Class 8 – Science Notes

Crops Types of Crops Preparation of Soil Sowing Manures Fertilisers Crop Rotation Irrigation Methods of Irrigation Weeding Harvesting Storage of Food Grains

Micro-Organisms Groups of Micro Organism Where do Micro Organism Live Useful Micro organism Making of Curd and Bread Commercial Use of Micro organism Medicinal Use of Micro organism Increasing Soil Fertility Cleaning the Environment Harmful Micro Organism Carriers of Disease causing micro organism Disease Causing Micro-Organism in Plants Food poisoning Preservation of Food Preservation by sun-drying, Heating, Cooling Preservation by Deep Freezing,Common Salt, Sugar Preservation of food by mustard oil and Vinegar, Chemicals, Pasteurisation, Air-tight Packets Nitrogen Fixation Nitrogen Cycle

Natural Resources Coal Products of Coal Petroleum Refining of Petroleum Natural Gas Petrochemicals

Combustion Conditions necessary for Combustion Lightning of matchstick Types of combustion Fire control Fuels Flame Structure of flame Burning of fuels leads to harmful products

Biodiversity and ecosystem Causes of deforestation Conservation of forests and wildlife Consequences of deforestation Biosphere reserve Flora and fauna Wildlife Sanctuary National Park Extinct and Endangered Species Red data book Recycling and Reforestation

Reproduction in animals Methods of Reproduction Gametes Fertilisation Sexual Reproduction in humans Development of embryo In Vitro Fertilisation Viviparous animals and Oviparous animals Fertilisation in hen Asexual Reproduction in animals Metamorphosis Cloning

Adolescence Puberty Changes At Puberty:Height, Voice, Body shape Changes at puberty:Pimple and acne, development of sex organs Secondary sexual characteristics in humans Hormones Reproductive Phase Adolescent Pregnancy How is sex of a baby determined Hormones Reproductive health

Force Force is due to interaction Force has magnitude as well as direction Effects of Force Contact force Non-contact forces Pressure Pressure exerted by liquids Pressure exerted by gases Atmospheric pressure Applications of atmospheric pressure

Static, sliding and rolling friction Factors affecting friction Cause of friction Friction Advantages of friction Disadvantages of friction Methods of increasing friction Methods of reducing friction Fluid friction

Noise pollution Musical instruments Noise and music Audible and Inaudible sound Characteristics of sound Amplitude, time-period and frequency of vibration Ears Speed of sound Sound needs a Medium for Propagation Sound produced by humans Sound is produced by vibrating object

Liquids conduct electricity Test for conduction of liquid Detection of weak current flowing through liquid Distilled, tap, sea and rain water Chemical effect of electric current Electroplating Weak conductors of electricity Purification of metal Uses of electroplating

Electric Charges Lightning Earthquake

Reflection of Light Formation of Image, Periscope, Kaleidoscope Human Eye