Explain Law of Conservation of Matter and Energy
CrazyGlue
a 4-5 page essay on this law for my chemistry class. I've searched
google and couldn't find anything, except short definitions of the law.
So can anyone give some information about the law or set up a outline
on how I should go about doing research on this law. Or what I should
do about getting started. Much is appreciated
Bob
The first thing to do is to separate this into two laws, conservation
of mass and conservation of energy. That is historically relevant, and
as a practical matter is adequate for ordinary chemistry. (I hope you
googled on them separately.)
If at some point you want to combine them, getting into the
interconversion of mass and energy, you are into the advanced physics
area of Einstein E = mc^2. It may be fun, but not easy at a HS chem
level for most. I would be inclined to suggest you not go there at
least until you have thoroughly developed the separate laws.
The separate laws should be in any chem book, and are the basis of
much that you do. If you have gotten to writing chemical equations and
doing stoichiometry problems, you know that. It is probably good to
read what different books have to say -- starting with your own book.
(If you have access to a college library, or a good bookstore, go
browse!)
If you get too many hits searching on conservation of mass, try adding
some additional terms, such as history, or phlogiston.
bob
Salmon Egg
"Bob" <bbx...@excite.XXXX.com> wrote:
Bob has given good advice. In classical physics and chemistry, before the
20th century, the conservation of energy and mass were considered to be two
separate laws. To unify them into one law requires using the principles of
special relativity. In chemistry, this shows up most prominently as
differences between actual and integral atomic mass numbers (atomic
weights). While most of those differences can be attributed to isotope
mixes, part comes from binding energy energy of nuclei.
Bill
-- Ferme le Bush
rek...@gmail.com
engineering. For example, chemical engineers commonly construct
conservation equations to describe their system. As a very simple
example of mass conservation, let's say you just have a pipe with water
flowing through:
[flow rate in (mass/time)] = [flow rate out (mass/time)]
Let's say you're filling a container but more is flowing in than out:
[flow rate in] - [flow rate out] = [accumulation]
And say you have a component 'A' flowing in and out of a container, but
'A' is also reacting in the container to form 'B', then you get the
equation for A:
[flow rate of A in] - [flow rate of A out] = [accumulation] - [rate of
disappearance of A by reaction]
The exact same things need to be done for energy (heat and work),
because let's say the reaction of A to B is exothermic. Let's also say
you're inputting work into the system because the container is being
stirred. In order to avoid an explosion, it may be necessary to remove
heat from the container by flowing cold water over the outside of the
container:
[heat removed by cold water] = [heat produced by reaction] + [work from
stirrer]
You then have to use the thermodynamic properties of water (i.e. heat
capacity) to determine the actual flow rate of water needed to keep the
container at a constant temperature.
Conservation equations like this, converted into symbols, are essential
to solving more complex engineering problems because they reduce the
number of variables when you couple them with other equations. So for
your paper outline, I'd suggest starting with basic explanation, maybe
history, and how the laws have been combined. Then you could discuss
examples of use, including stuff like above, and also apply some
examples from your chemistry class (determining the molecular weight of
an unknown compound after say a combustion reaction, styrofoam cup
calorimetry, titration). This could already be a 20 page paper.
Uncle Al
The deeply correct answer:
Google
noether homogeneity time conservation 479 hits
There is a huge heap of lightweight rationalizations to conservation
of mass-energy. There are incredibly deep mathematical roots to and
profound implications of the correct explanation. Thermodynamics
arrives later.
Note that the detonation of a fission or fusion warhead does NOT
convert mass into energy. Compared immediately before and immediately
after detonation, the numbers of protons, electrons, and neutrons are
each identical in either case. Nuclear reactions primarily alter
nuclear binding energies that have mass-equivalent via E=mc^2. Stuff
decays later. A metric kilotonne is about 46.5 mg of energy.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
Lloyd Parker
others.