PHYSICAL AND CHEMICAL CHANGE The change does not actually make any new substance, we say it is a...

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