Question

$1\text{L}$ of water is taken into a vessel and is heated to ${80}^{\circ }\text{C}$. The contents of the vessel are transferred into a thermos flask of $1\text{L}$ capacity. It is observed that there is more water left in the vessel. Explain the reason for this.

Answer 1

The reason is the thermal expansion of water. Solids, liquids, and gases expand on heating and contract on cooling. When $1\text{L}$ of water was heated, its volume increases beyond $1\text{L}$. That is why, when the contents are transferred into a thermos flask, there is some hot water left in the vessel.