Maharashtra Board Class 7 Science Changes – Physical and Chemical
Distinguishing Between Types of Changes:
Physical change and chemical change:
Physical Change: In a physical change, the substance’s composition remains the same, and no new substance is formed. It involves changes in the physical state or appearance. Example: Melting ice into water.
Chemical Change: In a chemical change, one substance is transformed into another with different properties, and a new substance is formed. Example: Burning wood to produce ash and smoke.
Periodic change and non-periodic change:
Periodic Change: Periodic changes are those that occur at regular intervals of time, and their recurrence is predictable. Example: Day and night.
Non-Periodic Change: Non-periodic changes are those that do not have a fixed time interval for recurrence, and their timing is not predictable. Example: Earthquakes.
Natural change and man-made change:
Natural Change: Natural changes occur without human intervention and are a part of the natural processes. Example: Ripening of a fruit.
Man-Made Change: Man-made changes are brought about by human actions and interventions. Example: Baking bread.
Classifying the Changes:
Conversion of milk into yogurt:
This is a chemical change because the original substance (milk) is transformed into a new substance (yogurt) with different properties.
Bursting of a cracker:
This is a fast/quick change and a non-periodic change because it happens suddenly, and the timing is not predictable.
Occurrence of an earthquake:
This is a non-periodic change because earthquakes do not occur at regular intervals, and their timing is not predictable.
