Question

V) Circle the odd one out 2.a. Burning of paper b. Rusting c. Milk into curd d. chemical changes d. Water into ice​

Answer 1

a. Burning of paper: chemical change; on burning the paper's chemical properties has changed to that of ashes - it has changed both chemically and physically .

b. Rusting: Rusting is oxidizing of iron to form metal oxide. On contact with atmospheric moisture (or liquid) and oxygen, it undergoes reaction to form a layer of rust on it's surface which is a chemical reaction.

c. Milk to curd: Curdling of milk occurs on the drop in the pH levels to clump up proteins and form curd which to inclined towards the more acidic side. There in a change in it's chemical state and hence it's a chemical change.

d. Water to ice: Freezing is the process of converting liquid to a solid on dropping temperatures to a 0°C or 32°F. Here, we can observe a change in water's physical state and not it's chemical change, solidified water is still water with a different name and temperature. There is no change in it chemical or molecular state, therefore, it's a physical state.

Answer: b. water to ice - physical change