In physics and chemistry, the law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as the system's mass cannot change, so quantity can neither be added nor be removed. Therefore, the quantity of mass is conserved over time.
The law implies that mass can neither be created nor destroyed, although it may be rearranged in space, or the entities associated with it may be changed in form. For example, in chemical reactions, the mass of the chemical components before the reaction is equal to the mass of the components after the reaction. Thus, during any chemical reaction and low-energy thermodynamic processes in an isolated system, the total mass of the reactants, or starting materials, must be equal to the mass of the products.
The concept of mass conservation is widely used in many fields such as chemistry, mechanics, and fluid dynamics. Historically, mass conservation was demonstrated in chemical reactions independently by Mikhail Lomonosov and later rediscovered by Antoine Lavoisier in the late 18th century. The formulation of this law was of crucial importance in the progress from alchemy to the modern natural science of chemistry.
The conservation of mass only holds approximately and is considered part of a series of assumptions coming from classical mechanics. The law has to be modified to comply with the laws of quantum mechanics and special relativity under the principle of mass-energy equivalence, which states that energy and mass form one conserved quantity. For very energetic systems the conservation of mass-only is shown not to hold, as is the case in nuclear reactions and particle-antiparticle annihilation in particle physics.
Mass is also not generally conserved in open systems. Such is the case when various forms of energy and matter are allowed into, or out of, the system. However, unless radioactivity or nuclear reactions are involved, the amount of energy escaping (or entering) such systems as heat, mechanical work, or electromagnetic radiation is usually too small to be measured as a decrease (or increase) in the mass of the system.
For systems where large gravitational fields are involved, general relativity has to be taken into account, where mass-energy conservation becomes a more complex concept, subject to different definitions, and neither mass nor energy is as strictly and simply conserved as is the case in special relativity.
conservation of mass and energy?
ok... i get the principle, but what about birth? Meaning what about when someone is born, where is that mass coming from? Where is the energy coming from? The only thing i can think of is the nurishment the mom takes and gives to the baby, but how can that...
:smile: Hi all
I am in deperate, desperate, desperate need of some help. I have this question that I have been working on for hours and have made no progress at all.
Here is the question.
Write down the "conservation of mass" equation for dm(r)/dr, where m(r) is the mass inside radius...
Suppose I burned a log. If I collected all the products of the burning process (the smoke particles, the ashes, etc.) would they have the same exact mass as my original log? Or would they have less mass because they are at a lower energy state then the original log (Energy-mass equivalence)...
with relativistic concepts in mind
A Kaon split into 2 pions, One pion is stationary and one is stil moving in the same direciton.
For Kaon rest mass = 497.67MeV/c^2
Pion = 139.57MeV/c^2
What is the kineric energy of the kaon and what is the energy of hte pion not at rest.
Since...
Hi. This was the one extra problem credit problem I couldn't figure out in our momentum unit. (Since its not homework I posted here)
In a fireworks display, a 3.0 kg rocket moving at 4 km/h straight up explodes into three equal pieces of of 1.0 kg in mass. Piece A moves straight...