I read this background article the other day: If a solution has a higher concentration of hydronium ions than pure water, it has a pH lower than 7. A solution with a pH lower than 7 is called an acid . As the hydronium ion concentration increases, the pH value decreases. Therefore, the more acidic a solution is, the lower its pH value is. Did you ever taste vinegar? Like other acids, it tastes sour. Stronger acids can be harmful to organisms. For example, stomach acid would eat through the stomach if it were not lined with a layer of mucus. Strong acids can also damage materials, even hard materials such as glass. I am facing a new situation today: Mike is studying chemistry for his exam. Today, he is studying the properties of acids. He picks up an acid solution that he labels as solution A. To compare it with another solution he chooses a solution that is not an acid. He labels it as solution B. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Would solution B have less or more hydronium ions than solution A?
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Answer: less

I read this background article the other day: Rain dissolves fertilizer in the soil. Runoff carries it away. The fertilizer ends up in bodies of water, from ponds to oceans. The nitrogen is a fertilizer in the water bodies. Since there is a lot of nitrogen it causes algae to grow out of control. Figure below shows a pond covered with algae. Algae may use up so much oxygen in the water that nothing else can grow. Soon, even the algae die out. Decomposers break down the dead tissue and use up all the oxygen in the water. This creates a dead zone. A dead zone is an area in a body of water where nothing grows because there is too little oxygen. There is a large dead zone in the Gulf of Mexico. You can see it Figure below . I am facing a new situation today: Leaf farm and Plum farm provided the neighboring counties with quality produce year-round. plum farm used conventional farming methods such as fertilizer and pesticides, while Leaf farm used alternative eco-friendly methods only. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which farm caused fewer algae to grow out of control?
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Answer: Leaf

I read this background article the other day: Noble gases are also used to fill the glass tubes of lighted signs like the one in the Figure below . Although noble gases are chemically nonreactive, their electrons can be energized by sending an electric current through them. When this happens, the electrons jump to a higher energy level. When the electrons return to their original energy level, they give off energy as light. Different noble gases give off light of different colors. Neon gives off reddish-orange light, like the word "Open" in the sign below. Krypton gives off violet light and xenon gives off blue light. I am facing a new situation today: There are two signs in a bar that use noble gases to light them. Sign A and Sign B are both the same solid color and patrons always point them out as they are rather amusing signs. However, one customer has just come up to the owner and told him that Sign B has just turned off. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which sign currently has electric current flowing through it?
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Answer:
Sign A