Answer:
The hydrogen atom has just one electron, but many spectral lines. However it contains many shells and the movement of that electron from one shell to another causes the release of energy and also an emission of photons.
A spectral line are dark or bright lines formed within a specific frequency range which differ from other frequencies.Because of the difference of energy for the various shells, it produces different wavelengths and this is the reason for the many spectral line for hydrogen.
The complete chemical reaction of aqueous Sodium sulfate and aqueous Barium nitrate is

The right side and the left side of the reaction have equal number of elements, therefore it is balanced.
Answer:
C. If it is tested and the evidence does not support it.
Explanation:
A hypothesis is more less a scientific guess. Before such a guess or prediction is made, empirical observations and deductions are first made. It is from the result of the observations that a hypothesis statement is made.
For a hypothesis to become widely adopted and accepted, it must be testable within the limits of the experiment as described by the proposer. When subjected to test and it agrees, the status of a hypothesis can be upgraded.
If the hypothesis is tested and evidence contrasts the result being sort for, a hypothesis will be discarded.
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1. Physical
2. Chemical
3. Physical
4. Physical
5. Chemical
6. I really don't feel like doing 6, sorry.
7. False: energy to mass
11. False: change to exothermic
12. False: change to endothermic