why does water come out of a cars tailpipe when you start it in the morning?

Question

my 9 yr old nephew asked me once..."why does water drip out of a newly started car in the morning, I say its condensation in the exhaust sytem am I right or is there a better answer... thanks.

Answer 1

You are half right.
There is condensation present in the exhaust, and in the morning, before the exhaust is warm enough to cause it to become a vapor cloud, it will drip out the pipe, pushed out by the exhaust pressure.
But, in addition, there is moisture in the air that the engine uses, and it will also be present in the exhaust stream.
In addition to all of this, the natural result of combustion in the cylinders is a chemical change.
In the chemistry of the combustion, there is nitrogen in the air, along with oxygen.
Also in the fuel, there are hydrocarbons.
When there is heat added (spark) the chemical change is (in perfect combustion) carbon DIoxide and di-Hydrogen Oxide (H2O).
Until the exhaust components become hot enough for this to be pure vapor, it is seen as a drip, along with the condensation. As it warms up, the drip becomes steam, and then, ultimately, superheated steam or water vapor.

Happy Motoring

Answer 2

The burning of fuel (a hydrocarbon) in the engine's cylinders produces,as by-products ,Carbon dioxide and water vapour (due to the very high temperature of the combustion chambers of the car).

In the morning the temperature of the exhaust system is STILL cold (atmospheric temperature) at the start.

The water vapour thus condenses as liquid water which comes out of the tailpipe.

After some time the temperature of the exhaust system rises to above 100 Celsius and once this is reached the condensation stops and the water vapour comes out as a gas.

Answer 3

Yes, When you turn off the engine air is drawn into the exhaust pipe and the water in the air condenses. This water is then blown out with the exhaust next time the engine is started.

Answer 4

You're right - condensation in the exhaust pipe.

More specifically, water vapor is created when the fuel in the car burns. The warm warm moist air then travels out the exhaust pipe. When it hits cooler air or the cooler pipe itself, the water in the warm air changes from the vapor state to the liquid state, forming water drops along the walls of the pipe, which then drip off.

At age 9 your nephew may have learned about chemical changes (as opposed to physical changes) and may or may not have learned about phases of matter. This is a great opportunity for you to reinforce the material he is learning in school and show how it relates to reality. :)

Answer 5

The water from the combustion process condenses on the cold metal of the exhaust system when the engine is started. Once, the pipes are hot the consensation is gone.

Answer 6

It is condensation from the moisture in the air that has built up in the exhaust system overnight, and is being burned off as water from the heat of the engine running.

Answer 7

You are right.It is normal for a car to drip some fluid out of the tailpipe when first started and for several minutes afterwards. The fluid is condensation (water) that occurs. Sometimes, it can pick up some black soot from the tailpipe, which would give it a dark color.

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Answer 8

One of the byproducts of combustion is water vapor. It condenses in the cold pipes.

Answer 9

condensation

Answer 10

Yes you are correct.