You'll mix food coloring with water at two different temperatures. Measure and pour 1/2 cup of hot water from the faucet into a glass. Then measure and pour 1/2 cup of cold water from the faucet into the other glass. Hold the dropper of food coloring just above the surface of water, and carefully add one drop in the center of each glass. Wait a few minutes and then look at the glasses from the side. Place the white piece of paper behind the glasses to make it easier to see. What do you observe? Is there a difference in how it mixes?

It is widely assumed that people need to engage in intellectual activities such as solving crossword puzzles or mathematics problems in order to maintain mental sharpness as they age. in fact, however, simply talking to other people—that is, participating in social interaction, which engages many mental and perceptual skills—suffices. evidence to this effect comes from a study showing that the more social contact people report, the better their mental skills. which of the following, if true, most seriously weakens the force of the evidence cited? (a) as people grow older, they are often advised to keep exercising their physical and mental capacities in order to maintain or improve them. (b) many medical conditions and treatments that adversely affect a person's mental sharpness also tend to increase that person's social isolation. (c) many people are proficient both in social interactions and in solving mathematical problems. (d) the study did not itself collect data but analyzed data bearing on the issue from prior studies. (e) the tasks evaluating mental sharpness for which data were compiled by the study were more akin to mathematics problems than to conversation.