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Change in internal energy when a liquid boils or is heated (dU = Q - P dV)

This type of question, asked 3 times: 24 Jan 2023, 11 Apr 2023, 24 Jan 2026 S1. All 3 questions below, oldest first.

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  1. Question 1

    24 Jan 2023

    12
    1 g1\text{ }g of a liquid is converted to vapour at 3×105 Pa3 \times10^{5}\text{ }Pa pressure. If 10%10\% of the heat supplied is used for increasing the volume by 1600 cm31600{\text{ }cm}^{3} during this phase change, then the increase in internal energy in the process will be:

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  2. Question 2

    11 Apr 2023

    10
    1 kg1\text{ }kg of water at 100∘C100^{\circ}C is converted into steam at 100∘C100^{\circ}C by boiling at atmospheric pressure. The volume of water changes from 1.00×10−3 m31.00 \times10^{- 3}{\text{ }m}^{3} as a liquid to 1.671 m31.671{\text{ }m}^{3} as steam. The change in internal energy of the system during the process will be (Given latent heat of vaporisation =2257 kJ/kg= 2257\text{ }kJ/kg. Atmospheric pressure =1×105 Pa= 1 \times10^{5}\text{ }Pa )

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  3. Question 3

    24 Jan 2026 S1

    4
    Density of water at 4∘C4^{\circ}C and 20∘C20^{\circ}C are 1000 kg/m31000\text{ }kg/m^{3} and 998 kg/m3998\text{ }kg/m^{3} respectively. The increase in internal energy of 4 kg water when it is heated from 4 ∘C4\ ^{\circ}C to 20∘C20^{\circ}C is ____\_\_\_\_ J. (Specific heat capacity of water =4200 J/kg.K= 4200\text{ }J/kg.K and 1 atmospheric pressure =105 Pa= 10^{5}\text{ }Pa)

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