Question

Какое количество теплоты было передано куску свинца массой 100 г, если он находился исходно при температуре 27 °С, был нагрет до плавления и расплавился наполовину?Хозяйка поставила на газовую плиту кипятить 2 кг воды в алюминиевой кастрюле массой 0,5 кг. Какое количество теплоты должно выделиться при сгора­нии газа для того чтобы довести воду до кипения, если ее начальная температура 20 °С? При сгорании газа только 30% выделяющейся энергии идет на на­гревание кастрюли с водой.

Answer 1

Дано:
m=0.1
c=140(удельная теплоемкость)
С=25000(удельная теплота плавления)
t1=27
t2=327Q-?
__________
Решение
Q1=cm(t2-t1)= 4200
Q2=Cm/2=1250
Q=1250+4200=5450

Answer 2

Calculating Heat Transfer for Lead

To calculate the amount of heat transferred to the lead, we can use the formula:

Q = mcΔT

Where: - Q = heat transferred - m = mass of the substance - c = specific heat capacity - ΔT = change in temperature

Given: - Mass of lead, m = 100 g - Initial temperature, T1 = 27 °C - Final temperature (after melting), T2 = 327 °C (lead's melting point is 327 °C) - Lead is melted halfway, so the temperature change is ΔT = (T2 - T1) / 2

Using the specific heat capacity of lead, which is 0.128 J/g°C we can calculate the heat transferred.

Calculation:

Q = (100 g) * (0.128 J/g°C) * ((327 °C - 27 °C) / 2)

Result:

The amount of heat transferred to the lead is approximately 1920 J.

Heat Required to Boil Water

To find the heat required to boil the water, we can use the formula:

Q = mcΔT

Where: - Q = heat transferred - m = mass of the substance - c = specific heat capacity - ΔT = change in temperature

Given: - Mass of water, m = 2 kg - Initial temperature, T1 = 20 °C - Final temperature (boiling point), T2 = 100 °C - Specific heat capacity of water, c = 4.18 J/g°C - Heat required to boil water = Q_water + Q_container

The heat required to boil water is the sum of the heat required for the water and the heat required for the container.

Calculation:

Q_water = (2000 g) * (4.18 J/g°C) * (100 °C - 20 °C)

Result:

The heat required to boil the water is approximately 664,000 J.

Additional Information

Given that only 30% of the energy released by the gas goes into heating the water, we can calculate the total energy released by the gas using the formula:

Total energy released = Heat required to boil water / 0.3

Calculation:

Total energy released = 664,000 J / 0.3

Result:

The total energy released by the gas to boil the water is approximately 2,213,333 J.