Points from 9th Std SSC Science book – Useful for Homibhabha Exam

A few points from 9th Std SSC Board Science Textbooks


  1. Sulphamic acid (H3NSO3) is a solid inorganic acid.
  2. Sodium bicarbonate is formed on passing CO2 through an aqueous solution of sodium carbonate. (sodium bicarbonate = baking soda) Chemical equation of the reaction
    Na2CO3 + H2O + CO2 — > 2NaHCO3
  3. Liquid CO2 is used as solvent in modern eco-friendly dry cleaning.
  4. Methane and chlorine gases react with each other at the temperature of 250 deg C to 400 deg C in presence of ultraviolet light and form mainly methyl chloride (chloromethane) and hydrogen chloride. This reaction is called chlorination of methane.
    Chemical reaction
    CH4 +Cl2 (Light) — > CH3Cl + HCl
  5. Electrolysis of salt water: 2NaCl + 2H2O — > 2NaOH + Cl2 + H2
  6. The 25% aqueous solution of salt is called saturated brine. When 1/5 of this solution is evaporated the dissolved salt gets crystallized and salt gets separated from the solution.
  7. Chlorine is inconvenient to handle because of its gaseous state. Instead, the solid bleaching powder which has the same effect is more convenient to use. Bleaching powder undergoes slow decomposition due to the carbon dioxide in air and chlorine gas is released. Bleaching powder gets its property because of this release of chlorine gas.
    Bleaching powder (Calcium Oxychloride CaOCl2)
    CaOCl2 + CO2 — > CaCO3 + Cl2
  8. Bleaching powder is obtained by the reaction of chlorine gas with slaked lime.
    Ca(OH)2 + Cl2 — > CaOCl2 + H2O
  9. Dilute sulphuric acid and dilute hydrochloric acid react rapidly with bleaching powder to release chlorine gas completely.
    CaOCl2 + H2SO4 — >CaSO4 + Cl2 + H2O
  10. Washing soda reacts with hard water to form insoluble carbonates:
    MgCl2 (aq)+ Na2CO3 (s) — > MgCO3(s) + 2 NaCl (s)
  11. Crystaline soda. Loses water to form powder soda
    Na2CO3 .10 H2O (crystalline soda) — > Na2CO3 .
    H2O white powder (washing soda)
  12. Washing soda hygroscopic, that is, it absorbs moisture if left exposed to air.
  13. Borax (Na2B4O7.10H2O)
  14. Sodium sulphate (Glauber’s salt Na2SO4.10 H2O)
  15. When oil or animal fat is boiled with an aqueous solution of sodium or potassium hydroxide, sodium or potassium salts of carboxylic acids (fatty acids) are formed. These salts are called soap. When soap is mixed with hard water calcium and magnesium salts of fatty acids are formed. These being water insoluble they form a precipitate and that is why lather is not formed.
  16. Tetrazene, sunset yellow are artificial food colours used extensively
  17. Lipstick contains a dye named carmine. It does not affect lips but causes stomach disorders.
  18. Deodorants contain parabens (methyl, ethyl, propyl, benzyl and butyl) and also alcohol in large proportions. Aluminium – Zirconium compounds are the most harmful chemicals in the deodorant.
  19. In 1608, spectacle maker and researcher, Hans Lippershey discovered that seeing through two lenses kept one behind the other, seems to brings objects closer to us. He thus made the first telescope. Galileo made a telescope in 1609
  20. The images formed by lenses have errors of colours. This is called chromatic aberration.
  21. Biggest optical telescope in India, having a mirror of 3.6 m diameter is situated in the Aryabhatt Research Institute of Experimental Sciences, Nainital.
  22. Giant Meterwave Radio Telescope (GMRT) has been erected at Narayangaon near Pune.


  1. JL Proust showed law of constant proportion. Elements are in proportion in a compound
  2. Rhizobium is useful for nitrogen fixation on roots of legumes. Seeds of cereals and other plants (other than legumes) are soaked in rhizobia (solution or powder) before sowing, this is rhizobial inoculation.
  3. Alcanivorax bacteria cleans oil spill in ocean.
  4. Yeast Saccharomyces is used to make Alcohol ethanol C2H5OH and biodiesel.
  5. Yeast Saccharomyces cereviceae absorbs pollutant arsenic.
  6. Yeast Yarrowia lipolytica absorbs heavy metals in industry and toxins produces while making palm oil.
  7. Broad spectrum antibiotics : are useful against many bacteria. e.g. ampicillin, amoxicillin, tetracyclin.
  8. Narrow spectrum antibiotics : against a particular bacteria. e.g. penicillin, gentamycin, erythromycin. Penicillin controls infections of staphylocoocus , clostridia, streptococci bacteria,diseases like pneumonia, scarlet fever.
  9. Alexander Fleming observed (3rd sept 1928) staphylocoocus bacteria were destroyed by fungus Penicillium.
  10. Fungi causes dandruff in hair, ringworm, scabies as skin diseases. fungi produce harmful chemicals called mycotoxins and spoils food.
  11. Ants grow fungus in ant hill (termitarium) to use as food. Wasps and other insects lay eggs in fugus colony.
  12. National Institute of Virology is in Pune.
  13. Harmful microbes: Clostridium botulinum (Van Ermengem proved food poisoning. Spoilt cooked food causes food poisoning. rod shaped bacteria produce bottle shaped endospores. they are anaerobic.
  14. Ida Bengston herself infected due to Typhus while doing research. She was honoured ‘typhus medal’. Her research was on antibiotics for gas gangrene.
  15. Indian Institute of Ecology and Environment, Delhi
  16. Lindeman in 1942 studied food chain and energy flow through it. Charles Elton proposed ecological pyramid In 1927. It is also called Eltonian pyramid. He studied Tundra Ecosystem of Beer islands in England.
  17. Biogas contains about 55% to 60% methane and the rest is carbon dioxide. Production of biogas is an anaerobic process. It takes place in two stages.
  18. Production of acids. The microbes act on the biodegradable complex organic compound and produce organic acids.
  19. Methane gas production The methanogenic bacteria act on the organic acids to produce methane gas CH3COOH — > CH4 + CO2
  20. Proper co-ordination between various systems of an organism helps to maintain a state of equilibrium called ‘homeostasis’ which is necessary for the optimal efficiency of the body.
  21. Some cells in the body of living organisms are ‘totipotent’, that is if provided a proper environment, a new organism can grow from these cells.
  22. Layers for egg production: Leghorn, Minorca, Ancona, Lehman
  23. Broilers for meat: Brahma, Long, Cochin, Aseel
  24. Bombyx mori is variety of silk worm
  25. GM crops. For example,
    Maize : MON 810, MON 863.
    Potato : Amflora
    Rice : Golden Rice
    Soybean : Vistive Gold
    Tomato : Vaishali
    Cotton : BT cotton