Question

Which of the graphs below illustrates water boiling in Denver, Colorado? (Altitude 1,600 meters.)

Answer 1

Answer:

• The graphs that come with this question are in the picture attached.

• The answer is graph identified with the letter A.

Explanation:

The normal boiling point of water is 100°C. That is the temperature at which water boils when the atmospheric pressure is 1 atm, i.e. at sea level.

The liquids boil when its vapor pressure equals the atmospheric pressure; so the higher the atmospheric pressure the higher the boiling point, and the lower the atmospheric pressure the lower the boiling point.

Since, it is stated that the altitude of Denver, Colorado is 1,600 m, the atmosperic pressure (ther pressure exerted by the columnn of air above the place) is lower than 1 atm (atmospheric pressure at sea level).

Hence, water boiling point in Denver is lower than 100°C.

The graphs shown represent the temperature (T °C) as water is heated. Since when liquids boil their temperature remains constant during all the phase change, the flat portion of the graph represents the time during which the substance is boiling.

In the graph A, the flat portion is below 100°C; in the graph B, the flat portion is at 100 °C; in the graph C the flat part is above 100ªC, and, in graph D, there is not flat part. Then, the only graph that can illustrate water boiling in Denver, Colorado is the graph A.