Problem: I read this background article the other day: Circadian rhythms are regular changes in biology or behavior that occur in a 24-hour cycle. In humans, for example, blood pressure and body temperature change in a regular way throughout each 24-hour day. Animals may eat and drink at certain times of day as well. Humans have daily cycles of behavior, too. Most people start to get sleepy after dark and have a hard time sleeping when it is light outside. In many species, including humans, circadian rhythms are controlled by a tiny structure called the biological clock . This structure is located in a gland at the base of the brain. The biological clock sends signals to the body. The signals cause regular changes in behavior and body processes. The amount of light entering the eyes helps control the biological clock. The clock causes changes that repeat every 24 hours. I am facing a new situation today: Jason is an average guy who goes to work each day, lives in an apartment, exercises sometimes, goes out and drinks some weekends and just generally enjoys life. Brad, however, has chosen to live in a dark cave that has no windows. He lives in a cave that has almost no light except for some candles he lights from time to time. If he needs food or supplies, he pays someone to go get them, and they slide them through a hole that can open in the steel door at the entrance of the cave. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Who is less likely to eat meals at the same time each day?

A: Brad

Problem: I read this background article the other day: Electronegativities generally increase from left to right across a period. This is due to an increase in nuclear charge. Alkali metals have the lowest electronegativities, while halogens have the highest. Because most noble gases do not form compounds, they do not have electronegativities. Note that there is little variation among the transition metals. Electronegativities generally decrease from top to bottom within a group due to the larger atomic size. I am facing a new situation today: John was studying the periodic table. To make things easier for him he divided the table in different sections, section A, section B, section C, and section D. Section A elements are located at the left of the table, but section B elements are located at the right side of the table. Section C elements are located at the top, but section D elements are located at the bottom. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Would section B have more or less electronegativities than section A?

A: more

Problem: I read this background article the other day: Some materials have negative heats of solution; the dissolution of one of these solutes in water is an exothermic process. Heat is released, causing a net increase in the temperature of the solution. Conversely, other substances have positive heats of solution. For example, the dissolution of potassium nitrate in water is an endothermic process. The resulting absorption of energy causes the solution to become colder. Calculations involving heats of solutions follow the same basic approach that we have used with other enthalpy problems. I am facing a new situation today: John is conducting an experiment in his chemistry lab. His goal is to find a chemical solution that can regulate temperature. To that end, he considered two processes, process A and process B. Process A is an exothermic process, but process B is an endothermic process. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: In which process the solution would be warmer, process A or process B?

A: process A

Problem: I read this background article the other day: Each radioactive isotope has a characteristic decay time periodthe half-lifethat is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth. I am facing a new situation today: David was working in his chemistry lab. He selected two isotopes, sample A and sample B. Sample A had longer half-life, but sample B had shorter half-life. After some time he checked sample A when its one half-life had passed. He noted it as sample A1. Then he came back to see it again when two half-lives had passed. He noted it as sample A2. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Would sample A have less or more isotopes than sample A1?

A:
more