Read know english 7 potx

At the beginning of the experiment the concentration of the reactant was at a maximum.. a commercial pesticide is used but ample food is provided.. bay leaf, an alleged natural moth repe

performed on scatter plots Here is an example The scatter plot shows the concentration of a reactant (con-sumed in a chemical reaction) as a function of time

Notice that data were not taken at the beginning of the experiment (zero seconds) and beyond 500 sec-onds If you assume that the thick line will maintain its shape in both directions, you can solve this problem

At the beginning of the experiment the concentration of the reactant was at a maximum Therefore, it had

to be higher than 0.15 mol/liter If you extend the thick data line to the y-axis (the gridline corresponding to

zero seconds), while maintaining the shape of the curve, you can estimate the initial concentration of the reac-tant was about 0.18 mol/liter How about the concentration at 600 seconds? At 300 seconds, the concentra-tion of the reactant seems to have leveled of at 0.05 mol/liter It stays the same at 400 seconds, at 450 seconds, and 500 seconds Wouldn’t you bet that the concentration will remain 0.05 mol/l at 600 seconds?

D RAWING C ONCLUSIONS

To draw a conclusion, we take all available facts into account, and make a decision or statement based on all these facts put together

Question: Did he do it?

Facts: The accused had a motive, no alibi, and the unfortunate luck of being seen by the nosy

neighbor

Conclusion: The accused is guilty.

In the case of science, in very much the same way, we need to pull all the information available together, sum it up, and make a judgment or prediction

Example 1

Question: If you were looking for a metal whose heat transfer properties didn’t vary much

over a wide range of temperature, which metal from the list in the preceding example would you use?

Concentration of a Reactant

as a Function of Time

0.20 0.15

0.10

0.05

0.00

Time [s]

Facts: Thermal conductivity of platinum hardly changes with temperature The variation of

other metals with temperature is greater

Conclusion: Platinum.

Example 2

Facts: The average woman ovulates on the 14th day of her cycle Release of the ovum from

the ovary is hormonally stimulated

Question: Which hormone is most responsible for ovulation?

More facts (after looking at the scatter plot): The concentration of LH, rapidly increases

from the day 11 to day 13 of the cycle, immediately preceding the ovulation event, and then

it rapidly drops

Conclusion: The concentration of LH increases to stimulate ovulation Once ovulation

occurs, the concentration of LH decreases, since more stimulation is not required One ovum

is enough

Summary

In this lesson you learned about different types of graphical representation, including tables, scatter plots, bar graphs, pie graphs, and diagrams You now have an idea of which graphical representation is most useful for

a given scenario, that for example, pie graphs are used to show the portion of a whole taken up by a subset

of that whole You know how to locate the essential elements of graphical representation (axes, labels, titles, and legends), and how to find and interpret the information you are asked about You can look for trends (such as increasing and decreasing), compare different sets of data, interpolate and extrapolate, as well as draw conclusions and make predictions However, having these skills up your sleeve is only a start, you will need

a great deal of practice (See page 283 for ACT Science Reasoning Test practice questions.)

R ESEARCH S UMMARIES

Research Summary passages require you to read one or more related experiments and to analyze them to cor-rectly answer the questions that follow Each experiment has more or less the same structure There is a pur-pose—to prove or disprove some hypothesis, to determine what material is best for an application, what conditions are favorable, or to find what might be causing problems with an experiment

This lesson will help you develop skills you will need to:

■ read and understand descriptions of one or more related experiments

■ draw conclusions and make predictions based on the research results

■ How many experiments are discussed in the passage?

■ What is the purpose of the experiment(s)?

■ What are the variables in the experiment?

■ Which variables are controlled by the scientist, and how?

■ Which variables are measured or observed, and how?

■ Were any calculations performed?

■ Is there an experimental control? If so, what is it?

■ If more than one experiment is presented, how is each experiment similar/different?

Take a look at the following example:

Example 1

A student working in an optics lab needs a filter that will transmit (pass through) more than 90%

of green light, while absorbing (getting rid of) 95% of near-infrared light She finds six filters in the lab, but they are not labeled, so she is not sure whether any of them will work

She has a 632 nm green laser, a 1,064 nm near-infrared laser, and a suitable detector She decides to measure the intensity of each laser with the detector, and then to mount different fil-ters in the path of each of the lasers, recording the transmitted intensity with the detector The data she obtains are tabulated below:

Initial Transmitted

Initial Transmitted

Have you read the passage and looked at the data carefully? Answer the relevant questions listed at the beginning of the lesson

1 How many experiments are discussed in the passage?

Just one.

2 What is the purpose of the experiment(s)?

To find a filter that satisfies specified criteria.

3 What are the variables in the experiment?

There are six different filters and two different lasers (of different intensity and wavelength—green and near-IR) Amount of different type of laser light transmitted by a particular filter is also a variable.

4 Which variables are controlled by the scientist and how?

The wavelength is controlled, using two different lasers Different filters are aligned in the path of the lasers.

5 Which variables are measured or observed and how?

The initial intensity of each laser is measured using a detector Intensity of light (for each of the lasers) transmitted through each filter is measured using the detector as well.

As you can see, quickly answering for yourself these few simple questions enables you to determine the functions of different parts of the experiment, and to stay focused on what is important Here is another example:

Example 2

Meal moths are one of the most common pantry pests They often nest in flour, cereal, pasta, seeds, and dried fruits they find in kitchen and pantry cabinets A scientist decided to compare the effec-tiveness of different methods of ridding the household from this pest The scientist wanted to know how the total number of adult moths would vary over time when

1 all food is removed.

2 a commercial pesticide is used but ample food is provided.

3 bay leaf, an alleged natural moth repellant is used but ample food is provided.

4 all food is removed and a commercial pesticide is used.

5 all food is removed and bay leaf is used.

6 ample food is provided and no pesticide or repellant is used.

For each of the six experimental settings, the scientist designed a closed container (10 cubic feet) with ample air supply, and conditions such as temperature and light adjusted to resemble an aver-age kitchen He then placed 10 adult moths (both male and female) in each container, along with the appropriate amount of food and bay leaf He sprayed pesticide in the containers of Group 2 and 4 once a day The data he collected over 7 days are tabulated below

Food

taken Bay

away leaf Pesticide Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7

Now that we have read the passage, underlined or marked key information, made notes in the margins

of the text, and analyzed the data in the table, answer the relevant questions from the beginning of the lesson:

1 How many experiments are discussed in the passage?

Only one.

2 What is the purpose of the experiment(s)?

To compare the efficiency of different methods of meal moth extermination.

3 What are the variables in the experiment?

The variables are food, pesticide, bay leaf, time, and the number of moths in a container.

4 Which variables are controlled by the scientist and how?

The scientist controls the contents of each container—food, pesticide, bay leaf, and the initial number of moths.

5 Which variables are measured or observed and how?

The number of moths in each container is observed over the course of seven days.

6 Were any calculations performed?

No calculations were performed.

7 Is there an experimental control? If so, what is it?

The experimental control is the group of moths (6) in the container where ample food is available, and no pesticide or bay leaf is present It corresponds to the situation where nothing is being done to eliminate the moth population.

You may still not understand all the details of this experiment, but the questions above probably helped you organize the information that was presented to you, and you can now proceed to the more challenging task of interpreting the experiments and the experimental results

Analysis

When reading Research Summary passages you will have to think about the following questions: What do the results show? What do they mean? How does the measured or observed variable depend on the controlled