物質的狀態：練習題

In the scientific sense, what defines a substance as being pure?

Which of the following best explains why the pressure of a gas in a container of constant volume increases when its temperature is raised?

Calculate the energy required to melt \(1.5\text{ kg}\) of a substance that is already at its melting point.

(Specific latent heat of fusion = \(210,000\text{ J/kg}\))

In the particle model, which state of matter is characterized by particles that are in a fixed, regular arrangement and can only vibrate about fixed positions?

According to the kinetic theory of gases, which of the following is true about the particles in a gas when the temperature is increased?

A sample of a gas is held in a rigid container at a constant volume. According to the particle model, explain why increasing the temperature of the gas causes its pressure to increase.

Explain, in terms of the particle model and internal energy, why the temperature of a substance does not change while it is undergoing a change of state, such as melting, even though it is being heated.

A student is investigating the properties of a gas trapped in a cylinder with a movable piston. The volume of the gas is kept constant throughout the experiment.

a) Explain, in terms of the kinetic theory of matter, why the pressure exerted by the gas increases as its temperature is raised. (3 points)

b) The gas in the cylinder has a mass of \(0.012\text{ kg}\). The specific heat capacity of the gas is \(720\text{ J/kg °C}\). Calculate the thermal energy required to increase the temperature of the gas from \(20\text{ °C}\) to \(85\text{ °C}\). (2 points)

A solid block of an unknown substance with a mass of \(2.5\text{ kg}\) is heated at a constant rate. The block is initially at its melting point. It takes \(15\text{ minutes}\) of heating at a rate of \(400\text{ W}\) (Joules per second) to completely melt the block into a liquid without changing its temperature.

a) Calculate the total energy supplied to the substance to cause this change of state. (2 points)

b) Calculate the specific latent heat of fusion for this substance. (2 points)

c) In a different experiment, a student measures the mass of a liquid sample to be \(0.54\text{ kg}\) and finds it occupies a volume of \(6.0 \times 10^{-4}\text{ m}^3\). Calculate the density of the liquid. (2 points)

d) Explain why the density of the substance generally decreases when it changes from a solid to a liquid, referring to the arrangement of particles. (2 points)