A block of wood is floating in water at `0^@ C`. The temperature of water is slowly raised from `0^@ C` to `10^@ C`. How will the precentage of volume of block above water level change with rise in temperature?

Options

A. increase
B. decrease
C. first increase and then decrease
D. first decrease and then increase

Explanation

To solve the problem, we need to analyze how the percentage of the volume of a wooden block floating in water changes as the temperature of the water is raised from 0°C to 10°C. Here are the steps to arrive at the solution:

### Step 1: Understand the Concept of Buoyancy
A block floating in water displaces a volume of water equal to the weight of the block. The percentage of the block's volume that is submerged in water depends on the density of the water and the density of the block.

### Step 2: Analyze the Density of Water
Water has an anomalous behavior when heated from 0°C to 4°C. Specifically, as the temperature of water increases from 0°C to 4°C, its density increases. After reaching 4°C, the density of water begins to decrease as the temperature continues to rise.

### Step 3: Effect of Temperature on Water Density
- From 0°C to 4°C: The density of water increases. This means that for a given weight of the wooden block, it will displace less volume of water (because the water is denser). Therefore, the percentage of the block above the water level will increase.
- From 4°C to 10°C: The density of water decreases. As the water becomes less dense, the wooden block will displace more volume of water for the same weight, leading to a decrease in the percentage of the block above the water level.

### Step 4: Conclusion
- As the temperature of the water rises from 0°C to 4°C, the percentage of the volume of the block above the water level increases.
- As the temperature rises from 4°C to 10°C, the percentage of the volume of the block above the water level decreases.
- Therefore, the overall effect is that the percentage of the volume of the block above the water level first increases and then decreases.

### Final Answer
The percentage of the volume of the block above the water level will first increase as the temperature rises from 0°C to 4°C and then decrease as the temperature rises from 4°C to 10°C.