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What is Isobars?

  Atoms of chemical elements having same atomic mass but a different atomic number are called Isobars. The sum of the number of protons and neutrons together form the atomic mass. Therefore, we can also say the number of nucleons present in the nucleus is equal to the atomic mass of an atom. It will have the same number of nucleons. The number of protons and neutrons alone will vary but the number of nucleons or the sum of protons and neutrons in isobars will always be same. Isobars always have different atomic structure because of the difference in atomic numbers. The number of neutrons makes up the difference in the number of nucleons. Therefore, they are always different chemical elements having same atomic masses. Thus, isobar has different chemical properties. For example : Iron and nickel have atomic number 26 and 28 respectively. However, the mass number is 58. Argon and calcium with atomic number 18 and 20, respectively. However, they have the same atomic mass 40.

What is Tyndall effect? Explain with an example.

 'Tyndall effect, also called Tyndall phenomenon, scattering of a beam of light by a medium containing small suspended particles.'

Ex - Smoke or Dust in a room, which makes visible a light beam entering a window. 

  • Short-wavelength blue light is scattered more strongly than long-wavelength red light.
  • The Tyndall effect occurs from particles roughly the same size as the wavelength of light. The effect is named for the 19th-century British physicist John Tyndall, who first studied it extensively.

                                           or

'The scattering of light by particles in its path is called Tyndall effect.'

When a beam of light enters a smoke-filled dark room through a small hole, then its path becomes visible to us. The tiny dust particles present in the air of room scatter the beam of light all around the room. Thus, scattering of light makes the particles visible. Tyndall effect can also be observed when sunlight passes through a canopy of a dense forest. Here, tiny water droplets in the mist scatter light.

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How would you distinguish between baking powder and washing soda by heating?

Answer :  Baking soda (NaHCO 3 ) liberates carbon dioxide gas on heating, confirmed by passing it in lime water. Whereas on heating washing soda Na 2 CO 3 .10H 2 O water of crystallisation is given out, the salt becomes anhydrous. Reaction: 2NaHCO 3  → Na 2 CO 3  + H 2 O + CO 2 Na 2 CO 3 .10H 2 O → Na 2 CO 3  + 10 H 2 O

Give some examples of rancidity and some precautions also.

example of rancidity Some examples of rancidity are - Food when exposed to atmospheric air for a long duration becomes rancid. Butter changes its taste and smell when kept in an open atmosphere for a longer duration. Some precaution to prevent rancidity : Food should be kept in sealed containers. Food that needs to be refrigerated. Foods containing fat and oil can be packaged in nitrogen gas to prevent rancidity. To avoid rancidity, food should be stored away from light. Antioxidants can be added to food.

What is rancidity?

The oxidation of oils or fats in food resulting in a bad taste and smell is called rancidity.  OR It is a condition in which aerial oxidation of unsaturated fat present in food gives it an unpleasant flavour and odour. Rancidity makes food undesirable for consumption. This process is also called rancidification.