Why does mass appear to be conserved durring a chemical reaction?

Answer 1

Complex question.

First, mass does not appear to be conserved, it is conserved. There are 3 things that are conserved, they are mass, energy and momentum. If you add up the mass of each element for a given reaction, it will be equal. This can be hard to understand though especially in a classroom lab. Take the burning of wood. If you light a piece of wood on fire and let it burn for a while and collect the ashes it should weigh more than it did before you burnt it. Why? Because you added oxygen molecules to the wood from the air, but you did not measure the oxygen when you weighed it before. This can also be a bad example for the fact that while you are burning the wood, water from the wood is vaporizing into the atmosphere therefore losing mass.

The only way mass alone is not conserved is in a nuclear reaction, but if you include an energy balance along with a mass balance the equations will equalize out. E=mc^2.

Answer 2

Actually, it does NOT appear to be conserved. That's why it had to be carefully studied and tested before the "law of conservation" was accepted. Mass is not conserved, since energy is usually released or consumed in a chemical reaction. It is the sum of mass and energy that is preserved.

Answer 3

because matter is neither created or destroyed this assumes no gas is released