Write short notes on fast and irreversible change
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Class-VI
Science
Amogh Sahhai
Jan 11, 2015
What is the differance between a)fast and slow change b)reversible and irreversible change c)chemical and physical d)desirable and non-..
What is the differance between a)fast and slow change b)reversible and irreversible change c)chemical and physicald)desirable and non-desirable changee)natural and man-made changef)periodic and non - periodic change
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Swathi Ambati
Member since Apr 28, 2014
a) Fast changes occur with in seconds or minutes. Whereas slow changes take place very slowly and may take hours, days or months to complete. Examples for fast changes: Burning of paper, Burning of a candle. Examples for slow changes: Rusting of iron, Germination of seed, curdling of milk etc. b) A reversible change is a change that can be undone or reversed.Examples: Melting ice, Boiling, evaporation and condensation .An irreversible change is a permanent change that cannot be undone. In an irreversible change, new substances are formed.Examples: Cake batter is made from eggs, flour, sugar and butter. c) A change in the physical properties such as shape, size, color and state of a substance is a physical change.Examples of physical changes are melting of ice, boiling of water, freezing of water, Condensation, Crystallization and heating of metals to red hot, etc. A chemical change occurs when one or more substances are converted into one or more new substances. Examples: Formation of rust on the iron bench or articles of iron kept in the open for a long time, Digestion of food, burning of magnesium ribbon, the reaction between vinegar and baking soda, etc. d) Changes that are useful to us are known as desirable changes. Example: Cooking of food Changes that are not useful to us are known as undesirable changes. Example; Spoilage of food. e) Changes that are occur in nature are called natural changes.Example; Change in seasons. Changes that are made by human beings are called man made changes. Example: Construction of dams, buildings etc. f ) Changes which are repeated after regular intervals of time are called as periodic changes. Example: Occurrence of day and night. Changes which are not repeated after regular intervals of time are called as periodic changes. Example: Floods, cyclones, etc