copper (2) nitrate will be used in a lab. What is one way copper (2) nitrate can be produced?

Also, my other question is my classmate claims that the products of a chemical reaction can never be changed but is my classmate correct? why ??

I prefer to write that as copper(II) nitrate. That can most easily be produced with copper metal and nitric acid.

Your classmate is El Wrongo!.
I can take AgNO3 and react it with KCl to produce AgCl and KNO3. I can separate those compounds and react either or both with something else to make whatever I wish.

One way to produce copper (II) nitrate is by reacting copper metal with nitric acid. Here's a step-by-step explanation of the process:

1. Start by measuring and preparing the required materials: copper metal (usually in the form of copper wire or copper turnings) and concentrated nitric acid (usually with a concentration of 65% or above).

2. Use proper safety measures such as wearing gloves, safety goggles, and working in a well-ventilated area. Nitric acid can be corrosive and harmful if not handled correctly.

3. In a fume hood or a well-ventilated area, place the copper metal into a suitable container that can withstand the reaction (e.g., a glass beaker or flask).

4. Carefully pour the nitric acid into the container with the copper metal. The reaction between copper and nitric acid is exothermic, meaning it releases heat and can produce nitrogen dioxide gas. The reaction can be represented by the following chemical equation:
Cu + 4HNO3 -> Cu(NO3)2 + 2NO2 + 2H2O

5. Observe the reaction as it proceeds. The copper metal will dissolve in the nitric acid, and the solution will turn blue due to the formation of copper (II) nitrate.

6. Once the reaction is complete, you will have obtained copper (II) nitrate solution. It can be further processed if necessary, such as by evaporating the water to obtain solid copper (II) nitrate crystals.

Remember to handle the chemicals with care, follow proper lab safety procedures, and consult any specific lab protocols or guidelines provided by your instructor before attempting this experiment.