ACT Science Practice Test - 3 - online test

Many of the household products we use, as well as various foods, are either acidic or basic, however, we can only consume those foods which are weakly acidic or basic. If we ingest strong acids or bases, such as some chemical cleaning solutions, we could compromise our health and even die. Water is made up of acids (H+, hydrogen ions) and bases (OHB, hydroxide ions), and its formula is H2O. In pure water, the number of H+ ions is equal to the number of OHB ions. When a substance has more H+ ions it is an acid and conversely, when a substance has more OHB ions it is base.

We use pH (the power of hydrogen) to measure the concentration of a substance; to know how acidic or basic is the substance. Put another way, pH measures the amount of H+ and OHB ions. We use the pH scale, which ranges from 0B14 to classify acids and bases. Pure water is neutral with a pH of 7. pH values below 7 are acidic (0 being the strongest acidity) and those above 7 are basic (14 being the strongest basicity). pH is measured with either indicator paper, which is treated with chemical indicators that vary in colour according to pH, or a pH meter, which is an electronic device with an attached probe. The probe contains an acidic solution covered by glass that measures the migration of H+ ions across it. The probe is inserted into an unknown solution and if this solution has a different pH than the solution in the probe, an electric potential results, which is registered on the meter.

Andrea and Ryan are partners in their chemistry lab and their TA had assigned them a project on acids and bases last week. For their first experiment they determined the pH of various items using a pH meter. For their second experiment, they determined the equivalence points of mixed acidic and basic solutions. They added either a strong base or acid, drip by drip, to another strong acid or base, respectively. After each drip was added, they measured the pH of the solution and recorded the value. Titration curves were graphed for each dyad of solutions to determine the equivalence point (see Figure 1 which is an example of one of their titration curves). The equivalence point is when the two solutions have been mixed in exactly equal proportions of acid and base. Titration curves not only show you the equivalence point, but also what volume of solution is needed to turn an originally acidic or basic solution into a basic or acid solution, respectively. For example, as a strong base is slowly added to a strong acid, the acidic solution gradually becomes a weak acid and then a weak base and finally a strong base (Figure 1).

Science lesson Science Practice Test 3 exam questions 1. question pragraph

Science lesson Science Practice Test 3 exam questions 1. question pragraph

Andrea had an unknown solution and she wanted to know if it was an acid or a base. She used a pH meter to measure the concentration of ions in the solution. The result was a pH of 8. What was her conclusion?

The solution is acidic.

The solution is basic.

The solution is neutral.

The results are inconclusive.

See supporting documentation. A solution with a pH of 8 is basic.

Ryan measured the pH of strawberries by first puréeing them in a blender. He then used a pH meter to test the pH of the purée. What was the pH of the strawberry purée?

13

3.5

1

7.5

You would probably assign the taste of strawberries (in terms of sour taste) to be somewhere between lemons and tomatoes, therefore (according to Table 1) they are acidic (below a pH of 7). The pH level 3.5 is the most logical answer. Strawberries cannot have a pH of 7.5 because that is close to the pH of pure water, which does not taste either bitter or sweet. Pure acid and battery acid have a pH of 0 and 1, respectively. We cannot ingest these items, therefore their pH is too low for strawberries. Lye and sodium hydroxide have a pH of 13 and 14, respectively, and we cannot ingest those either so their pH is too high for strawberries.

Andrea and Ryan’s TA gave them some household items so that they could test the pH values. One of these items was in the form of a solution and they had no idea what it was. The only information they were given was that it was a food item and they could see that the solution was a reddish color. They tested the pH, which was found to be 4.6. What is the best answer for what this solution could be?

tomatoes

red wine

cherry cola

strawberry milk

See Table 1. Tomatoes have a pH of 4.5. Cola has a pH of 3, wine a pH of 4, and milk a pH of 6.5.

In Figure 1, what volume of base was needed to reach the equivalence point?

8.9 mL

8.3 mL

9 mL

8 mL

The vertical dotted line is lined up with 8.3 mL of base added on the X axis.

Ryan and Andrea drew a graph showing a titration curve for a strong base added to a strong acid. Which star represents the equivalence point?

A

C

D

B

See Figure 1 and supporting documentation. The documentation says, “The equivalence point is when the two solutions have been mixed in exactly equal proportions of acid and base.” The acid used had a pH of 0 (beginning of the curve, at the bottom) and the base added to it had a pH 14 (end of the curve, at the top). Therefore, equal proportions of each would be a pH of 7 (same as in Figure 1).

A strong acid is added to a strong base and a titration curve is plotted. What should the graph look like?

Science lesson Science Practice Test - 3 exam questions 6 question 1 Answer

Science lesson Science Practice Test - 3 exam questions 6 question 2 Answer

Science lesson Science Practice Test - 3 exam questions 6 question 3 Answer

Science lesson Science Practice Test - 3 exam questions 6 question 4 Answer

The beginning of the curve is at pH 14 and the end of the curve is at pH 0. B occurs when a weak acid is added to a weak base. C is when a strong base is added to a strong acid. D is when a weak base is added to a weak acid.

Living in groups can be beneficial and costly at the same time. Animals have to make decisions about whether they want to live in a group or not and they weigh the benefits against the costs. Two benefits of group living are decreased predation risk and increased foraging efficiency. In other words, living in groups provides protection from predators because it is easier to catch an individual that is alone compared to one that is part of a group and being part of a group means that there are more eyes watching for predators. Living in groups also makes it easier to find food as there are more eyes searching for food at the same time.

In addition to these benefits, there are costs of living in groups, such as increased predation risk and increased competition for food. In other words, predators may spot a group more easily than a lone individual because a group is larger and more visible from a distance. When the group finds food, there are more individuals around to share in the resources and so competition is higher in groups.

Two main hypotheses have been proposed as possible mechanisms driving grouping behavior: predation risk and activity budgets. Individuals in groups also assort phenotypically, such as by species, body size, age, and sex, to further increase the benefits and decrease the costs of group living. Explanations for phenotypical assortment can be found within the main hypotheses regarding grouping in general.

Scientist 1 explains assortment in the context of the predation risk hypothesis, whereas Scientist 2 explains it in the context of the activity budget hypothesis.

Scientist 1 Odd-looking individuals are usually different in color, size or behavior. The oddity effect hypothesis states that odd-¬‐looking individuals in a group are preferred and therefore, are targeted more often by predators. Odd-¬‐looking individuals are preferred because they stand out visually against the rest of the group, which makes it easier to target them for pursuit. What follows from this hypothesis is that if all individuals in the group look alike, the chance of any particular individual being targeted is reduced.

Therefore, when an animal is looking to join a group, a group where all individuals look alike should be preferred over a group that contains odd-¬‐looking individuals. In nature, group-¬‐living animals are often found in groups composed of similar-¬‐sized individuals. Predation risk (and thus the oddity effect) is one of the main reasons why animals group according to size.

Scientist 2 An activity budget is the time an individual invests in different activities such as looking for food, moving around, sticking together with the group and keeping an eye out for food and potential predators. The activity budget hypothesis suggests that grouping by similarity in size may be driven by the cost of behavioral synchrony. Behavioral synchrony is individuals keeping in sync with each other’s movements. Group living animals must synchronize their behavior or else the group will split apart causing individuals to get separated from the group and therefore, risk easily being preyed upon.

Groups in which all individuals are the same size are more synchronous in behavior than groups that contain odd-¬‐sized individuals because similar-¬‐sized individuals tend to have similar activity budgets, whereas individuals that differ in size have different activity budgets—they have different energy requirements and movement rates. The behavioral synchrony hypothesis states that different-¬‐sized individuals have to adjust when and how fast to move in order to keep in sync with the group, which can incur the cost of decreased foraging efficiency. Not being able to search and find food effectively will cause an individual to lose weight over time. They will spend more time searching and less time eating, which causes weight loss. The cost of weight loss, and thus lower fitness, may drive individuals to group by similarity in size; therefore, activity budget (and thus behavioral synchrony) is one of the main reasons why animals group by size.

According to the text, which two hypotheses specifically relate to size-assorted grouping as opposed to the overarching hypotheses regarding grouping behavior in general?

behavioral synchrony and predation risk

predation risk and activity budget

activity budget and oddity effect

oddity effect and behavioral synchrony

In the third paragraph of the passage, it is stated that predation risk and activity budget are the overarching or main hypotheses; in contrast, the oddity effect and behavioral synchrony are specific hypotheses that are discussed in the Scientist 1 and 2 sections, respectively.

For their experiments, Scientists 1 and 2 bought different-sized and different-colored minnows from PetSmart®. As soon as they got back to the lab, they measured the length and weight of each fish. They then put them randomly in schools of 10 fish. Each school was housed in a large holding tank and there were 42 holding tanks altogether. A week later, just prior to running experiments using the fish in holding tank 22, they again measured the length and weight of each fish. Both scientists noticed that the weight of some of the fish had decreased since the last time they were measured. What should they have done to prevent this from happening?

put each fish alone so it would have had all the food to itself

overfed the fish

separated the fish by color before grouping them

separated the fish by size before grouping them

The fish in each tank were of different sizes and could not sync their behavior to each other so they lost weight as a result (behavioral synchrony hypothesis).

Many benefits and costs are associated with living in groups. Which answer gives a benefit and a cost of group living?

decreased predation risk and increased foraging efficiency

decreased predation risk and increased competition for food

increased foraging efficiency and decreased competition for food

increased predation risk and decreased foraging efficiency

Decreased predation risk and increased foraging efficiency is a benefit-benefit; increased foraging efficiency and decreased competition for food is a benefit-benefit; and increased predation risk and decreased foraging efficiency is a cost-cost.

A lone small-sized zebrafish is travelling in a straight line and comes across two different schools (school 1 and school 2), each composed of 10 fish of the same species as itself. School 1 has a single large fish in it and school 2 is composed of all small fish. A shark quickly approaches and the lone fish has to make a decision as to which group to join. According to Scientist 1, this lone individual should choose which group?

school 2

the group with a single large fish

school 1

neither school

Groups composed of similarly sized fish confer greater protection from predators than those in groups composed of differently sized fish. The group with the large fish is school 1, and the oddity effect hypothesis says that odd individuals are targeted more often, which puts the whole group in greater danger so the lone fish should not join this group. Neither school is incorrect as the fish is at greater risk of predation by staying alone than by joining a grou

An orange fish is traveling through an estuary and comes across two groups of fish, one composed of 6 orange fish and 18 grey fish and the other composed of 15 grey fish and 45 orange fish. According to the oddity effect hypothesis, what is the lone fish predicted to do?

The lone fish will join the group with 15 grey fish and 45 orange fish.

The lone fish will observe which group finds food faster and join it.

The orange fish will join the group with 6 orange fish and 18 grey fish.

The orange fish will join neither group because both groups are composed of two differently colored fish.

The orange fish would be joining a group where its color is part of the majority and so would not be considered odd like the minority, therefore it benefits from decreased predation risk. The orange fish should not join the group with 6 orange fish and 18 grey fish―if the orange fish joined this group, it would be part of the minority and thus considered odd in the group and would pay a cost of increased predation risk. Although the fish could observe which group finds food faster and join it, the oddity effect is not concerned with food. The answer option suggesting that the fish should join neither group is incorrect because the oddity effect doesn’t suggest or predict that the fish will make no choice at all.

Ten trials of an experiment were run where a fish predator was put into a tank with a school of prey fish (19 brown fish, 1 blue fish). For 9 out of 10 trials, the predator targeted and attacked the odd-colored fish. Another 10 trials were run, but this time, the predator was put into a tank with a school of 19 large fish and 1 small fish. For only two of the trials, the predator targeted and attacked the odd-sized fish. For the remaining trials, the predator attacked the large-sized fish. A different predator and different prey were used for each trial. What is a possible explanation for these results?

Predation risk can explain assorted grouping in the first experiment, but not in the second.

The predator was not already full when the second experiment started so it went for the larger fish

The predator attacks small-sized fish in both experiments because they are easier to catch.

The oddity effect explains the behavior of the predator in both experiments.

The oddity effect was observed when the fish were of different colors, but not when they were of different sizes. If the oddity effect was observed with different sizes of prey, then it would be considered the driving force behind size-assorted grouping. Because this was not observed, behavioral synchrony could be the driving force behind size-assorted grouping.

A lone large-sized stickleback comes across two groups of fish in the Bow River. One group contains all large sticklebacks and the other group contains all small sticklebacks. The behavioral synchrony and oddity effect hypotheses predict that the lone stickleback will ________.

The behavioral synchrony hypothesis predicts that it will join the group of all small fish, whereas the oddity effect hypothesis predicts that it will join the group of all large fish.

The behavioral synchrony hypothesis predicts that it will join the group of all large fish, whereas the oddity effect hypothesis predicts that it will join the group of all small fish.

join the group of all large fish

join the group of all small fish

Both hypotheses have the same prediction, but for different reasons.