It’s basically that’s any system that’s closed to all transfers of matter and energy the mass of the system has to remain constant over time because they can’t change meaning you can’t add or remove from it
The minimum quantity of energy that the reacting species must possess in order to undergo a specified reaction.
Copper substance cannot be decomposed by a chemical change.
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- When heated, the copper to carbonate breaks down into copper to oxide. The copper carbonate, which is dark in colour, releases carbon dioxide as well.Because they are the simplest chemically, elements cannot be broken down by chemical processes.
- Elements are those pure compounds that cannot be broken down by reactions, heating, electrolysis, or other common chemical processes. Examples of elements are oxygen, gold, and silver. Its makeup stays the same, though. One instance of a physical change is melting. A physical change is when a sample of matter experiences a change in some of its qualities but not in its identity. Water turns into water vapour when it is heated.
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To determine whether a compound is polar or nonpolar you have to take into account:
1) formation of dipoles due to the difference in electronegativities of the atoms
2) shape of the molecule to conclude whether there is a net dipole momentum.
You already, likely, know that the electronegativities of H and O are significatively different, being O more electronegative thatn H. So, you can conclude easilty that the electrons are atracted more by O than by H, thus creating two dipoles H→O
Regarding the shape, it may appear that the molecule is symmetrical, which would lead to the cancellation of the two dipoles. But that is not the true. The H2O2 is not symmetrical.
The lewis structure just show this shape
** **
H - O - O - H
** **
which is what may induce to think that the molecule is symmetrical, leading to the misconception that it is nonpolar.
But in a three dimensional arrangement you could see that the hydrogens are placed in non symmetrical positions, which leads to the formation of a net dipole momentum, and thus to a polar molecule.
The fact that H2O2 is a polar compound is the reason why it can be mixed with water and the H2O2 that you buy in the pharmacy is normally a solution in water.
So, the hydrogen peroxide is polar because the hydrogens are not placed symmetrically in the molecule, which result in a net dipole momentum.