When water is heated from 0°C to 20°C, how does its value change?

The correct answer is Option 4 because water exhibits a unique physical property known as anomalous expansion between 0°C and 4°C.

Typically, liquids expand when heated. However, when water is heated from 0°C, its density increases and its volume decreases until it reaches 4°C, where it attains its maximum density. Beyond 4°C, water behaves normally; as the temperature continues to rise toward 20°C, the molecular motion increases, causing the volume to increase.

• 0°C to 4°C: Volume decreases (Density increases).
• 4°C to 20°C: Volume increases (Density decreases).

Therefore, the volume first decreases and then increases. Option 1 is incorrect as it ignores the contraction phase; Option 2 is incorrect as it ignores expansion after 4°C; and Option 3 is the exact opposite of water's actual behavior.