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

To solve this problem you need to know the specific heats of Iron and water.

The specific heat of…
Iron: 0.45 Joules per gram per °C
Water: 4.184 Joules per gram per °C

The total energy released by the system (Iron engine and water) is equal to:
Q = (m_1 * c_1 * (delta T)) + (m_2 * c_2 + (delta T))
Where m_1 and m_2 are the masses of the Iron engine and water, c_1 and c_2 are the specific heats of Iron and water, and (delta T) is the change in temperature the two substances experience. Q is the total heat energy released.

We are given:
Q = 4.4 E6 Joules
m_1 = mass of engine = 2.5 E2 kg = 2.5 E5 grams
(delta T) = (35 °C - 10 °C) = 25 °C
And we are assumed to know the specific heats (listed above).

We do not know, and are trying to solve for, the mass of the water = m_2.

We can plug in values into the above equation for t he total energy lost by the system to get:
Q = (m_1 * c_1 * (delta T)) + (m_2 * c_2 + (delta T))
(4.4 E6 Joules) = (2.5 E5 g)*(0.45 J/g°C)*(25 °C) + m_2(4.184 J/g°C)*(25 °C)
(1587500 J) = energy lost by water = m_2(4.184 J/g°C)*(25 °C)
Now solving for m_2,
m_2 = (1587500 J) / (4.184 J/g°C)*(25 °C)
m_2 = 15177 grams of water
m_2 = 15.2 kg of water

http://www.csun.edu/~jte35633/worksheets/Chemistry/16-1SpecificHeat.pdf

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.

Answer 3

Cast Iron Cars