Question
Fri April 11, 2014 By: Rithikjaiswal Rithik

Give 10 properties of chemical &physical changes?

Expert Reply
Sat April 12, 2014
  • Physical Change: A change which alters some physical properties (e.g. colour, state, texture, magnetic or electrical conditions, density) etc. and does not involve a change in the molecular structure, i.e. no new substance is formed.
  • Chemical Change: A change which alters the specific properties of a material by bringing about a change in which the original substance gives rise to one or more new substances with different composition and properties.

 

Physical change

Chemical change

Characteristics

  1. No new substance is formed.
  2. Composition of the original substance remains unchanged.
  3. The change is temporary and reversible.
  4. There is no change in the weight of the substance.
  5. There is no gain or loss of energy.

Energy required for completion of a physical change is released when the change is reversed. Example: Ice changes to water.

 

  1. New products are formed.
  2. Composition of the reactants changes, resulting in the formation of one or more new substances.
  3. The change is permanent and irreversible.
  4. The weight of a substance undergoing a chemical change usually changes.
  5. It is always accompanied by the absorption or liberation of energy.

Energy in the form of heat, light, pressure etc. is required for a chemical change.

Examples

The change of state of matter

  1. Melting: Solids to liquids
  2. Freezing: Liquids to solids
  3. Vaporisation: Liquids to gases
  4. Liquefaction: Gases to liquids

 

  • Expansion or contraction of substances when heated or cooled. Melting of substances, such as the melting of wax.
  • Examples: Boiling of milk, melting of butter, magnetisation of iron, ringing of an electric bell, water cycle, evaporation, drying of wet clothes, breaking of glass.

Chemical reactions taking place

  1. Addition of acids to substances
  2. Fermentation of substances
  3. Respiration
  4. Dehydration of carbohydrates

 

  • Burning of substances in air and oxygen, such as the burning of magnesium in air.
  • Examples: Ripening of fruits, rusting of iron, changes in electrochemical cell, curdling of milk, carbon cycle, burning of wood, clotting of blood, decaying of organic matter, butter turning rancid.
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