Class 7 Chemistry CBSE

(1)

• General Chemistry

Concept Maps

Class VII

• Sorting Materials In Groups

• Physical and Chemical Change

• Acids, Bases and Salts

Chemistry

• Fibre To Fabric

• Air

• Separation of Substancs

• Water A Precious Resources

• Waste Water Story

(2)

Spandex (Lycra)

FIBRES

Semi synthetic

Synthetic

Formation

Koroseal

Polyester (terylene or mylar or dacron) 1. Absorbs less water

2. Strong , light,elastic and resists wrinkles

Sweaters, socks High elasticity and stretchable Cotswool, polycot, terrywool

Natural

Blended

Acrylic

(Orlon or Acrilan)

Nylon Air and water proof

Light, elastic and high tensile strength

Rayon

(Artificial silk)

1. Absorbs moisture 2. Lustrous and resembles silk A thread or filament from which a cloth is made

Viscose process

Wool

Silk

Cotton

Properties Uses Rain coat, bathroom curtains Uses Properties Shirt, ties, lining etc. Properties Uses Swimming costumes caps, T-Shirts Uses Warm, soft and light Properties Uses Umbrellas, parachutes, socks Properties Properties Uses Magnetic recording tapes , video cassettes

curtains

(3)

SEPARATION OF

GASES FROM AIR

Removal of dust, gases & water vapour

CITY WATER

SUPPLY

Liquefaction

Purification

Fractional

distillation

Liquid N boils off followed by liquid O 2 2

Sterilization

Removal of harmful micro organism

Sedimentation

Heavy impurities settle down

Physical

change

Definition Example Characteristics

Filtration

CHANGES

Chemical

change

Suspended impurities separates Definition Example Characteristics

(4)

SEPARATION

TECHNIQUES

Distillation

Principle (Boiling point)

Fractional

distillation

Example (Alcohol/water)

Separating

funnel

Principle (Density) Example (Oil/Water)

Centrifugation

Principle (Density) Example (separation of cream from milk)

Sublimation

Principle

(Ability to sublime)

Example

(Sand/I )

2

Using Suitable

Solvent

Principle (Solubility) Example (Sugar/Sand)

Evaporation

Principle (Boiling point) Example (NaCl/Water)

Chromatography

Method

Principle (Relative solubility & affinity of

constituents) Example (Ink/water) Solvent Water Alcohol Adsorbent medium MgO Al O2 3 Filter paper Principle (Boiling point)

(5)

Acids

On the basis of concentration

Definition

Classification

Properties

Bases

Definition

Classification

Compounds which

when dissolve in water gives H /H O ions e.g. HCl, H SO + + 3 2 4 Compounds which when dissolve in water gives OH ions e.g. NaOH, NH OH4 On the basis of Source On the basis of strength

Dilute acid Concentrated

acid Mineral acids Organic acids Strong acids Weak acids On the basis of concentration

Dilute base Concentrated

base On the basis of strength Strong base Weak base

+

Neutralization Solution conduct electricity Soluble in water

Acids sour in taste bases bitter in taste

Acids turns blue litmus to red base turns red litmus to blue

Indicator

Olfactory Natural Artificial Methyl orange Phenolphthalein – HCOOH

Which indicates the nature of particular solution Substances whose odour changes in acidic or basic solutions a c i d Almost completely ionise (H SO , HCl)2 4 Partially ionise Partially ionise NH OH, Ca(OH)4 2 Almost completely ionise (NaOH, KOH) H O2

>

acid acid

>

H O2 H O2

>

base base

>

H O2 e.g. (H SO HCl)2 4, HCl + NaOH NaCl + H O + Heat2

(6)

FIBRE TO

FABRIC

1. Absorbs moisture 2. Lustrous and resembles silk

Cotton

• Shearing : The fleece of the sheep along with a

thin layer of skin is removed from its body.

Scouring :The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt

Sorting : Separation of hair of different textures

is called sorting

A thread like part in animal and vegetable tissues

Synthetic

or man made

Semi

Synthetic

Modified natural fibres

Rayon

(Artificial silk)

Nylon

Plant and animal fibres

Wool

Jute

Silk

Properties (Shiny) Uses (saris, jeckets , gloves, carpets)

(7)

WASTE WATER

STORY

Eutrophication

Biological

Oxygen demand

(BOD)

Waster water treatment

plant WWTP

Cleaning of

waste water

Consitutent

e.g.

• Pathogens such as

bacteria virus, parastic worms

• Soluble organic material such as

urea, proteins

• Gases such as H S, CO , CH

2 2 4

Treatment of waste water using

physical, chemicaland biological process

Major of the oxygen utilised by microorganisms

during oxidation of organic materials

Chemical

Oxygen demand

(COD)

Index of the waste of water which can

be oxidised by strong oxidising agents

The excessive growth of algae and aquatic

plants due to added nutrients

Sanitation &

disease

Poor sanitation and contaminated drinking

water is the cause of a large number of dieseases

Sewage disposal

Vermi-processing

toilet

Septic tanks, chemical

toilets, combusting pits

Humans excreta is treated

by earthworms

(8)

Water a precious

resources

Forms of

water

Availability

of water

Physical

properties

Chemical

properties

Depletion

water table

Water

cycle

Water management

proper use of water

Composition

of water

Solid e.g. ice Liquid e.g. H O2 (l) Gaseous e.g. water vapours

e.g. Oceans, rivers, lakes, ice caps

Element hydrogen & oxygen

Mass ratio hydrogen : oxygen 1 : 8 Melting point 0ºC Boiling point 100ºC Density 1 gm/cc Inert Action with litmus Action with metals

2K + 2H O(l)2 2KOH(aq) + H O(g)2

Increasing industries Increasing population

(9)

Other gases, carbon dioxide (0.03%) and water vapour Argon (0.934%) Nitrogen (78.084%) Oxygen (20.946%)

Uses

AIR

Components

Composition

Atmosphere

The transparent, thick and

invisible envelope of air surrounding us

Inert gases Dust Water vapour Oxygen CO2 Nitrogen He, Ne, Ar,

Kr, Xe

Birds , bats

can fly

Dispersal of

seeds

Sailing yachts

Wind mill

Moving air Exosphere Thermosphere Mesosphere Stratosphere Troposphere

(10)

CHANGES

IN MATTER

Physical changes Chemical changes Characterstics Defintion Example Defintion Example _{Characterstics}

Change that alters the physical properties of matter without changing the chemical composition

Change that alters the chemical properties of matter with changing the chemical composition

No new product

is formed _{No net gain or} loss of energy

Change is temporary and reversible No change in the

weight of substance

Change in the weight of new substance

Change is permanent and irreversible

New product is formed

Net gain or loss of energy

Corrosion

Rusting

Defination

Equation

Preventation

(Iron surface gets covered with a brown flaky substance)

1. Iron surface coating with thin layer of paint, varnish 2. Iron surface coating with

zinc (galvanization) 3. By alloying (Fe, Cr, Ni) 4Fe + xH O + 3O2 2 2Fe O .xH O2 3 2 Conditions 1. Presence of air 2. Presence of water Burning of Mg in air Burning of LPG Crystallisation

(Pure soluble substance seprates out in the form of crystals) Action of heat on iodine Switching on an electric bulb Dissolving of NaCl in water Burner Tripod stand Wire gauze Iron vessel Copper sulphate solution Sand Sand bath Dry Air Air Air Layer of oil Rusted nails Non-rusted

nails Non-rustednails

Anhydrous CaCl2

(A)

(Air and Water)

(C)

(Only dry air)

(B)

(Boiled distilled water)