Chemical change<span> is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical:</span>
<span>iron rusting (iron oxide forms)gasoline burning (water vapor and carbon dioxide form)eggs cooking (fluid protein molecules uncoil and crosslink to form a network)bread rising (yeast converts carbohydrates into carbon dioxide gas)milk souring (sour-tasting lactic acid is produced)suntanning (vitamin D and melanin is produced)</span>
Physical change rearranges molecules but doesn't affect their internal structures. Some examples of physical change are:
<span>whipping egg whites (air is forced into the fluid, but no new substance is produced)magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves).<span>boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H2O.)</span>dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.)dicing potatoes (cutting usually separates molecules without changing them.)</span>
Classification of real processes can be tricky. Complex changes can be broken down into many simpler steps. Some of the steps are chemical and others are physical, so the overall process can't cleanly be placed in either category. For example, boiling coffee involves chemical change (the delicate molecules that give coffee its flavor react with air and become new, bitter-tasting substances) and physical change (the water in the coffee is going from liquid to gaseous form.)
i guess its e) Mn (VII)
if it was wrong pls let me knw
Answer:
<u>The deviations are :</u>
- <u>The activation energy which changes with temperature</u>
- <u>The arrhenius constant which depends on the temperature</u>
Explanation:
- There are deviations from the Arrhenius law during the glass transition in all classes of glass-forming matter.
- The Arrhenius law predicts that the motion of the structural units (atoms, molecules, ions, etc.) should slow down at a slower rate through the glass transition than is experimentally observed.
- In other words, the structural units slow down at a faster rate than is predicted by the Arrhenius law.
- <em>This observation is made reasonable assuming that the units must overcome an energy barrier by means of a thermal activation energy. </em>
- The thermal energy must be high enough to allow for translational motion of the units <em>which leads to viscous flow of the material.</em>
- Both the Arrhenius activation energy and the rate constant k are experimentally determined, and represent macroscopic reaction-specific parameters <em>that are not simply related to threshold energies and the success of individual collisions at the molecular level. </em>
- Consider a particular collision (an elementary reaction) between molecules A and B. The collision angle, the relative translational energy, the internal (particularly vibrational) energy will all determine the chance that the collision will produce a product molecule AB.
- Macroscopic measurements of E(activation energy) and k(rate constant ) <em>are the result of many individual collisions with differing collision parameters. </em><em>They are averaged out to a macroscopic quantity.</em>
1 mole ------------- 6.02 x 10²³ atoms
0.70 moles -------- ( atoms platinum )
atoms platinum = 0.70 x ( 6.02 x 10²³ ) / 1
= 4.2 x 10²³ atoms platinum
hope this helps!
