2 liters were poured into the kettle. water at a temperature of 20 degrees and put on a gas burner.

2 liters were poured into the kettle. water at a temperature of 20 degrees and put on a gas burner. 42 grams of natural gas were used to heat the water. Determine the temperature of the water if the water received 40% of the heat that can be released during the complete combustion of this gas.

Given:

V = 2 liters = 0.002 m ^ 3 – the volume of water in the kettle;

ro = 1000 kg / m ^ 3 – water density;

T1 = 20 degrees Celsius – initial water temperature;

s = 4200 J / (kg * C) – specific heat capacity of water;

m1 = 42 grams = 0.042 kilograms – the mass of gas consumed for heating water;

n = 0.4 – efficiency of the gas burner;

q = 50 * 10 ^ 6 J / kg – specific heat of combustion of gas (methane).

It is required to determine the water temperature after heating T2 (degrees Celsius).

When natural gas is burned, energy will be released:

Q = q * m1.

Of this energy, water heating will be spent:

Q1 = n * Q = n * q * m1.

Then the water temperature will be:

T2 = Q1 / (c * m) + T1 = n * q * m1 / (c * V * ro) + T1 = 0.4 * 50 * 10 ^ 6 * 0.042 / (4200 * 0.002 * 1000) + 20 = 840000/8400 + 20 = 100 + 20 = 120 degrees Celsius.

Since the boiling point of water is 100 degrees Celsius, it means that the water will be heated to a temperature of 100 degrees Celsius, and the remaining energy will be spent on converting the water into steam.

Answer: the water will be heated to a temperature of 100 degrees Celsius.