Quiz on Physical and Chemical Changes

What type of change is photosynthesis?

• Chemical change

• Biological change

• Mechanical change

• Physical change

Answer explanation

Photosynthesis is a process where plants convert carbon dioxide and water into glucose and oxygen using sunlight. This involves breaking and forming chemical bonds, making it a chemical change.

What happens when sugar is dissolved in water?

• Thermal change

• Biological change

• Physical change

• Chemical change

Answer explanation

When sugar dissolves in water, it undergoes a physical change. The sugar molecules disperse in the water, but their chemical structure remains unchanged, distinguishing it from a chemical change.

Which of the following is a physical change?

• Burning of coal

• Digestion of food

• Melting of wax

• Photosynthesis

Answer explanation

Melting of wax is a physical change because it alters the state of the wax from solid to liquid without changing its chemical composition. In contrast, burning coal, digestion of food, and photosynthesis involve chemical changes.

What is the chemical name of baking soda?

• Sodium bicarbonate

• Sodium carbonate

• Calcium carbonate

• Potassium bicarbonate

Answer explanation

The chemical name of baking soda is sodium bicarbonate, which is a compound consisting of sodium, hydrogen, carbon, and oxygen. The other options listed are different compounds with distinct chemical properties.

What is formed when carbon dioxide is passed through lime water?

• Calcium oxide

• Calcium carbonate

• Calcium hydroxide

• Calcium chloride

Answer explanation

When carbon dioxide is passed through lime water (calcium hydroxide), it reacts to form calcium carbonate, which causes the solution to turn cloudy. This is a classic test for carbon dioxide.

Which process is considered a chemical change?

• Cutting wood

• Rusting of iron

• Dissolving salt

• Melting ice

Answer explanation

Rusting of iron is a chemical change because it involves a reaction with oxygen, forming iron oxide. In contrast, cutting wood, dissolving salt, and melting ice are physical changes that do not alter the chemical composition.

What type of change occurs when a candle burns?

• Only physical change

• Only chemical change

• Both physical and chemical changes

• No change

Answer explanation

When a candle burns, the wax melts (physical change) and the wax reacts with oxygen to produce heat, light, carbon dioxide, and water (chemical change). Thus, both physical and chemical changes occur.

How can rusting of iron be prevented?

• By painting

• By freezing

• By dissolving

• By heating

Answer explanation

Rusting of iron can be prevented by painting, as it creates a protective barrier that keeps moisture and oxygen away from the metal. Freezing, dissolving, and heating do not effectively prevent rusting.

What is the result of burning wood?

• No change

• Reversible change

• Chemical change

• Physical change

Answer explanation

Burning wood results in a chemical change because it transforms the wood into ash, smoke, and gases through combustion, altering its chemical structure and properties.

What happens when baking soda is mixed with lemon juice?

• Chemical change

• Physical change

• Both changes

• No reaction

Answer explanation

When baking soda (a base) is mixed with lemon juice (an acid), they react to produce carbon dioxide gas, water, and a salt. This reaction is a chemical change because new substances are formed.