Question

789. В бочку с водой опустили лёд массой 2 кг при тем-пературе 0 °С. Сколько воды было в бочке, если после таянияльда температура воды уменьшилась от 20 до 18°С?

Answer 1

Ответ: 180 кг

Объяснение: на фото

Answer 2

Calculation of the Amount of Water in the Barrel

To calculate the amount of water in the barrel, we need to consider the conservation of mass and energy during the process of ice melting.

Given: - Mass of ice = 2 kg - Initial temperature of water = 0 °C - Final temperature of water = 18 °C

When the ice melts, it absorbs heat from the water, causing the temperature of the water to decrease. The amount of heat absorbed by the ice can be calculated using the equation:

Q = m * L

Where: - Q is the heat absorbed or released (in joules) - m is the mass of the substance (in kg) - L is the latent heat of fusion (in J/kg)

The latent heat of fusion for water is 334,000 J/kg.

The heat absorbed by the ice is equal to the heat released by the water, which can be calculated using the equation:

Q = m * c * ΔT

Where: - Q is the heat absorbed or released (in joules) - m is the mass of the substance (in kg) - c is the specific heat capacity of the substance (in J/(kg·°C)) - ΔT is the change in temperature (in °C)

The specific heat capacity of water is approximately 4,186 J/(kg·°C).

By equating the two equations, we can solve for the mass of water in the barrel.

Let's calculate the mass of water in the barrel:

Q_ice = Q_water

m_ice * L = m_water * c * ΔT

Substituting the given values:

2 kg * 334,000 J/kg = m_water * 4,186 J/(kg·°C) * (18 °C - 0 °C)

Simplifying the equation:

668,000 J = m_water * 4,186 J/(kg·°C) * 18 °C

668,000 J = m_water * 75,348 J/(kg·°C)

Solving for m_water:

m_water = 668,000 J / (75,348 J/(kg·°C))

m_water ≈ 8.86 kg

Therefore, there was approximately 8.86 kg of water in the barrel before the ice melted.

Please note that the calculation assumes that there is no heat exchange with the surroundings and that the water and ice are in thermal equilibrium before the ice melts.