हिंदी
Maharashtra State BoardSSC (English Medium) 7th Standard

Classification of Change: Chemical Changes

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Topics

  • Chemical and Physical Changes
  • Experiment

Introduction:

A chemical change happens when one substance is transformed into a completely new substance with different properties.

Raw Mango to Ripe Mango

  • The mango changes colour, taste, and composition as sugars and other compounds form.
  • Type: Chemical change because a new substance (sugar) is produced, and the change cannot be reversed.

Other examples include the burning of wood, cooking of food, rusting of iron, etc.

Experiment

1. Aim: To observe the change that occurs when sugar is heated and classify the type of change.

2. Requirements: evaporating dish, sugar, burner, tripod stand, and tongs (to handle hot equipment).

3. Procedure

  • Place some sugar in the evaporating dish. Set the dish on a tripod stand and light the burner beneath it.
  • Heat the sugar gently and observe the changes. As heating continues, the sugar will first melt and then change colour.
  • Stop heating when a blackish substance forms at the bottom of the dish.
  • Carefully remove the dish using tongs and allow it to cool.

4. Observations: The sugar first melts into a liquid. After more heating, it turns brown and finally forms a black residue (carbon).

5. Conclusion

Type of Change: This is a chemical change because new substances (carbon and gases) are formed, and the process is irreversible.

  • Melting sugar is a temporary, physical change (reversible).
  • Burning sugar to form black carbon is a permanent chemical change (irreversible).
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