A 2.50*10^2-kg cast-iron car engine contains water as a coolant. Suppose that the engine's temperature is ...

Question

A 2.50*10^2-kg cast-iron car engine contains water as a coolant. Suppose that the engine's temperature is 35.0º Celsius when it is shut off, and the air temperature is 10.0º Celsius. The heat given off by the engine and water in it as they cool to air temperature is 4.40*10^6 Joules. What mass of water is used to cool the engine?

Please help me with this problem.
I can't understand this.

Answer 1

Okay, you're missing some information here. You need to know the specific heat of cast iron to answer this problem. Luckily, I know that it is 0.46J/g°C, so we can get started.
First, you need the temperature that the engine changes. That is 35°C-10°C, which is 25°C. Now we find out how much heat the cast iron gave off.
2.5*10^2kg=2.5*10^5g
(2.5*10^5g)(25°C)(.46J/g°C)=2....
Now we subtract that from the total energy that was released by the water and the engine.
4.40*10^6J-2.875*10^6J=1.525*1...
Now we solve for the mass of the water using the specific heat, temperature change, and the heat released that I just calculated.
1.525*10^6J=(25°C)(4.184J/g°C)... of grams)
1.525*10^6J=1.046J/g * # of grams
Divide both sides by 1.046J/g and you get:
1.458*10^4g = #of grams
Convert to Kg:
14.58kg
And since the conditions you gave all had 3 significant figures, round the answer to 3 significant figures:
14.6kg

Hope this helps!!!

Answer 2

It's not necessarily a broken line. When a car overheats, the coolant expands, and at a critical point it comes out the overflow valve at the top of the coolant tank, and creates steam. And if there was no coolant in the tank, it was likely an overheating. However, putting more coolant in it isn't enough, because once coolant overheats and boils over, air gets trapped in the radiator and inhibits the cooling of the engine, which just leads to further overheatings. It could be just a random overheating due to low coolant, but it also could be a more serious problem such as a head gasket, cooling fan, or water pump. I'd definitely recommend taking it to the mechanic and getting it checked out. They can tell you what's wrong for sure.