If 100 g of water at 80°C is mixed with 200 g of water at 20°C, what will be the

Practice Questions

Q1
If 100 g of water at 80°C is mixed with 200 g of water at 20°C, what will be the final temperature?
  1. 30°C
  2. 40°C
  3. 50°C
  4. 60°C

Questions & Step-by-Step Solutions

If 100 g of water at 80°C is mixed with 200 g of water at 20°C, what will be the final temperature?
  • Step 1: Identify the masses and temperatures of the two water samples. We have 100 g of water at 80°C and 200 g of water at 20°C.
  • Step 2: Use the formula for the final temperature (Tf) when mixing two bodies of water: (m1 * T1 + m2 * T2) / (m1 + m2).
  • Step 3: Plug in the values: m1 = 100 g, T1 = 80°C, m2 = 200 g, T2 = 20°C.
  • Step 4: Calculate the total energy from both water samples: (100 g * 80°C) + (200 g * 20°C).
  • Step 5: Calculate the total mass: 100 g + 200 g = 300 g.
  • Step 6: Now calculate the final temperature: (8000 + 4000) / 300 = 12000 / 300 = 40°C.
  • Step 7: Conclude that the final temperature of the mixed water is 40°C.
  • Conservation of Energy – The principle that energy cannot be created or destroyed, only transferred, which is applied here to find the equilibrium temperature of mixed water.
  • Heat Transfer – Understanding how heat flows from the hotter water to the cooler water until thermal equilibrium is reached.
  • Specific Heat Capacity – The concept that different substances require different amounts of energy to change temperature, though in this case, both substances are water.
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