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ACT Science: Understanding & Comparing Hypotheses on Test Day

By posted December 28, 2011

You’re likely to see ACT Science questions that ask about the hypotheses on the Research Summaries passages on Test Day, although hypotheses questions can also appear in Data Interpretation and Research Summaries passages. Make sure to always examine the point of view of the student/scientist/author. Ask yourself if the data supports their conclusions, or not. You may be asked to weaken or strengthen hypotheses individually, or you may be asked to compare more than one hypothesis.

To compare them, remember that you must understand the premise behind the experiments in order to know whether the results will weaken a conclusion. Try to identify the purpose, method, and results for each experiment first to get better scores on hypotheses questions. Unless you know the purpose, method, and results and can step into the scientists’ perspectives you will have a difficult time understanding the hypotheses. Here is a harder practice ACT Science Research Summaries passage, just like you might see on Test Day!

Stars often form in large groups.  For instance, an “open cluster” such as the Pleiades may contain hundreds of stars that were formed at approximately the same time (and are thus the same age). Even larger “globular clusters” may contain a million or more stars of approximately the same age.  By observing clusters of increasing age, astronomers are able to see how the brightness and temperatures of stars change as they age.


Shortly after a group of stars forms, a plot of their brightness versus their color (the left-hand panel of Figure 1) shows that they form a diagonal line called the “Main Sequence.” The bluest stars, on the left, are the brightest, and the reddest stars, on the right, are the dimmest.  (Star colors are divided into a series of “spectral classes” – O, B, A, F, G, K – as shown on the X axis of the figure.  A star’s brightness is expressed as an “absolute visual magnitude,” with the dimmest stars having the largest magnitudes.)

Test your science skills with this ACT science practice question.

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Understanding “Variables” on the ACT

By posted December 26, 2011

Time management is crucial for great scores on the ACT Science Test. Since you only have about 5 minutes per passage, that’s less than one minute per question. Spend long enough on each passage to identify just the main information, and don’t get bogged down with the confusing details. Ignore any unknown terminology and spend most of your time on the presented data and the variables.

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A “variable” in math is a placeholder for an unknown. In ACT Science, this takes on a slightly different meaning and is used to describe the factors in an experiment.  Independent variables are factors that are controlled by the scientists. Did the scientists increase the heat in the experiment? Did they add or remove pressure? If the scientists have control over the variable, it is independent. Dependent variables are factors that the scientists observe changing. This is what the look for and how they record data — but they don’t control it.

You will also need to know direct variation and indirect variation. Direct variation occurs when two variables change in the same way over time. If Column A increases and Column B increases at the same time, we can say that the two columns vary directly.  If when Column A increases, Column B decreases, there is an indirect (also called inverse) variation between the two elements. In the real world, think of a pizza and the number of slices eaten. The weight of the pizza is inversely proportional to the number of slices eaten. That means that as more and more slices are eaten, the pizza weights less and less. In ACT Math, you may see direct and indirect variation in expression such as “y varies directly as x” or “y is directly proportional to x.” That means you can use the equation y = kx, where k is the constant of variation.

To understand the variables, look at the presented figures. Ask yourself: what does the figure tell me? What are the units of measurement? What changes, and when? In order to answer ACT Science questions correctly, you will need to pinpoint the relationships between the variables. Don’t try to memorize. Always go back to the data to find the correct answer. All of the information you need to get the questions correct are found the in passages, we just have to know where to look!

Much of the ACT Science data will be presented on graphs. Every graph has an x-axis and a y-axis. Pay close attention to the labels. The independent variable is most often found on the x-axis. When faced with multiple graphs, typically only one thing has changed. This is usually done by scientists to examine the results when a single variable is altered. If the scientists changed more than one variable, it usually doesn’t help them draw conclusions, since they wouldn’t know which change created the new results.

Remember to do the following for Data Interpretation and Research Summaries passages on Test Day:

  1. Find the Purpose, Method & Results for each experiment.
  2. Examine the data carefully, and look for the variable relationships.
  3. Go back to the passage for the correct answer.

Follow these steps on your next ACT Science passage on Grockit and you’ll soon be mastering even the most complex experiments!

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Measurements on the ACT

By posted December 22, 2011

Measurements questions on the ACT Science Test involve the numbers and corresponding labels that appear in the graphs and tables of the Science passages. Usually you will be asked to either identify the appropriate measurement, or to make an inference based on the existing numbers. To do this, pay close attention to certain statistical items: the median, range, and general distribution of the data.

Here’s another ACT science question for more practice!

The median, as you may recall from ACT Math, is the middle number when the data is ordered numerically from least to greatest. Get a sense of where the “middle” is. The range is the greatest value less the smallest value, or the span of the data. Which set has the widest range? Which has the smallest? The general distribution means how far apart each set of data is from each other. If we had a set of measurements that went 10, 20, 30, 42, 55, 65, we could say that the distribution or ratio was approximately +10  between terms. Let’s look an at example measurements question from Grockit’s database:

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ACT Math Practice: How to Graph Trigonometry Equations

By posted December 20, 2011

In order to graph trig functions, you need to understand some Trig basics. If you haven’t already, check out this quick refresher on SOHCAHTOA.

Sine, cosine, and tangent are the three main trig identities. They are usually graphed and expressed in degrees, but you may also see them expressed in radians. There are 2π radians in one circle. Each point on a circle corresponds to a certain number of radians. To convert degrees to radians, simply multiply by π/180.

Sine and cosine both have standard graphs that you need to memorize. The standard equation for sine looks like this:  y = sin x. The “period” of the wave is how long it takes the curve to reach its beginning point again. The coefficient in front of “sin” (here 1), is called the amplitude. It effects how high and how low the wave reaches vertically. If that coefficient changes, then the height changes. For example, y = 3 sin x, would show a curve that reaches +3 on the y-axis and extends down to -3 on the y-axis.

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ACT Science Practice: Conflicting Viewpoints – Understand Point of View

By posted December 16, 2011

The key to better scores on the ACT Science Test Conflicting Viewpoints passages is to hunt down each author’s point of view. As you read each passage, look closely for keywords that help you identify the author’s opinions. What does the author like? What does he criticize? What adjectives and adverbs does he use to describe the various scientific topics? He may feel positively about one thing, and negatively about another. Feel free to use smiley faces or positive and negative symbols on your ACT Science practice questions to help summarize the author’s point of view. Don’t feel like you have to take extensive, detailed notes.

Here’s an ACT science question for more practice!

If there are multiple paragraphs, remember that the scientist or student usually uses the first few sentences to introduce his topic and start a discussion of the main idea. The final paragraph wraps up the discussion and reinforces the Main Idea. If you are having trouble finding what the overall point of view is for the passage, go back to the very beginning and the very end. Here’s a sample Conflicting Viewpoints passage:

Two scientists are discussing possible origins of human life on earth.  While they agree that the earliest fossil evidence is that modern humans first appeared in Africa 130,000 years ago and there is evidence of modern humans in the Near East approximately 90,000 years ago, they do not agree on the path that led to the evolution of modern humans.  During the process of evolution, mutations of DNA appear in offspring.  While many mutations are harmful and detrimental to the individual, a few may be helpful in the survival of that individual.  DNA coding for useful traits is passed on to offspring and over very long periods of time enough of these DNA changes will accumulate for the group of organisms to have evolved into a different species.

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Unigo Expert Network: Experts Answering Your Questions

By posted December 13, 2011

The Unigo Expert Network is a group of top education experts from across the US answering questions submitted by students and parents about college admissions and succeeding after high school.

SAT. ACT. Six letters that every high school student dreads. But in the ever-changing landscape of college admissions, are standardized test scores still important? The short answer: yes. This week, our experts weigh in on just how important those scores are in comparison to the rest of your application.

“How important are standardized test scores compared to other pieces of the application?” — Chris Kim, Portland, OR

A: Test Scores Are Just One Piece of the Application

Standardized test scores are one important piece of the application. As I tell my students, “I won’t lie to you, test scores are important but they are only one piece of the puzzle.” At many state universities a GPA and/or a test score are the only admission requirements but many are realizing that other factors are just as important.  At privates colleges all factors are taken into consideration. Test scores need to be taken in context.  How well you do on a test taken early on a Saturday morning should not be the only factor in your college admission.

Maureen Lawler — College Counselor – Bishop Kelley High

 

A: Scores Get You Into Dance, But Getting Asked to Dance…

Your concern about the significance of SAT/ACT scores is well placed. College views vary on their importance, however, test scores are typically ranked third behind grades and strength of curriculum. Not all colleges view scores in the same light. Some are test optional, others allow single score choice, and still others will super score (pull the highest sub scores from different tests). Most will accept either SAT or ACT. Check college websites and consult with your school counselor. Don’t lose site of the fact that while colleges value quantitative data, it is often the qualitative information that tips their decisions.

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Drawing Conclusions on the ACT Science

By posted December 12, 2011

Most questions on the ACT Science Test will ask you to draw some sort of conclusions based on the passage. These are most like “inference” questions from the ACT Reading Test. To do this accurately, you must mark up the passages as you read, paying close attention to the topic, experiment set-ups, given results, author’s point of view, and underlying assumptions as you go. Make you to mark up the ACT test booklet you are given. Your answer grid and ACT Writing essay are the only two pieces of paper on which your score will be based. Your graders will never see the notes you made in the booklet, so feel free to draw all over it! Here’s an example of how literally “drawing” can better help you draw conclusions and get better scores on the ACT test come Test Day!

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ACT Science Practice: How to Understand “Weaken Hypothesis” Questions

By posted December 8, 2011

On the Research Summaries passages on Test Day, you may see questions that ask about the hypotheses each experiment is based on – some will ask you to weaken and some will ask you to strengthen these hypotheses. For the weaken questions, you must fully understand the set-up behind the experiments in order to know whether the results will weaken a conclusion. Try to identify the purpose, method, and results for each experiment first to get better scores on the ACT Science Test. Here is a free ACT Science practice question to start practicing for the ACT right now!

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The process of titration is an important tool in chemistry to use when trying to determine the concentration of an unknown.  While often restricted to acid and base neutralization, it can also be used in many applications when the concentration of an unknown needs to be established.  In order to use titration, one must know the concentration of one of the reactants as well as the volume of both reactants.  Normally, a chemical reaction is used in which a color change will indicate the end point of the titration.

Experiment 1

An experiment was set up as shown in Figure 1.  In Buret A is placed 15.0 ml of 0.2M H2SO4solution.  In Buret B is placed 50.0 ml of a potassium hydroxide (KOH) solution of unknown concentration.  The sulfuric acid is allowed to run into the Erlenmeyer flask and to the flask three drops of phenolphthalein are added.  The base is added drop by drop until the phenolphthalein turns a very faint pink color.  This is considered the end point of the titration.  The experiment is repeated three more times using other concentrations of potassium hydroxide (KOH).  The results of this experiment are summarized in Table 1.


Experiment 2


A second titration was done with a setup similar to that in Figure 1.  In this case, an iodine solution is placed in Buret A and various fruit juices are placed in Buret B.  Once the fruit juice was placed in the flask, several drops of a starch solution were added.  This solution would turn a blue-black color once the endpoint of the titration was reached.  The chemical reaction is as follows:

Ascorbic Acid + I2 → 2I- + dehydroascorbic acid

The results of this experiment are summarized on Table 2.

Question 1: One of the students doing Experiment 2 hypothesized that orange juice has the most Vitamin C of all the juices tested. Assuming that using more juice indicates the presence of more Vitamin C, is this hypothesis supported from the experiment?

A  No, since orange juice had the least Vitamin C and apple juice the most.

B  No, since orange juice had the least Vitamin C and cranberry juice the most.

C  Yes, since orange juice had the most Vitamin C and apple juice the least.

D  Yes, since orange juice had the most Vitamin C and grape juice the least.

Since the total volume used is the difference between the starting and ending volumes, the orange juice actually has the least Vitamin C as 50.0 – 43.8 = 6.2. According to these results, the apple juice has the most Vitamin C. The answer is A.

Weaken hypotheses questions can also appear in Data Interpretation and Research Summaries passages. Make sure to always examine the point of view of the student/scientist/author. Ask yourself if the data supports their conclusions, or not.

To find out what ACT skills you should work on next, check out your Skill Data on your Grockit profile. Grockit’s profile percentages adjust automatically with each question you answer, so the more questions you attempt, the more accurate your feedback on Grockit will be!

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ACT Science – 3 Tips to Get Better Scores

By posted December 6, 2011

The ACT Science Test is a lot easier than you think (after all, it’s basically an open book test)! Even if your knowledge of Science is limited, you can still get better scores through discipline and hard work. On Test Day, the ACT Science Test will always be the fourth test you’ll take. It will have 7 passages and you’ll have 35 minutes to complete them.

Find out other great ACT science strategies here!

  1. Practice your pacing! Don’t wait until two weeks before your test to get started. You will only have about 5 minutes per passage, so you may want to start by only doing 5 passages, allotting 7 min per passage. Once you can confidently do 5 passages with reasonable accuracy, work your way up to 6 and then 7. If you have a limited time to study and your accuracy significantly drops after 5 passages, just stick to 5 on Test Day. Better to do 5 really well and guess on 7 than to do all 7 sloppily.
  2. Always refer back to the passage. You won’t be able to memorize the information presented in the passages; it’s too overwhelming. Read the passages to understand the gist and the data that is presented, but also move back to the passage to locate the information you need to answer. Memory alone will not suffice, and you may find it helpful to jot down a few short notes on each passage. Drawing arrows and circling important info is also a great idea
  3. Adopt a strategy for each of the 3 formats. ACT Science Test passages come in three forms: Data Representation, Conflicting Viewpoints, and Research Summaries. You will need to modify your approach slightly for each one. Data Representation focuses mostly on charts, graphs, and tables, so you will need to practice identifying trends and understanding the layout of variables. Conflicting Viewpoints typically has no diagrams and is more like the paired passages you might remember if you took the SAT. Research Summaries describes one or more experiments. You will need to understand the Purpose, Method, and Results for each experiment, and know what the similarities and differences were between them. Don’t treat these 3 formats all the same – they are each quite unique!

Set a timer the next time your work on an ACT Science practice test, and see if you can stick to these checkpoints. This is the ideal timing for the actual exam:

:00 … Set the clock and begin!

:05….Finish gridding in the answers for Passage 1

:10….Finish gridding in the answers for Passage 2

:15….Finish gridding in the answers for Passage 3

:20….Finish gridding in the answers for Passage 4

:25….Finish gridding in the answers for Passage 5

:30….Finish gridding in the answers for Passage 6

:35….Finish gridding in the answers for Passage 7 (make sure you can do this before time is called!)

Ready to practice on some ACT Science passages? Join a game in the Grockit ACT lobby to work with other ACT students. You will start to see the three question-types, Data Representation, Conflicting Viewpoints, and Research Summaries. Practice identifying them with other students and share strategy tips!

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Recognizing Patterns on the ACT Science Test

By posted November 28, 2011

To get a great score on the ACT Science Test, you will need to understand the trends in presented data and be able to predict patterns for these trends as they apply to new situations. On ACT Test Day, pattern questions usually ask about the following: minimum or maximum levels, points of change, or direct/inverse variation.

Test your ACT science skills with this practice question today!

The minimum level is the smallest data point for a given entry. The maximum level is the largest data point for a given entry. Point of change occurs when preceding data has a different relationship to the remaining data. Direct variation means that two items are directly proportional: when one increases, the other increases. Inverse variation means that two items are indirectly proportional: when one increases, the other decreases. Sometimes you will be given a graph and asked to extrapolate, or to extend the graph beyond the values on the axes to find an x-value or a y-value that is out of the given range.

Let’s look at an example ACT example Pattern question from Grockit’s database:

Experiment 2 is repeated at a temperature of 45°C. Assuming that the results from both experiments continue to hold true, what is the most likely solubility (in g solute/100 g water) of Ca(NO3)2 at 800 torr?

  1. A. 25
  2. B. 30
  3. C. 35
  4. D. 40

The answer is D. Overall, since the solubility of all solids in Experiment 1 increases with increasing temperature, the logical pattern is that the solubility of Ca(NO3)2 would increase as its temperature increases. Initially, Experiment 2 was run at 25°C. Running it at 45°C should increase Na2HSO4’s solubility from the level of 35 g/100 g H2O. Pressure had no real effect on the solubility of any of the solids in Experiment 2.  Let’s look at a second example:

Table 1. Relative abundances of the elements in the Solar System

Element          Atomic #      Abundance (%)

H                      1                91.03

He                    2                  7.24

C                      6                  0.41

N                      7                  0.11

O                      8                  0.79

Ne                   10                 0.10

Mg                   12                0.05

Si                     14                0.05

ALL OTHER ELEMENTS >14     < 0.05

According to Table 1, as the atomic number increases from 8 to 9 to 10, the abundances:

A            Decrease, then increase

B            Increase, then decrease

C            Decrease only

D            Increase only

Note that the last line of the table indicates that the abundance of element 9 must be less than 0.05%. The abundance therefore decreases from 0.79% at element 8 to <0.05% at element 9, then increases again to 0.10% at element 10. The answer is A.

Sometimes the pattern will be more visual than numerical:

In Study 1, if the electrical activity of the resting volunteer had been measured for an additional 1 second, the voltages would have varied between approximately:

A            -5 and +5 microvolts

B            -25 and +25 microvolts

C            -50 and +50 microvolts

D            -100 and +100 microvolts

From 0 to 1 second, we can see the range was always between +25 and -25. There is no reason to assume that there would be any change if we were to continue this experiment for an additional second. The answer to this pattern question is B.

Need more help? Grockit’s ACT Tutors conduct private lessons via Skype to help you build your ACT strategy, customize your study plan, and to help answer he toughest ACT practice questions. Find out more on the Tutoring tab in the Grockit lobby, or go ahead and join a Group Game to practice with other ACT Students!

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