Cut a piece of paper in four squares and each square into further square pieces. Lay the pieces so that the pieces acquire the shape of original paper. Is there a change in the property of the paper?
Classify the changes involved in the following processes as physical or chemical changes.
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f) Digestion of food
State whether the following statements are true or false. In case a statement is false, write the correct statement in your notebook.
(a) Cutting a log of wood into pieces is a chemical change. (True/False)
(b) Formation of manure from leaves is a physical change. (True/False)
(c) Iron pipes coated with zinc do not get rusted easily. (True/False)
(d) Iron and rust are the same substances. (True/False)
(e) Condensation of steam is not a chemical change. (True/False)
Fill in the blanks in the following statements.
(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of ..........
(b) The chemical name of baking soda is ........ .
(c) Two methods by which rusting of iron can be prevented are ...... and ......... .
(d) Changes in which only ...... properties of a substance change are called physical changes.
(e) Changes in which new substances are formed are called.
When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of familiar process in which both the chemical and physical changes take place.
The gas we use in the kitchen is called Liquefied Petroleum Gas (LPG). In the cylinder, it exists as liquid. When it comes out of the cylinder, it becomes a gas (change A). Then, it burns (change B).
The following statements pertain to these changes. Choose the correct one.
(a) Process A is a chemical change
(b) Process B is a chemical change
(c) Both processes A and B are chemical changes
(d) None of the above processes is a chemical change
Anaerobic bacteria digest animal waste and produce biogas (change A). The biogas is then burnt as fuel (change B). The following statements pertain to these changes. Choose the correct one.
(a) Process A is a chemical change
(b) Process B is a chemical change
(c) Both processes A and B are chemical changes
(d) None of the above processes is a chemical change
