physical and chemical change the change does not actually make any new substance, we say it is a...
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PHYSICAL AND
CHEMICAL CHANGE
• The change does not actually make any new substance, we say it is a physical change.
• Most physical changes are quite easy to reverse. Some reactions are fast and some are slow.
PHYSICAL CHANGENo new
substance made
Easily reversed
Sharing of cake
Drilling of iron
Here are more examples :
Evaporation of water
Melting of ice
Dissolving of sugar in water
Powdering the sugar
Breaking of glass
Tearing of paper
Chemical ChangesChemical Changes
Changes that cause to produce a Changes that cause to produce a new substance are called as new substance are called as Chemical Chemical ChangesChanges which are which are relatedrelated with with innerinner propertiesproperties of substances, such as : of substances, such as :
Breaking the bonds between atoms in Breaking the bonds between atoms in molecules molecules
Forming new bonds between atomsForming new bonds between atoms
Generally we can say that chemical changes are notnot reversablereversable but someones are reversible.
For example :
C + O2 CO2
CHEMICAL CHANGENew substance(s)
made
Not easily reversed
Baking of cake
Rusting of iron
Here are more examples :
Burning of candle
Changing of CO to CO2
Freezing of cement
Spoiling of fruit
Rusting of iron
Cooking of egg
Chemical changes (reactions) are shown with symbols and formulas is called chemical equation. By this way chemical reactions can be shown easily.
For example:2Na(s) + 2H2O(l) →
2NaOH(aq) + ↑H2(g) + Q(heat)
Multiple Choice Question 1Multiple Choice Question 1
Which is true for physical change?
• No new substances are produced
• Frying of potato is a physical change
• Cooking of egg is a physical change
• New substances are produced
• They are not easily reversed
Multiple Choice Question 2Multiple Choice Question 2
Which is true for chemical change?
• No new substances are produced
• Drilling of iron is a chemical change
• Rusting of iron is a chemical change
• Dividing of an apple is a chemical change
• Easily reversed
Multiple Choice Question 3Multiple Choice Question 3
Which one of the following is chemical change?
• Dividing of apple
• Frying of aubergine
• Cutting of wood
• Peeling of apple