物理物態變化 DSE、CE 選擇題（第 5 頁）

41.

Five different solids, each of mass $1$ kg, are heated by identical immersion heaters for $10$ minutes. The following graphs show their heating curves. Assuming no loss in heat, which solid has the greatest specific latent heat of fusion ?

Four temperature-time heating curves A to D over 0 to 10 min, each with a horizontal melting section of different length

42.

Arrange the following in ascending order. $E_1=$ Energy required to melt $1$ kg of ice at $0^\circ\mathrm{C}$ $E_2=$ Energy required to raise the temperature of $1$ kg of copper by $1^\circ\mathrm{C}$ $E_3=$ Energy required to vaporize $1$ kg of water at $100^\circ\mathrm{C}$ $E_4=$ Energy required to raise the temperature of $1$ kg of water by $1^\circ\mathrm{C}$

43.

Cooling curve of liquid naphthalene with regions P, Q, R and S along the time axis

The graph shows the cooling curve of liquid naphthalene. In which region has naphthalene completely solidified ?

44.

Heat is needed to keep water boiling because energy is required to

(1)increase the potential energy of the water molecules.

(2)increase the kinetic energy of the water molecules.

(3)increase the average speed of the water molecules.

45.

If an immersion heater takes $10$ minutes to bring a cup of water to its boiling point $100^\circ\mathrm{C}$ from the room temperature of $20^\circ\mathrm{C}$ , what will be the time taken for the boiling water to vaporize completely ? (Specific heat capacity of water $= 4.2\ \mathrm{kJ\,kg^{-1}\,{}^\circ C^{-1}}$ ; specific latent heat of steam $= 2268\ \mathrm{kJ\,kg^{-1}}$ .)

46.

Cooling curve of liquid naphthalene: temperature falls from A (80 degrees C) to B, stays at about 70 degrees C between B and C, then falls to D

A cooling curve for liquid naphthalene is shown above. From the graph, which of the following statement(s) is/are true ?

(1)The melting point of naphthalene is around

70^\circ\mathrm{C}

.

(2)In the period

BC

, only liquid naphthalene is present.

(3)In the period

BC

, no energy is given by naphthalene to the surroundings.

47.

It is given that : the specific latent heat of fusion of ice $= 3.3\times10^5\ \mathrm{J\,kg^{-1}}$ the specific latent heat of vaporization of water $= 2.3\times10^6\ \mathrm{J\,kg^{-1}}$ If $1$ kg of ice at $0^\circ\mathrm{C}$ and $1$ kg of steam at $100^\circ\mathrm{C}$ are mixed in a well insulated vessel, the result will be

48.

Temperature-time graph: rises from 20 degrees C to 70 degrees C in 100 s, stays at 70 degrees C until 200 s, then rises again

A solid substance of mass $2$ kg and specific heat capacity $1000\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$ is heated uniformly by a constant heat source. The temperature-time graph of the substance is shown in the graph. Assuming that no heat is lost, find from the graph the specific latent heat of fusion of the substance.

49.

The following data shows the thermal properties of four substances $P$ , $Q$ , $R$ and $S$ :

Substance	$P$	$Q$	$R$	$S$
Melting point	$40$ K	$98$ K	$114$ K	$270$ K
Boiling point	$280$ K	$880$ K	$180$ K	$370$ K
Average specific heat capacity in $\mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$	$800$	$1200$	$226$	$40$
Specific latent heat of fusion in $\mathrm{J\,kg^{-1}}$	$2\times10^4$	$11\times10^4$	$5\times10^4$	$33\times10^4$
Specific latent heat of vaporization in $\mathrm{J\,kg^{-1}}$	$30\times10^4$	$34\times10^4$	$40\times10^4$	$230\times10^4$

When the temperature of each substance is increased from $250$ K to $400$ K, which one will absorb the greatest amount of energy ?

50.

A liquid placed inside an insulated vessel is kept boiling by a heating coil immersed in it. When the power supplied to the coil is $42$ W, the liquid boils away at a rate of $10^{-4}$ kg s $^{-1}$ . What is the specific latent heat of vaporization of the liquid ?