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GSEB Solutions for Class 6 Science and Technology – Changes Aroun Us

GSEB Solutions for Class 6 Science and Technology – Changes Aroun Us (English Medium)

GSEB SolutionsMathsScience
Exercise 47:

Solution 1(a):
The changes which are brought about nature itself are called natural changes. These changes are beyond the control of man.
Example: Change of season, Tides in the sea, Ageing of plants, Landslides etc.

Solution 1(b):
The changes which are brought about by man are called man-made changes. These changes are under the control of man.
Example: Formation of curd, Burning of fuels, Cutting nails, Switching on an electric fan etc.

Exercise 48:

Solution 1(a):
Examples of reversible changes are as follows:

  1. Melting of ice
  2. Pulling of rubber band
  3. Folding of paper
  4. Evaporation of water

Solution 1(a):
Examples of non-reversible changes are as follows:

  1. Burning of a matchstick
  2. Germination of seed
  3. Rusting of iron
  4. Burning of fire crackers

Solution 1(c):
Changes in which physical properties like shape, size and state change without formation of a new substance are called Physical changes.
Examples: Melting of wax, Boiling of water, Expansion of iron on heating etc.

Exercise 49:

Solution 1(a):
The changes which take place in a long period of time are called slow changes.
Example:

  1. Baking a chapatti
  2. Burning of paper
  3. Burning of wood.

The changes which take place in a short period of time are called fast changes.
Example:

  1. Burning a matchstick
  2. Burning of magnesium ribbon
  3. Evaporation of petrol

Solution 1(a):
Changes brought about by a person or the nature, which are harmful, are known as non-agreeable changes.
Example:

  1. Souring of milk
  2. Rusting of iron
  3. Spoiling of food
  4. Flooding of rivers

Solution 1(c):
Changes which are desired to occur that is we want them to take place are known as desirable changes.
Example:

  1. Germination of seeds
  2. Raining
  3. Growth of a child
  4. Healing of a wound

Exercise 50:

Solution 1(a):
Periodic changes are as follows:
Day and night
Heartbeat
Phases of the moon

Solution 1(a):
Changes that do not repeat themselves at regular intervals of time are called non-periodic changes.
Examples:

  1. Cyclone
  2. Earthquake

Solution 1(c):

  1. Movement of spring: Reversible change
  2. Germination of a broad bean: Non-reversible change
  3. Growth of human being: Slow change

Exercise 52:

Solution 1(a):

  1.  Calcium oxide (Quick lime) reacts with water to form calcium hydroxide, also called slaked lime.
    CaO + H2O → Ca(OH)2
    A lot of heat is produced in the reaction. Due to this, sometimes water boils.
  2.  When common salt is added to water, it forms a salt solution.

Exercise 53:

Solution 1(a):

  1. Blowing of wind: Natural, Desirable, Non-periodic
  2. Ebb-tide: Natural, Periodic
  3. Formation of curd from milk: Non-reversible, Desirable
  4. Rainfall: Natural, Desirable
  5. Heating of wax: Physical, Reversible
  6. Pressing a rubber ball: Physical, Reversible
  7. Preparing organic manure: Man-made, Non-reversible
  8. Frying puris: Man-made, Non-reversible, Desirable
  9. Ripening of mangoes: Desirable, Non-reversible, Slow
  10. Contamination of food: Non-agreeable