene oil as they react vigorously with air and catch fire.

4 K (s) + O_{2} (g) \to 2 K_{2} O (s)

(vigorous reaction)
● Mg, Al, Zn, Pb react slowly with air and form a protective layer that prevents corrosion.

2 M g (s) + O_{2} (g) \to 2 M g O (s)

(Mg burns with a white dazzling light)

4 A l (s) + 3 O_{2} (g) \to 2 A l_{2} O_{3} (s)

● Silver, platinum, and gold don’t burn or react with air.

Basic Oxides of Metals

Some metallic oxides get dissolved in water and form alkalis. Their aqueous solution turns red litmus blue.

$N a_{2} O (s) + H_{2} O (l) \to 2 N a O H (a q)$
$K_{2} O (s) + H_{2} O (l) \to 2 K O H (a q)$

Amphoteric Oxides of Metals

Amphoteric oxides are metal oxides which react with both acids as well as bases to form salt and water.
For example –

A l_{2} O_{3}, Z n O, P b O, S n O

A l_{2} O_{3} (s) + 6 H C l (a q) \to 2 A l C l_{3} (a q) + 3 H_{2} O (l)

A l_{2} O_{3} (s) + 2 N a O H (a q) \to 2 N a A l O_{2} (a q) + H_{2} O (l)

Z n O (s) + 2 H C l (a q) \to Z n C l_{2} (a q) + H_{2} O (l)

Z n O (s) + 2 N a O H (a q) \to N a_{2} Z n O_{2} (a q) + H_{2} O (l)

Reactivity Series

The below table illustrates the reactivity of metals from high order to low order.

Symbol	Element
K	Potassium ( Highly Active Metal)
Ba	Barium
Ca	Calcium
Na	Sodium
Mg	Magnesium
Al	Aluminium
Zn	Zinc
Fe	Iron
Ni	Nickel
Sn	Tin
Pb	Lead
H	Hydrogen
Cu	Copper
Hg	Mercury
Ag	Silver
Au	Gold
Pt	Platinum

Reaction of Metals with Water/Steam

$M e t a l + W a t e r \to M e t a l h y d r o x i d e o r M e t a l o x i d e + H y d r o g e n$

$2 N a + 2 H_{2} O (c o l d) \to 2 N a O H + H_{2} + h e a t$
$C a + 2 H_{2} O (c o l d) \to C a (O H)_{2} + H_{2}$
$M g + 2 H_{2} O (h o t) \to M g (O H)_{2} + H_{2}$
$2 A l + 3 H_{2} O (s t e a m) \to A l_{2} O_{3} + 3 H_{2}$
$Z n + H_{2} O (s t e a m) \to Z n O + H_{2}$

Reaction of Metals with Acid

Metals, which are reactive than hydrogen displace hydrogen from its dilute acids and produce respective metal salts and hydrogen gas.
Example: $M e t a l + d i l u t e a c i d \to S a l t + H y d r o g e n g a s$
$2 N a (s) + 2 H C l (d i l u t e) \to 2 N a C l (a q) + H_{2} (g)$
$2 K (s) + H_{2} S O_{4} (d i l u t e) \to K_{2} S O_{4} (a q) + H_{2} (g)$
Metals, which are less reactive than hydrogen cannot displace hydrogen from its acids and hence no reaction takes place.

How Do Metals React with Solution of Other Metal Salts

High reactive metal displaces the low reactive metal from its salt solution.

$M e t a l A + S a l t o f m e t a l B \to S a l t o f m e t a l A + M e t a l B$

F e (s) + C u S O_{4} (a q) \to F e S O_{4} (a q) + C u (s)

Reaction of Metals with Bases

B a s e + m e t a l \to s a l t + h y d r o g e n

2 N a O H (a q) + Z n (s) \to N a_{2} Z n O_{2} (a q) + H_{2} (g)

, when zinc reacts with aqueous sodium hydroxide it gives sodium zincate and hydrogen gas.

The Why Questions

Electronic Configuration

Electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.

Group 1 elements – Alkali metals

Element	Electronic configuration
Lithium (Li)	2,1
Sodium (Na)	2,8,1
Potassium (K)	2,8,8,1
Rubidium (Rb)	2,8,18,8,1

Group 2 elements – Alkaline earth metals

Element	Electronic configuration
Beryllium (Be)	2,2
Magnesium (Mg)	2,8,2
Calcium (Ca)	2,8,8,2
Stronium (Sr)	2,8,18,8,2

How Do Metals and Non-metals React

Metals lose valence electron(s) and form cations.
Non-metals gain those electrons in their valence shell and form anions.
The cation and the anion are attracted to each other by strong electrostatic force, thus forming an ionic bond.
For example: In Calcium chloride, the ionic bond is formed by oppositely charged calcium and chloride ions.
Calcium atom loses 2 electrons and attains the electronic configuration of the nearest noble gas (Ar). By doing so, it gains a net charge of +2.

The two Chlorine atoms take one electron each, thus gaining a charge of -1 (each) and attain the electronic configuration of the nearest noble gas (Ar).

Ionic Compounds

Ionic compounds are chemical compounds in which oppositely charged ions are held together by electrostatic forces called ionic bonds.
An ionic compound always contains an equal magnitude of positive and negative charges. For example: $C a C l_{2}$ , $N a C l$ , $K_{2} S O_{4}$ , etc

Properties of Ionic Compounds

Are usually crystalline solids (made of ions).
Have high melting and boiling points.
Conduct electricity when in aqueous solution or molten in water and when melted.
Are mostly soluble in water and polar solvents.

Physical Properties of Ionic Compounds

Ionic compounds are solids and are hard to break, due to the presence of the strong force of attraction between the positive and negative ions.
They generally break into pieces when pressure is applied, hence are considered brittle.

Lattice Structure of Ionic Compounds

A lattice is a regular arrangement of particles, whether these are atoms, ions or molecules.
Ionic solids usually exist in regular, well-defined crystal structures.

Electric Conduction of Ionic Compounds

Ionic compounds conduct electricity in the molten or aqueous state when ions become free and act as charge carriers.
In solid form, ions are strongly held by electrostatic forces of attractions and not free to move; hence do not conduct electricity.

For example, ionic compounds such as NaCl does not conduct electricity when solid conduct electricity but when dissolved in water or in molten state, it will conduct electricity.
Metals and Non Metals 04

Melting and Boiling Points of Ionic Compounds

In ionic compounds, the strong electrostatic forces between ions require a high amount of energy to break. Thus, the melting point and boiling point of an ionic compound are usually very high.

Solubility of Ionic Compound

Ionic compounds are generally soluble in polar solvents such as water ,whereas the solubility tends to decrease in non-polar solvents such as chloroform, oil, etc.

Extraction of Metals and Non-Metals

Applications of Metals and Non-metals

Zinc is used to protect the iron from rusting.
Gold and silver are used for making jewellery.
Oxygen is used by plants and animals.
For the preparation of ammonia, nitric acid and fertilizers, nitrogen is used.
For the purification of water, chlorine is used.
Diamonds are used for cutting glass in different industries.

Occurrence of Metals

Most of the elements especially metals occur in nature in the combined state with other elements. All these compounds of metals are known as minerals. But out of them, only a few are viable sources of that metal. Such sources are called ores.
Au, Pt – exist in the native or free state.

Extraction of Metals

Roasting

Roasting:- Converts sulfide ores into metal oxides on heating strongly in the presence of excess air.
It also removes volatile impurities.

2 Z n S (s) + 3 O_{2} (g) + H e a t \to 2 Z n O (s) + 2 S O_{2} (g)

Calcination

Calcination: Converts carbonate and hydrated ores into oxides on heating strongly in the presence of limited air. It also removes volatile impurities.

Z n C O_{3} (s) + h e a t \to Z n O (s) + C O_{2} (g)

C a C O_{3} (s) + h e a t \to C a O (s) + C O_{2} (g)

Extraction of Metals, Which Are Lower in the Reactivity Series

The metals like gold, silver, platinum, and copper are the least reactive and found in free state.
Copper and silver are also found in the combined state as their sulphide or oxide ores. These metals usually occur as sulphide ores, which further undergo roasting.

Extraction of Metals, Which Are Mid-Way in the Reactivity Series

The metals such as Zn, Fe, Pb, etc are moderately reactive and usually present as oxides, sulphides or carbonates in nature.
The carbonate and sulphide ores are subjected to calcination and roasting respectively, followed by reduction of metal oxides to obtain the metals.

Extraction of Metals, Which Are on the Top of the Reactivity Series

Na, Ca, Mg, Al, etc., cannot be obtained by reducing with C due to high affinity for oxygen.
These metals are obtained by electrolytic reduction or electrolysis of their oxides, hydroxides or chlorides in the molten state.

Enrichment of Ores

It means removal of impurities or gangue from ore, through various physical and chemical processes. The technique used for a particular ore depends on the difference in the properties of the ore and the gangue.

Refining of Metals

Refining of metals – removing impurities or gangue from crude metal. It is the last step in metallurgy and is based on the difference between the properties of metal and the gangue.

Electrolytic Refining

The process of purifying impure metal to obtain pure metal on the passage of electric current is called electrolytic refining.
Metals like copper, zinc, nickel, silver, tin, gold etc., are refined electrolytically.
Anode – impure or crude metal
Cathode – a thin strip of pure metal
Electrolyte – aqueous solution of a metal salt From anode (oxidation) – metal ions are released into the solution
At cathode (reduction) – equivalent amount of metal from solution is deposited
Impurities deposit at the bottom of the anode.

Friday, July 24, 2020

NOTES OF FIBRE TO FABRIC / SYNTHETIC MATERIALS /BEST NOTE

SYNTHETIC MATERIALS

Fibres and FabricsThe clothes are made of fabrics. Fabrics are made from fibres obtained from natural or artificial sources.

Types of Fibres:1. Natural fibres: These are obtained from natural sources, called natural resources. Examples: cotton, silk, wool, etc.

2. Synthetic fibres: These are man-made are called man-made or synthetic fibres. Examples: rayon, nylon, acrylic, etc.
(i) Synthetic fibres are made of small units of chemicals joined together in the form of large chain. The formed chain is called polymer.
(ii) Polymer is a Greek word in which ‘poly’ means many and ‘mer’ means units. So, a polymer is made of many repeating units.
(iii) Polymers occur in nature also. Example: Cotton is a polymer called cellulose. Cellulose is made up of a large number of glucose units.

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Types of Synthetic Fibres:
1. Rayon:
(i) Fibre is obtained by chemical treatment of wood pulp. This fibre is called rayon or artificial silk.(ii) Rayon fibre can be made in different colours by dyed. Rayon is very cheap compared to silk.
(iii) Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets.

2. Nylon:
(i) Nylon is man-made fibre. It was first fully synthesized fibre. The production of nylon was started without using any natural raw material (from plant or animal) almost simultaneously in New York and London, thus it got its name (NY for New York and Lon for London) as nylon. It is synthesized from coal, water and air. Cloths from nylon are very strong elastic and light lustrous and easy to wash.
(ii) Firstly nylon was used in making bristle of toothbrush commercially. After that, it was used for making fabrics.
(iii) Nylon is used for making clothes, ropes, socks, curtains, sleeping bags, parachutes, etc. The nylon fibre is stronger than a steel wire.

3. Polyester:
(i) Polyester (Poly + ester) is made up of the repeating units of a chemical called an ester.
(ii) Polyester is a man made or synthetic fibre. Fabric made from this fibre does not get wrinkled easily, remains crisp and easy to wash. Example: shirts, pants, jacket, bed sheets, curtains, sarees, mouse-pad, etc.
(iii) Polyester is used to make ropes, fabrics for conveyor belt, cushioning and insulating material in pillow, etc.
(iv) Terrycot is made by mixing of two types of fibres terylene and cotton. Polycot, polywool, etc. are other fabrics are made by the mixing of polyester with other natural fibres.
(v) PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

4. Acrylic:
(i) Acrylic is man-made or synthetic fibre. Acrylic resembles wool. It is also called as artificial wool or synthetic wool. Acrylic is cheaper than natural wool and can be made in various colours by dyeing.(ii) Clothes are made from acrylic are relatively cheaper than cloths are made by wool.
(iii) Acrylic is used in making sweaters, blanket, and other many clothes.

Characteristics of Synthetic Fibres:
(i) Synthetic fibres are cheaper, stronger and durable than natural fibre.
(ii) It is easy to maintain, easy to wash, dry up in less time and readily available.
(iii) Synthetic fibres possess unique characteristics which make them popular dress materials.

Plastics:(i) Plastic is also a polymer like the synthetic fibre. All plastics do not have the same arrangement of units. In some it is formed in linear, whereas in others it is formed cross-linked.

Plastic is easily mouldable in all types of possible shapes. Plastic can be recycled, coloured, reused, rolled into sheets or made into wires.

(i) Plastic is used in making toys, suitcase, bags, cabinets, brush, chairs, tables, and many other countless items.

(ii) Polythene (Poly + ethene) is one of the most famous examples of plastic, which is used in manufacturing of carry bags.

Types of Plastic:Plastic can be divided into two main types – Thermoplastics and Thermosetting.

1. Thermoplastic:
(i) Such plastics which get easily bent or deform on heating are known as thermoplastic.Examples of thermoplastics are PVC and Polythene.
(ii) It is used in making toys, bottles, combs, containers, etc.

2. Thermosetting plastic:
(i) Such plastics which when mould once, cannot be softened or deformed by heating. These are called thermosetting plastics. Examples of thermosetting plastics are Bakelite and melamine.
(ii) These plastics are used in making hard board, electric switch, handles of electrical appliances, handles of kitchen utensils, floor tiles, etc.
(iii) Melamine is versatile material and poor conductor of heat. It resists fire, thus it is used in making floor tiles, kitchen materials, fabrics which resist fire.
(iv) Bakelite is poor conductor of electricity and heat, thus it is used for making electrical switches, handles of various utensils and other electrical appliances.

Plastic as a material of choice:Plastic has light weight, lower price, good strength and easy handling. Being lighter as compared to metals, plastics are used in cars, aircrafts and spacecrafts, too.

Characteristic properties of plastics:
1. Plastic is non-reactive:
(i) Plastics do not react with water and air that’s whyit does not get rusted like iron. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.
(ii) Due to this property of plastic, it is suitable for making of container, water tank, water bottle, plastic pipes, taps, chair, table and other many types of furniture.

2. Plastic is light, strong and durable:
(i) Plastics are light weight, durable, cheap, very strong and can be moulded into different shapes and sizes.
(ii) Due to this property of plastic, it is very much in need today. It is used for various purposes like polythene bags or pencil box, water bottle or umbrella, furniture or air craft, the use of plastic can be seen everywhere.

3. Plastics are poor conductors:
(i) Plastics are poor conductor of heat and electricity.
(ii) Due to this property of plastics, it is suitable to make the insulating covering of electric wires, handles of electrical appliances, handles of utensils, handles of screw drivers, kitchenware, floor tiles, etc.

Some Uses of Plastic in Various Fields:
(i) Plastics find extensive use in the health-care industry. Plastics are used for the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.
(ii) Special plastic cookware is used in microwave ovens for cooking food without affecting the plastic vessel.
(iii) Teflon is a special plastic on which oil and water do not stick. It is used for making non-stick coating on cook wares.
(iv) Fire-proof plastics: Synthetic fibre catches fire easily. The uniforms of firemen have coating of melamine plastic to make them flame resistant.

Biodegradable and Non-biodegradable:

1. Biodegradable:A substance which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. Examples: peels of vegetables, food stuffs, fruit, paper, cotton cloths, wood, etc.

2. Non-biodegradable:A substance which is not easily decomposed or takes many years to get decomposed by natural processes is termed as non-biodegradable. Examples: tin, aluminium, plastics, etc.

Plastics and the Environment:
(i) Plastic is a non-biodegradable material. It takes many years to get decomposed or either does not get decomposed.
(ii) Due to non-biodegradable property of plastic, it is a very major problem for environment.

Problem:
(i) Now days, plastic is very popular and used it for many purposes. As a result, we generate a large amount of plastic waste. Since plastic has non-biodegradable property, so plastic waste is getting accumulated in the environment. It causes environmental pollution.
(ii) Accumulated plastic waste is a major concern as it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution.

Preventive measures:
(i) We should avoid the use of plastics things as far as possible.
(ii) Do not throw plastic bags in the water bodies or on the road.
(iii) The biodegradable and non biodegradable wastes should be collected separately and disposed off separately.

For dealing with plastic waste, we should follow the three Rs, i.e. Reduce, Reuse and Recycle.

1. Reduce:We should reduce the use of plastic. Examples: We should use cloth or jute bag for purchasing any things instead of using plastic bags.

2. Reuse: We should reuse some plastic things and containers in our homes and offices, For example: Empty plastic bottles and container should be used for keeping other items in the home and kitchen.

3. Recycle:Thermoplastic can be recycled. So, items made of thermoplastic should be sent to the recycling industry. Examples: Toys, buckets, mugs etc.

मृत सागर : एक अनोखा सागर /Dead sea / जहां कोई नहीं डूबता/ share if you liked it

मृत सागर : एक अनोखा सागर, जहां कोई नहीं डूबता 'डेड सी' और 'अरबी झील' के नाम से मशहूर जॉर्डन, इजराइल और फिलीस्तीन के बीच में मौजूद है यह मृत सागर!

इसको 'डेड सी' और 'अरबी झील' के नाम से भी जाना जाता हैं. इसके साथ ही मृत सागर समुद्र के तल से लगभग 400 मीटर नीचे दुनिया का सबसे निचला बिंदु है. इसकी लम्बाई करीब 65 किलोमीटर और चौड़ाई 8 किलोमीटर है.

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मृत सागर का पानी दुनिया के दूसरे जलस्रोतो से अधिक खारा है. इसमें मौजूद नमक औसतन एक घन फुट के लिए एक किलोग्राम होता है, लेकिन इसका पानी दूसरे समुद्रों से लगभग 6-7 गुना ज्यादा खारा होता है.

इसकी दूसरी बड़ी खासियत यह है कि इस सागर का पानी अपने खारेपन की वजह से ज्यादा भारी होता है. इस कारण इसका पानी ऊपर से नीचे की ओर बढ़ता है. परिणाम स्वरूप यह सागर अपने उच्च घनत्व के लिए जाना जाता है. यही वजह है कि इस सागर में किसी भी इंसान का डूबना असंभव है.

अपनी इन्हीं अद्भुत खूबियों के कारण हमेशा से ही सैलानियों के लिए यह आकर्षण का केंद्र बना हुआ है.

सैलानी इसके अद्भुत नज़ारों को देखने और इसकी खासियत से रूबरू होने जाते हैं. गजब की बात तो यह है कि इंसान तैरना भी नहीं जानता, वो भी इस सागर में आसानी से लेट कर पिकनिक मना सकता है.

बताते चलें कि 2007 में इसका नाम विश्व के सात (7 न्यू वंडर्स इन द वर्ल्ड) अजूबों की लिस्ट के लिए चयनित किया गया था. वह तो इसके पक्ष में ज्यादा वोटिंग नहीं हुई. इस कारण वह दुनिया के सात अजूबों में शामिल नहीं हो सका.

Tuesday, July 21, 2020

Notes of polygon and all formula of class 8 full notes with best explanation

Notes of polygon (best explanation)

A plane shape (two-dimensional) with straight sides.

Examples: triangles, rectangles and pentagons.

(Note: a circle is not a polygon because it has a curved side)

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an area enclosed by line segments only is called polygon

Types of polygons:

On basis of sides ,POLYGONS are of two types

1.REGULAR POLYGONS

2.IRREGULAR POLYGONS

1.Regular polygon: a polygon is said to be regular if its all sides are equal

2.Irregular polygons: a polygon is said to be irregular if its all sides are not equal

please note that the names of polygons are bases on the number of sides present in them

examples of polygons:-

polygons number of sides

1.triangle 3 sides

2.quadrilateral 4 sides

3.pentagon 5 sides

4.hexagon 6 sides

5.heptagon 7 sides

6.octagon 8 sides

7.nonagon 9 sides

8.decagon 10 sides

If all sides of triangle are equal then it is called Equilateral triangle
If all sides of quadrilateral are equal then it is called Square

On the basis of Angles :-

Polygons are of two types:

1.Concave polygon: Polygons having at least one interior angle more than 180 degree are called Concave polygons

2.Convex polygon: Polygons having each interior angle less than 180 degree are called Convex Polygons

The sum of all the exterior angles = 360°
Interior angle + corresponding exterior angle = 180°.
The sum of the interior angles of a convex POLYGON, having n sides is 180° (n - 2).
The sum of the exterior angles of a convex polygon, taken one at each vertex, is 360°.

The measure of an exterior angle of a regular n- sided polygon is
The measure of the interior angle of a regular n-sided polygon is
The number of diagonals of in an n-sided polygon is

Perimeter of a polygon: The perimeter of a polygon is the sum of the lengths of all its sides.

Area of a polygon: The region enclosed within a figure is called its area.

Diagonal of a polygon: The segment joining any two non-consecutive vertices is called a diagonal.

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