Question

Цилиндры из свинца, олова и стали массой 1 кг каждый нагрели в кипящей воде, а затем поставили на лёд. Через некоторое время часть льда под ними растаяла, и образовались лунки. - Как изменилась внутренняя энергия цилиндров? Почему? - Под каким из цилиндров растаяла большая масса льда, под каким меньшая? Почему? * тема: расчёт количества теплоты при нагревании и охлаждении.

Answer 1

Учитывая формулу Q=c*m*(t2-t1)? а также, что m и (t2-t1) для цилиндров одинаковые, то:
Больше растает льда под свинцовым цилиндром, а меньше всего под оловянным ( удельные теплоемкости разные).
Внутренняя энергия при остывании уменьшается за счет теплообмена со льдом.

Answer 2

The Change in Internal Energy of the Cylinders

When the cylinders made of lead, tin, and steel, each weighing 1 kg, were heated in boiling water and then placed on ice, the internal energy of the cylinders changed. The change in internal energy can be attributed to the transfer of heat between the cylinders and their surroundings.

When the cylinders were heated in boiling water, they absorbed heat from the water, causing their internal energy to increase. This increase in internal energy is due to the heat transfer from the higher temperature water to the lower temperature cylinders. The heat transfer occurs until thermal equilibrium is reached, meaning the temperature of the cylinders becomes equal to the temperature of the water.

When the heated cylinders were placed on ice, heat transfer occurred again, but this time in the opposite direction. The cylinders transferred heat to the ice, causing the ice to melt and form cavities or depressions underneath the cylinders. This heat transfer resulted in a decrease in the internal energy of the cylinders.

The change in internal energy of the cylinders can be calculated using the equation:

ΔU = Q - W

Where: - ΔU is the change in internal energy - Q is the heat transferred to or from the cylinders - W is the work done by or on the cylinders

In this case, since the cylinders are not performing any work, the equation simplifies to:

ΔU = Q

Therefore, the change in internal energy of the cylinders is equal to the heat transferred to or from the cylinders.

The Mass of Ice Melted under Each Cylinder

The mass of ice melted under each cylinder depends on several factors, including the thermal conductivity of the material and the initial temperature difference between the cylinders and the ice.

The thermal conductivity of a material determines how well it conducts heat. Materials with higher thermal conductivity transfer heat more efficiently. In this case, the thermal conductivity of lead is lower than that of steel, and the thermal conductivity of steel is lower than that of tin. Therefore, the lead cylinder would transfer heat less efficiently to the ice compared to the steel and tin cylinders.

Additionally, the initial temperature difference between the cylinders and the ice also plays a role. The larger the temperature difference, the more heat will be transferred. If the lead cylinder had a smaller initial temperature difference compared to the steel and tin cylinders, it would transfer less heat to the ice, resulting in a smaller mass of ice melted underneath it.

Therefore, it is likely that the larger mass of ice melted would be under the steel or tin cylinder, while the smaller mass of ice melted would be under the lead cylinder.

Please note that the exact calculations for the mass of ice melted would require specific values for the thermal conductivity of the materials and the initial temperature difference, which are not provided in the question.