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Class 6 Science NCERT Part 2: Chapter 3-7 Presented by Dr. Roman Saini
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s Ch 3: Fibre to fabric Fibres: cotton, wool, silk or synthetic. Cotton, wool (rabbit, yak, camel, sheep, goat), silk (cocoon), jute: Natural fibres; Polyesters nylons: synthetic Loose thread-yarn-can be pulled. Thin strands in a single yarn-fibres. Spinning (making yarns from fibres using takli or charkha) Yarns into fabric-weaving (looms) and knitting Cotton bolls, burst, seeds with cotton fibres (machine or hand separation is called ginning of cotton bolls) Jute: Stem, West Bengal, Bihar, Assam, Bangladesh, stem immersed in water for few days, rotting of stem, fibres are separated
Clothing in ancient times: Leaves, twigs, Vines, animal fleece or hair were twisted together into long strands Flax in nile
Weaving Spinning . Fabric Fibres Yarns Knitting
-2. Ch 4: Sorting-materialinto groups 1 Objects 1 or many materials 1 material = many objects Grouping helps in systematic arrangement and better study, analysis etc. , Metals like aluminium, iron, copper have lustre (gentle sheen or soft glow), action lose it (rust etc.) of air and water Hard or soft - Mohs scale of mineral hardness (1 to 10 - talc to diamond, scratch) (8) topaz; and (9) corundum (10) Diamond s (1) talc; (2) gypsum; (3) calcite; (4) fluorite; (5) apatite; (6) orthoclase; (7) quartz; Soluble or insoluble; Transparent or translucent
Ch 5: Separation of substances Make it fitter, purer for use; handpicking for slightly larger impurities, separate grain from stalks etc. threshing; using wind for separation winnowing (heavy grain particles falls, lighter particles are blown away), sieving: passing of smaller particles though minute holes while retention of larger particles Sedimentation: When the heavier component in a mixture settles (followed by water addition), Decantation: Removal of water and impurities, Filtration: Passing though strainer, filter should have pores smaller than impurities. Evaporation: Water into vapour, happens at all the temperatures continuously, wherever water is present
Process of conversion of vapour into its liquid form is called condensation When no more solute can dissolve in a solution, it is saturated(saturation point varies from solute to solute and solution to solution) More solute can be added in a solution, if its temperature is increased If temperature is decreased (cooling) the solute precipitates out Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar
Ch 6:Changes around us Reversible and irreversible Heat makes matter expand, cooling contracts Physical changes can be reversed using physical means only (exception alloys, evaporation, condensation, sublimation, desublimation or deposition) Chemical changes are usually not reversible using physical means alone (they need a chemical reaction to be reversed, ex: hardening of cement, POP rusting of iron etc.)
Ch 7: Getting to know plants ), sepals (shy, buds, I s Stamens (male: anther and filament) and pistil (female, innermost: stigma, style, ovary containing ovules) Tap roots = reticulate venation, Fibrous roots = parallel venation Herbarium: Collection of leaves in a book If the sepals of a flower are jointed, then the pistil is jointed to the petal. If the petals of a flower are jointed together, then the pistil is jointed to the the petal. Answer : It may or may not be true,
Ch 8: Body movements Run, fly, jump, creep, crawl, slither, swim, walk Joints: Articulation between bones, cartilage, tendons etc. Movement (except atskull, sacral, sternal, and pelvic bones) and stability Ball and socket joint- cavity (hollow space) + head/ball of a bone, huge range, shoulder and hip joint Pivotal joint- Neck (median atlanto-axial joint), Radio ulnar joints (both), IV only rotation allowed Hingejoint movement only on one axis-wrist and knee joint Fixed ioint. Cant move, skull joints, upper jaw with skull
Ch 8:Body movements dy Skeleton- framework of bones in our body, gives us shape, X-Ray. Rib cage: Sternum (chest bone) + Vertebral column are connected thorough 24 (12*2) ribs, 7 (true ribs, attach directly to sternum)+ 3 (false ribs, attach through coastal cartilages to 7th rib +2 (floating ribs, hanging ribs) - called thorax, thoracic cavity shoulder bones, pelvic are not as hard as the bones and which can be bent. These are called cartilage.
Ch 8:Body movements Muscles, contraction to bulging (Shorter, stiffer and thicker), works in pars (contraction + relaxation), only pull, at least 2 muscles are required to work for movement on a joint. Earthworm has muscles, no bones, tiny bristle hairs, eats soils and move forward and excrete, very helpful for farming * Snail have one shell, which is dragged by strong foot muscles Cockroaches have 3 pair of legs, can walk, climb and fly, thick exoskeleton with joints
Ch 8: Body movements Birds have pneumatic and hollow bones with strong muscles Fishes have small head and tail, with streamlined body, series of jerks in strong muscles, with tail assisting in the direction, fins help in the balance Snakes slithers, forming loops (give forward push by pressing against the ground, sideways and not in a straight-line), long backbone, small muscles, interconnecting backbone, ribs and skin