A fixed mass of gas in a glass tube is trapped by a seal at one end of the tube and by a column of mercury. The mercury is free to move within the tube. The tube is rotated slowly from the vertical as shown in Fig. 3.1 to the horizontal as shown in Fig. 3.2. The volume of the gas increases and its temperature remains constant. [Figure 3.1] [Figure 3.2]

1. (a)(i)Describe why rotating the tube changes the pressure of the gas in the sealed end.[1]
2. (a)(ii)Explain, using ideas about particles, why the pressure of the gas decreases when its volume increases.[3]
3. (b)In Fig. 3.1 the length of the mercury column is 0.30m. The density of mercury is 14000kg/m³. Atmospheric pressure is 1.0 × 10⁵ Pa. Calculate the pressure of the gas in the tube. pressure = ................................................. Pa[3]
4. (c)The pressure of a different sample of gas changes at constant temperature. Fig. 3.3 shows one point, marked X, on a graph of pressure against volume for the gas sample. At X the pressure of the gas is P₀ and its volume is V₀. [Figure 3.3] On Fig. 3.3, sketch the graph as the pressure of the gas decreases from 2P₀ to ½P₀.[2]

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