Dhruv got a slab of chocolate from his friend on his birthday. He kept it in his bag. On reaching home, he opened his bag and found a brown sticky liquid oozing out of the wrapper. It had spread over some of his books. What do you think has happened?

Explanation

### Step-by-Step Solution:

1. **Understanding the Initial Condition**: Dhruv received a slab of chocolate, which is typically solid at room temperature. Chocolate contains cocoa solids, sugar, and fat, and when it is cold, it remains in a solid state.

2. **Temperature Change**: After Dhruv kept the chocolate in his bag, the temperature inside the bag likely increased. The bag was not refrigerated and was at a temperature around 30 degrees Celsius, which is higher than the solidification point of chocolate.

3. **Phase Transition**: As the temperature increased, the chocolate began to absorb heat. The heat caused the cocoa solids and fats in the chocolate to melt. This process is known as melting, where a solid turns into a liquid when heat is applied.

...