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Physics and Chemistry in

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NCVPS ACTScience

on 4 April 2014

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Transcript of Physics and Chemistry in

If you replace the spring in Trail 2 with another spring with a higher spring constant (k), then the spring will be harder to stretch, and have a lower discplacement (x)
You will get three separate data representation passages - and they are all very straightforward
Reading Data Representation Questions:
Read the Chart Questions
- these test your ability to locate and understand data right in the chart
Wrap Up
If left at rest, a spring will hang at its equilibrium position. If a mass (M) is attached to that spring, the spring will grow in length by a distance known as its displacement (x). A larger mass will create a larger displacement than a small mass.
Sample Physics Question
Physics and Chemistry in
ACT Data Representation

Examples, ideas, tips, and tricks...
Rather than trying to figure out what the definition of each variable is when reading, try to find what the question is asking in the data. For example, you don't need to know that Fe3+ is ferric iron, you just need to know the effect of its concentration at each depth.
Tips for Reading
Sample Chemistry Question
The following table represents the concentration of ions and dissolved gases in the sediment at the bottom of an ocean. A depth of 0 centimeters (cm) represents the top of the sediment. The concentrations are expressed in parts per million (ppm). The acidity of a solution is represented on a scale known as pH. A pH of 1 is very acidic, a pH of 7 is neutral, and a pH of 14 is very basic.
Take the Next Steps Question
Which of the following statements about displacement and the force on the spring is consistent with the data in Table 1?
A. The force on the spring increases as displacement increases.
B. The force on the spring decreases as displacement increases.
C. The force on the spring does not change as displacement increases.
D. The force on the spring increases then decreases as displacement increases.

Read the Chart Questions
Handle the Graphs Questions
According to the information provided in the introduction and Table 1, which of the following is the largest mass?
A. M1 B. M3 C. M5 D. M6
Use the Chart Questions
What would be the best method of determining how the spring constant affects displacement?
A. Reproduce Trials 1–6 but use only springs with spring constant k = 5.
B. Reproduce Trials 1–3.
C. Reproduce Trials 4–6.
D. Reproduce Trials 1–6 but change the masses in Trials 4–6 to M1, M2, and M3, respectively.
Take the Next Steps Questions
Read the Chart Questions
The graph below best represents the relationship between concentration and sediment depth for which of the following ions and dissolved gases?

F. Ferrous iron (Fe2+)
G. Oxygen (O2)
H. Carbon dioxide (CO2)
J. Sulfate (SO42-)
Handle the Graphs Questions
Use the Chart Questions
Try Another Using the Chart Question
Tips for Data (and 4 Types of Q's)
The force (F), in newtons (N), required to return the spring to its equilibrium position is the negative product of the displacement (x) and a spring constant (k), where the negative indicates the direction, not the value, of the force. The spring constant measures the elasticity of a spring: if a spring has a high k, the spring cannot be stretched easily; if a spring has a low k, it can be stretched more easily.
Various masses were attached to two springs with different spring constants, and the force was measured in each of these trials. The energy used (J) returning the spring to its equilibrium position, or Potential Energy (PE), was also measured.
Which of the following graphs best represents the change in potential energy with increasing displacement for Trials 1–3 ?
Each one starts with a written introduction which is a great start - but don't stress over it! Circle any terms that you may not understand, and try to get an idea of their meaning from the diagrams.
When you get to the chart (there may be one or two), be sure that you understand what is being measured
Use the Chart Questions
- uses information from the chart in order to figure out other information
Handle Graph Questions
- asks you to transform the data in the chart in to graph form
Next Step Questions
- gives you a stated goal and asks what can be done to test this next idea.
Recognize any trends (consistent increase or decrease) in the charts and highlight or note them
Look for correlations - do those trends relate to trends in other variables?
Understand the value of the variables - in a data chart, they are entries in the table. In a graph, the values are read off the scales at the bottom and sides of the graphs
The correct answer is...
A
If left at rest, a spring will hang at its equilibrium position. If a mass (M) is attached to that spring, the spring will grow in length by a distance known as its displacement (x). A larger mass will create a larger displacement than a small mass.
The questions refers you to the introduction and the table - so use those items. (shown)
These questions can help you focus on what information the chart is giving
The question is asking you to identify the relationship between two numbers - the displacement (x) and the force on the spring (F)
Note Trail 1-3 are a separate spring from Trail 4-6. Take this into account when answering
The introduction states "A larger mass will create a larger displacement than a small mass" which indicates that you should look for the amount of displacement to gauge the relative size of the masses. This leads you to M3 or M6 being the largest mass (they both have a displacement of 10m).
If you note the force on the spring (F) shown, you will then see that of the two (M3 or M6), M6 needs more force to stretch the spring. Since the only force on on spring is the hanging mass, you can assume that M6 has a larger mass.
The correct answer is...
D
If Trial 2 were repeated with a spring with k = 15, the displacement of the spring would be:
A. less than 5.
B. 5.
C. greater than 5.
D. indeterminable from the given information.
Try Another Use the Chart Question
The force (F), in newtons (N), required to return the spring to its equilibrium position is the negative product of the displacement (x) and a spring constant (k), where the negative indicates the direction, not the value, of the force. The spring constant measures the elasticity of a spring: if a spring has a high k, the spring cannot be stretched easily; if a spring has a low k, it can be stretched more easily.
This requires you to understand the sentence "if a spring has a high k, the spring cannot be stretched easily; if a spring has a low k, it can be stretched more easily."
Make your guess before moving on!
If you replace the spring in Trail 2 with another spring with a higher spring constant (k), then the spring will be harder to stretch, and have a lower discplacement (x)
The correct answer is...
A
You should know the basics of how to graph data and the difference between linear and exponential functions. These questions will test you being able to graph the data given.
Straight
horizontal
line - the variable on the y axis remains
constant
Straight
line trending
up
- the variable on the y axis is
increasing linearly
Straight
line trending
down
- the variable on the y axis is
decreasing linearly
Curved
line trending
up
- the variable on the y axis
increases exponentially
Curved
line trending
down
- the variable on the y axis
decreases

exponentially
Handle the Graphs Questions
Which of the following graphs best represents the change in potential energy with increasing displacement for Trials 1–3 ?
First, look at the relationship between displacement and potential energy in the chart. When displacement goes up, what does the PE do?
First look at the axes of the graphs. Each graph represents displacement on the x-axis (horizontal), while potential energy is represented on the y-axis (vertical). As you move right on the x-axis and up on the y-axis, numerical values increase.
Because Potential Energy goes UP, you can eliminate A & B
Answer C shows an exponential relationship and answer D shows a linear relationship.
The correct answer is...
C
Make sure you understand what the question is asking you to find...
This question is asking you to test springs with different constants, but three of the options call for using only one spring!
The correct answer is...
A
The keys are to get a general idea of what information the chart is trying to convey (trends) and less about knowing what every word means.
According to the information provided in the table, the concentration of which of the following ions and dissolved gases is constant for sediment depths of 10cm or more?
A. Sulfide (S2-)
B. Carbon dioxide (CO2)
C. Ferric iron (Fe3+)
D. Oxygen (O2)
If the trends indicated in the table were to continue, one would predict the pH of the sediments at a depth of 35 cm to be:
A. 1.5.
B. 3.5.
C. 4.5.
D. 6.0.
Underline the description of the chart in the accompanying paragraph. Make sure you understand what the chart is trying to show you!
Don't spend a large amount of time trying to understand the data - move on to the questions! Many times, the chart will make more sense once you see what the questions are asking for!
The question tells you to reference the table...
The question tells you to only look at depths of 10cm and below...
The question asks you which sediment is CONSTANT (which means it stays the same)
The correct answer is...
D
Once again look at your chart...
A certain type of bottom-dwelling microorganism thrives under the following environmental conditions: low concentrations of Fe2+, high concentrations of O2, and a neutral pH. Based on the table, at which of the following sediment depths would one most likely find this microorganism?
F. 0 cm
G. 5 cm
H. 10 cm
J. 15 cm
First you want to find low concentrations of Fe2+
Then you are looking for high levels of O2
Then you are looking for a "neutral" pH
MANY chemistry questions involve pH. You should know that a 7 is
neutral
, below a 7 is a
base
, and above a 7 is an
acid
.
The correct answer is...
F
Figure out the variables on your graph and what they correspond with on your chart.
As the sediment depth increases, what happens to the concentration?
The concentration goes from near 1, up to around 3, and down to about 1 again. (Note: we do not know the exact numbers from the graph, but can get close!)
If we look at our chart, we see one of the sediments does that same pattern!
The correct answer is...
H
A researcher wants to determine whether an unidentified sediment sample was drawn from a depth of 15 cm or 20 cm. Based on the information in the table, which of the following would NOT confirm the depth of the sample?
A. O2 concentration
B. Fe3+ concentration
C. S2- concentration
D. pH
The question tells you specifically to only look at depths of 15cm and 20cm
The question asks what would NOT confirm if it is 15cm or 20cm, so what are you looking for?
Look for which variable is the same at both depths!
The correct answer is...
A
While you want to get the general ideas of it, do not spend a lot of time trying to "figure out" the passage before moving on to the questions. Many questions only require working knowledge of the charts and graphs.
Brush up on some basic science terminology in classes you have taken in previous years, as it will help with your passage comprehension.
Because the question says that the "trends indicated in the table were to continue," this is a simple prediction problem. First, look at the two variables the question asks about.
The Depth (cm) goes up by 5cm each time
25
30
35
The pH goes down by 0.5 each time
4.5
4.0
3.5
The correct answer is...
B
Full transcript