How does burning a compound compare to it's reading in a spectrophotometer?

Question

for example, burning copper chloride, and also analyzing it in solution in a spectrophotometer.

Answer 1

Burning a substance (combustion) will alter it chemically.  That is, combustion represents a chemical change and the substance will no longer be in its original form.  Measuring or analyzing the substance in a spectrophotometer (in solution), normally does not alter the chemical nature of the substance.  The spectrophotometer is an analytical instrument which allows one to measure and/or monitor the concentration of a substance.