A perfectly insulated flask contains a sample of metal M at a temperature of -10 °C - AQA - A-Level Physics - Question 1 - 2020 - Paper 2

The energy transferred reduces the number of nearest atomic neighbors, allowing the atoms to move their centers of vibration. As the energy continues to increase, it may also break some of the atomic bonds, changing the arrangement from a crystalline to an amorphous state.

During the time interval tA to tB, the total or mean kinetic energy remains constant while the total or mean potential energy increases. The energy supplied is used to overcome the intermolecular forces, leading to a change of state.

During the time interval tB to tC, the atoms gain kinetic energy as they are heated further. The mean speed of the atoms increases, leading to more vigorous motion as they transition from liquid to gas.

Using the formula for specific heat capacity, we can determine:

$Q = mc riangle T$ Where:

• Q is the energy supplied (in joules),
• m is the mass (0.25 kg),
• c is the specific heat capacity (unknown),
• $riangle T$ is the change in temperature.

Given that the temperature changes from -10 °C to 28 °C, we find:

$riangle T = 28 - (-10) = 38 °C$

Now, substituting into the formula:

$Q = 35 W imes ( ext{time in seconds})$ Assuming the time taken for this heating process is 60 seconds:

$Q = 35 W imes 60 s = 2100 J$

Thus, plugging values into the specific heat formula:

$2100 = 0.25 imes c imes 38$ Solving for c:

c = rac{2100}{0.25 imes 38} = 2100 / 9.5 = 221.05 J kg^{-1} K^{-1}

Therefore, the specific heat capacity of M is approximately 221.05 J kg⁻¹ K⁻¹.

Based on the given latent heats of fusion and the calculated specific heat capacity, metal M is identified as Gallium.