A sealed rigid container holds gas that is warmed up. Figure 5 offers four graphs, A to D, of pressure against temperature in degrees Celsius.
Pick the graph in Figure 5 that shows how the gas pressure changes with temperature.
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When the gas is warmed, its particles move faster and hit the container walls harder and more often, so pressure rises steadily, giving a straight line sloping upwards. The gas still has pressure at 0 degrees Celsius, so the line cuts the pressure axis above zero. That is graph A. Graph D also rises, but it starts at the origin, which would mean zero pressure at 0 degrees Celsius. A line through the origin only happens if temperature is measured from absolute zero, on the kelvin scale. Graph B shows pressure falling as the gas heats, and graph C has pressure highest at 0 degrees Celsius and falling either side, so neither matches the particle model.
How the marks are earned
- Choose graph A: pressure rises steadily as temperature rises, giving a rising straight line that does not pass through the origin because the axis is in degrees Celsius.
- One answer only: two answers earn nothing, and a circled or underlined right option counts if the box is blank.