Answer:
precipitate , chemical
Explanation:
a precipitate is is an insoluble solid that forms when two solutions are combined and react chemically. The two clear colorless liquids is a chemical change because a different solid substance is formed
A medium can be anything that a wave can pass through e.g the medium can be solid objects, air, water, etc.
Answer:
"The elements are arranged in seven horizontal rows,called periods or series,and 18 vertical columns,called Groups."
Explanation:
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