<span>When an atom or compound is oxidized, its properties change. For example, when an iron object undergoes oxidation, it is transformed because it has lost electrons. Unoxidized iron is a strong, structurally sound metal, while oxidized iron is a brittle, reddish powder. The diagram below illustrates what happens to an atom of iron as it is oxidized
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Chemical Reactions
Chemical changes take place when molecules or elements interact with other elements or molecules to form new chemical compounds. In order for a reaction to take place between molecules and or atoms, these molecules must come into contact with each other.
An example of a chemical reaction can be shown by the reaction of ammonia with hydrogen chloride to form ammonium chloride. This reaction is usually shown by a shorthand method called a chemical equation. The chemical equation for this reaction is...
NH3 + HCl � NH4Cl
This equation does not clearly show what has happened. In order for these two molecules to react, the pair of electrons on nitrogen must collide with the hydrogen atom of the hydrogen chloride on the side exactly opposite of the chlorine atom.
This collision must not only be precise as to the angle of the collision, it must have enough energy to break the bond between the hydrogen atom and the chlorine atom and form a new bond between the hydrogen atom and the nitrogen atom. Energy is released when a bond is formed. If all of these requirements are met, a reaction occurs forming a new compound.

The rate of a chemical reaction depends on all of the above factors. The reaction rate is measured by the change in concentration of one of the reactants or products over a measured period of time.
If some reaction condition is changed, the reaction rate will be changed.
Reaction coordinate diagrams are used to visualize the energy changes in chemical reactions. Some initial energy must be applied to any reaction in order to get the reaction started. This energy is called the energy of activation Ea.
If a reaction releases more energy than it takes to keep it going, it is called an exothermic reaction.

If a reaction requires a constant application of energy to keep it going, it is called an endothermic reaction.

A catalyst is something that, when added to a chemicalreaction, will increase the reaction rate without undergoing a permanent change. Although it appears that only Ea is lowered for a catalyzed reaction, the actual reaction pathway must change due to the involvement of the catalyst with the reactants. The energy released for the reaction remains the same. Catalysts are used extensively in biochemical reactions in order to decrease the energy demands for the animal or plant.

Matter can neither be gained nor lost in a chemical reaction. The number and type of atoms in the reactants must exactly equal the number and types of atoms in the products. The arrangement of the atoms will be different because new compounds are formed. Therefore, we must balance chemical equations with respect to the numbers of all of the atoms that are involved in the reaction.
Answer:
a) The wavelength is around 33.8 nm = 3.38*10⁻¹ nm
b) Ultraviolet
Explanation:
a) The energy (E) of a photon is related to its wavelength (λ) by the Planck's equation:
where h = Planck's constant = 6.626*10^-34 Js
c = speed of light = 3*10^8 m/s
E = 3.55*10^6 J/mol
The energy in terms of J/photon is:
Based on eq(1)
\lambda = h\frac{c}{E}=6.626*10^{-34}Js*\frac{3*10^{8}m/s}{5.89*10^{-18}J}=3.38*10^{-8}m
The wavelength is around 33.8 nm = 3.38*10⁻¹ nm
b) In the electromagnetic spectrum the ultraviolet range extends from 390 nm-8.82 nm
The calculated wavelength of 33.8 nm should fall in the UV range.
Evaporation happens<span> when atoms or </span>molecules<span> escape from the liquid and turn into a vapor. Not all of the </span>molecules in a liquid have the same energy. <span>Sometimes a </span>liquid<span> can be sitting in one place (maybe a puddle) and its molecules will become a </span>gas<span>. That's the process called </span>evaporation<span>. It can happen when liquids are cold or when they are warm. It happens more often with warmer liquids. You probably remember that when matter has a higher temperature, the molecules have a higher </span>energy<span>. When the energy in specific molecules reaches a certain level, they can have a </span>phase change<span>. Evaporation is all about the energy in individual molecules, not about the average energy of a system. The average energy can be low and the evaporation still continues. </span>
