Several weeks after Allen conducted a classroom experiment on the effectiveness of various metals in releasing hydrogen gas from hydrochloric acid, he read that the gas company was burying sheets of magnesium next to iron pipelines in order to prevent rusting. Allen wondered if other active metals would also be effective in preventing rust. To investigate, he placed each of the following into a separate test tube containing water: one iron nail; one iron nail wrapped with an aluminum strip; one iron nail wrapped with a magnesium strip; and one iron nail wrapped in a lead strip. He used the same amounts of water from the same source, equal amounts of the metal wraps and the same type of iron nails. At the end of five days, he described the amounts of rusting either as small, moderate or large. He also recorded the color of the water. Scenario B In science class, Michaela was studying the vascular system of plants. She cut the bottom off a stalk of celery and then placed the celery in colored water. She left the celery in the cup for 24 hours. When she observed the celery, she noticed that there were colored tubes in the celery stalk, which she knew was the xylem tissue. She cut off a piece of the celery and observed it under a dissecting microscope and drew her observations. 1. Describe how these two investigations are similar and how they are different. 2. Identify the test (independent), outcome (dependent) and control variables in Scenario A