Of the steps included in the scientific method, Shameka is performing step five, which is to<u> test your hypothesis by performing an experiment</u>.
The scientific method is the globally accepted process by which to make scientific claims. This method includes seven steps which are:
Ask a question
Do research
Create a hypothesis
Design an experiment to test the hypothesis
Perform the experiment
Study the results and make a conclusion
Communicate the results to your peers.
The question states that Shameka is <u>gathering samples from nearby water sources</u>, therefore she is in the process of testing her hypothesis through experimentation, which corresponds to step 5 of the scientific design.
A change in the color of a substance -- this one is indeed a chemical change. Think of iron, if iron turns reddish, it's a completely different substance.