Final answer:
At 31 degrees Celsius, water is above its melting point and below its boiling point, which places it in the liquid state. This temperature is well within the normal range for water to be a liquid under standard atmospheric conditions. Therefore, the correct option is b) Liquid.
Step-by-step explanation:
When considering the state of matter for water at a given temperature, we must consider the typical properties and behavior of water under normal atmospheric conditions. At a temperature of 31 degrees Celsius, water is above its melting point of 0°C and below its boiling point of 100°C. This places it well within the range for the liquid state.
Under standard atmospheric pressure, water exists in three main states:
• Solid below 0°C when it is commonly known as ice.
• Liquid between 0°C and 100°C, which is the state most familiar to us as 'water'.
• Gas above 100°C when it becomes steam or vapor.
The kinetic molecular theory helps us understand these states. A solid is characterized by molecules tightly packed together in a fixed structure. A liquid, like the water at 31°C, has molecules that are less tightly packed than a solid, allowing it to flow and take the shape of its container. A gas, on the other hand, has molecules that are far apart and moving freely. Considering our knowledge of the properties of water and its behavior with temperature changes, the correct option for the state of matter of water at 31 degrees Celsius is b) Liquid.