How much firewood needs to be burned to heat 2 liters of water (temperature 20 degrees) to a boil

How much firewood needs to be burned to heat 2 liters of water (temperature 20 degrees) to a boil (100 degrees), poured into an aluminum pot weighing 600 grams 2. everything is the same, but if the efficiency of firewood is 60%

1) You must first calculate how much heat the water must receive in order to heat up from a temperature of 20 degrees to a temperature of 100 degrees according to the formula: Q = m • c • Δt. The mass of water can be found through the formula: m = ρV, where the density of water is ρ = 1000 kg / cubic meter, and the volume V = 2 liters = 2 cubic dm = 0.004 cubic meters. We get the mass m = 2 kg (1 kg of water takes up a volume of 1 liter). Specific heat capacity of water c = 4200 J / (kg • deg), temperature change Δt = 100 – 20; Δt = 80 degrees. We get Q = 2 kg • 4200 J / (kg • deg) • 80 deg = 672000 J.
2) In order to calculate how much heat will be taken by an aluminum pot when heated from a temperature of 20 degrees to a temperature of 100 degrees, we will use the formula: Q = m • c • Δt. Pot weight m = 600 g = 0.6 kg. Specific heat of aluminum c = 920 J / (kg • deg), temperature change Δt = 80 degrees. We get Q = 0.6 kg • 920 J / (kg • deg) • 80 deg, Q = 44160 J.
3) Total needed for water and pot Q = 672000 J + 44160 J = 716160 J.
4) To calculate how much firewood needs to be burned in order to heat water to a boil poured into an aluminum pot, we use the formula for calculating the heat released during fuel combustion: Q = q • m, then the mass of the fuel is m = Q: q, where the specific heat of combustion firewood q = 10 MJ / kg. We will assume that all the released heat is transferred to the pot with water m = 716160 J: 10000000 J / kg = 0.0716 kg.
5) If the efficiency of firewood = 60%, then Q = 0.6 • q • m, m = Q: (0.6 q) = 716 160 J: 6 000 000 J / kg = 0.0716 kg = 0.1194 kg.
Answer: 0.0716 kg and 0.1194 kg.