Question

below its melting point. over the course of about 15 minutes, the container is heated. at first, the application of heat causes the temperature of the substance to increase until it reaches its melting point temperature. at its melting point temperature, heat is continually added, causing the solid to transition to a liquid at a constant temperature. once all the solid has melted, the substance is heated to its boiling point temperature. at its boiling point temperature, the addition of heat causes the liquid to transition to a gas at a constant temperature. once all the liquid has boiled, the sample continues to be heated (cautiously), causing the temperature of the gas to increase. this process is depicted in figure 1.
figure 1
chart with time (sec) on x - axis and temperature (°c) on y - axis, with points a, b, c, d, e
according to figure 1, at what temperature does the substance transition between the liquid state and the gas state?
○ approximately - 65°c
○ approximately - 7°c
○ approximately 135°c
○ approximately 190°c

Explanation:

Step1: Identify phase transition region

The transition between liquid and gas is boiling, which occurs at a constant temperature (flat line on the graph). Locate the flat segment representing boiling (liquid to gas).

Step2: Determine temperature of boiling

The flat segment (points D and around) has a temperature. From the graph, the y - axis (temperature) at the boiling flat line is approximately \(190^{\circ}\text{C}\). Check the options: the option with approximately \(190^{\circ}\text{C}\) is the correct one.

Answer:

Approximately \(190^{\circ}\text{C}\) (the option with this temperature, e.g., if the options are as given, the last option: Approximately \(190^{\circ}\text{C}\))