Question

A substance has a boiling point of 78 °C. Which of the following is true about the substance?

When the substance is heated, its temperature will start rising above 78 °C after 50% of the liquid has changed to vapors.
When the substance is heated, its temperature will start rising above 78 °C after 100% of the solid has changed to liquid.
When the substance is cooled, its temperature will fall below 78 °C after 100% of the vapor has changed to liquid.
When the substance is cooled, its temperature will fall below 78 °C after 50% of the liquid has changed to solid.

Answer 1

When the substance is cooled, its temperature will fall below 78 °C after 100% of the vapor has changed to liquid.

Step-by-step explanation:

• Boiling point is the temperature at which a liquid changes state from liquid form to gaseous form without change in temperature. It may defined as the temperature at which the vapor pressure is equal to the pressure of the gas above the liquid.
• A liquid with a boiling point of 78°C, it means that, when the liquid is heated, its temperature will start rising above 78 °C after 100% of the liquid has changed to vapors. Additionally, when the liquid is cooled, its temperature will fall below 78 °C after 100% of the vapor has changed to liquid.