Olympiad Test: Physical & Chemical Changes

Burning of candle wick is an example of chemical change as wick gets burnt and new substance is formed with new property.

On Combustion, fuel is the substance which produces heat and light.

When water freezes it undergoes a physical change and no new substance is formed.

Boiling of water is a physical change as water vapour can be changed into water again by cooling.

Since the law of conservation of mass is valid under all circumstances, hence, mass always remains the same, whether a substance undergoes physical change or chemical change.

Then in 1909, a Belgian chemist named Leo Baekeland created the first entirely synthetic plastic—and it would revolutionize the way many consumer goods were manufactured. Baekeland called his plastic “Bakelite.”

Rusting of iron is a chemical change as rust is a new substance having new properties unlike the iron.

D is the correct option.Crystallization is the process by which we can obtain crystals of copper sulphate. In this process, a few drops of dilute sulphuric acid is added to water. The water is then boiled & as it starts boiling, copper sulphate powder is added with stirring. The powder must be added on till the solution becomes saturated.

Chemical changes are characterised by formation of new substance having new properties

The product formed by dissolving a substance into another is called a solution. Solution is a mixture.

Rusting of iron is slow change as it takes few days on the other hand burning of petrol is a fast change as it takes less than a second.

Ripening of fruit is a slow change as it takes time. Ripening of fruit is also desirable as we want to do show.

During chemical changes, change in colour, heat or temperature may takes place but not always the size and shape.

Metal wires expand on heating and contract on cooling. The electric wires become tight during winter due to expansion and tight during winter due to contraction.

The process of converting gas into liquid is called condensation. Condensation is a physical change.

The chemical name of Baking soda is Sodium hydrogen carbonates, which is basic in nature.

Air is a mixture of gases like nitrogen, oxygen and carbon dioxide along with other gases and other particles.

Tearing of paper in small piece is an example of physical change as no new substance is formed and properties remain same.

Magnesium ribbon burns with brilliant white light to produce magnesium oxide.

Melting of an ice cube is physical change.

Burning of candle is both physical and chemical change.

When the candle burns, the wax slowly melts which freezes after some time (Physical change).

Rusting is an oxidation reaction. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust.

When the magnesium metal burns it reacts with oxygen found in the air to form Magnesium Oxide, which is a compound.

Oxygen and magnesium come together in a chemical reaction to form this compound. After it burns, it forms a white powder of the magnesium oxide.