Practice Test- Experimental
Design
.
Experimental Design
1. Shakita wants to know if the pH of an open can of soda changes over time. To
test this, she designs an experiment that will involve the following steps.
1. Open a can of soda and measure the pH.
2. Allow the open soda can to rest undisturbed on a level countertop at room
temperature.
3. Measure the pH of the open soda can every day at the same time for ten
consecutive days.
What is the dependent variable in Shakita's experiment?
A. the pH of the soda
B. the type of soda
C. the temperature of the room
D. the number of days
Scientific Investigations
2. Major scientific theories include the cell theory, the big bang theory, and the
theory of plate tectonics. How are scientific theories formed?
A. through a single scientific discovery in which a scientist learns something new
B. through the formation of several related hypotheses
C. through extensive testing and the accumulation of several lines of evidence
D. through meetings between scientists in which they discuss several possible answers
to a scientific question
Experimental Design
3. In a controlled scientific experiment,
A. all variables are kept constant.
B. one or more variables are kept constant.
C. no variables are kept constant.
D. only one variable can be kept constant.
Scientific Investigations
4. Nancy needs to do a scientific investigation for her class. She is interested in
pottery, plants, and basketball. Which of the following questions would be
suitable for use in a scientific investigation?
A. How many needles grow on the giant redwoods in California?
B. What length of time is best to use for the firing of pottery to make it strong?
C. What color of carnation flowers do people find most attractive?
D. What is the most number of points ever scored in a professional basketball game?
Experimental Design
5. Carl knows that water moves through different kinds of soil at different rates.
How easily water moves through a soil is known as permeability. Carl decides to
compare the permeabilities of different soil types.
To do this, Carl takes five identical flower pots with holes in the bottom and fills
each one with different soil:





rocky, gravely dirt from the side of the road
potting soil from the store
clay soil from a nearby creek
sand from a store
dirt from his own backyard
Carl pours one liter of water into each pot and measures how much water flows
out of the bottom in one minute.
Which of the following variables should be kept constant during this experiment?
A. the permeability of the soil in each pot
B. the amount of water that goes into each pot
C. the amount of water that comes out of each pot
D. the kind of soil in each pot
Scientific Investigations
6. George is interested in spiders. He wants to study why spiders spin webs, so he
comes up with the following question: Do spiderwebs help spiders catch prey?
George's question is
A. not a valid scientific question because it asks about an opinion.
B. not a valid scientific question because it is not about science.
C. not a valid scientific question because it is not testable.
D. a valid scientific question because it is testable.
Experimental Design
7. Why is it important that a scientist keep accurate records of an experiment he
conducts?
A. in order to keep an accurate record of how many hours he spent in the lab
B. in order to receive a patent for any new product that he invents
C. in order to back up the conclusions he publishes as a result of the experiment
D. in order to reminisce over all his experiments after he retires
Scientific Investigations
8. A hypothesis...
A. is an optional step in a scientific investigation.
B. is the final step in a scientific investigation.
C. is not a strategy used in a scientific investigation.
D. is a necessary step in a scientific investigation.
Experimental Design
9. Walter learned in science class that different substances release heat at different
rates. He decides to test this.
At home, Walter turns the oven to 200°F. He places three casserole dishes in it:
one is made of metal, one is made of glass, and one is made of ceramic. He
leaves them in the oven for an hour. He then removes them from the oven,
places a single ice cube on each one, and times how long it takes the ice cube to
melt.
In this experiment, what is the independent variable?
A. the temperature of each pan
B. the material each pan is made of
C. the volume of each ice cube
D. the amount of time it takes for the ice to melt
Scientific Investigations
10. Derek lives in a hot, humid climate. He has two rose bushes in pots in his yard.
The rose bushes grow quickly and bloom with large, red roses. Derek moves to a
cold, dry climate at the same altitude and notices that his rose bushes stop
growing and do not have large blooms. He hypothesizes that the rose bushes are
not receiving enough water because he is now in a dry climate. He waters them
more often, but they do not improve.
Which of the following scientific questions should he ask next to find out what is
wrong with his roses?
A. Do rose bushes grow better in high or low altitudes?
B. Which rose bush has larger, more colorful blooms?
C. Does temperature affect the growth of the rose bushes?
D. How much do rose bushes cost in his new area?
Experimental Design
11. David is doing an investigation about factors that affect plant growth, so he
plants two young elm trees near each other in his garden. He gives the first elm
tree a gallon of water every week, and he gives the second elm tree fertilizer
once a month.
He plans on measuring the trees' heights and trunk girths every week for the
next year. How can David best improve his investigation?
A. place both trees in a greenhouse instead of his garden
B. use cedar trees instead of elm trees for the investigation
C. test only one independent variable at a time
D. do not measure the trees growth at all until a full year has passed
Scientific Investigations
12. A wildlife researcher wants to know how a species of fox behaves in its natural
habitat. The researcher should
A. observe the foxes in a laboratory.
B. perform an experiment on the foxes.
C. observe the foxes in their environment.
D. make a model of the foxes and their habitat.
Experimental Design
13. Emilio's teacher told his class that a controlled experiment's results are valid only
if one factor in the experiment is changed and all the other factors remain
constant. Why is this statement true?
A. Changing several different factors in an experiment takes too much time.
B. When only one factor is changed, you don't need to use a control.
C. Changing several different factors in an experiment takes too many controls.
D. When only one factor is changed, you can be more certain that it caused the results.
Scientific Investigations
14. Alexis was interested in the way mirrors reflect. The living room of Alexis' house
had one big window in the front, and a very large mirror on the back wall. Alexis
hypothesized that the room would heat up faster in the morning with the mirror
on the wall than it would if the mirror were covered with a sheet that was the
same color as the walls.
What will make Alexis' hypothesis valuable?
A. It will be valuable only if it is proved correct.
B. Any testable hypothesis is valuable.
C. It will be valuable only if it is proved incorrect.
D. It cannot be valuable because the investigation is in her house and not in the science
lab.
Experimental Design
15. Albert hypothesizes that a certain fungus causes black spot disease in roses.
Which of the following experimental designs would support or reject his
hypothesis?
A.
I.
Pot ten different species of flower plants, including at least one rose bush.
II.
III.
IV.
Isolate the flowers from each other.
Introduce the fungus into the soil of nine of the flowers.
Observe which, if any, flowers develop black spot disease.
B.
I.
II.
III.
IV.
Plant a flower garden.
Water the garden deeply.
Introduce the fungus into the soil of the flower garden.
Observe which, if any, plants develop black spot disease.
C.
I.
II.
III.
IV.
Pot ten rose bushes of the same breed.
Isolate the rose bushes from each other.
Introduce the fungus into the soil of all the rose bushes.
Observe which, if any, rose bushes develop black spot disease.
D.
I.
II.
III.
IV.
Pot ten rose bushes of the same breed.
Isolate the rose bushes from each other.
Introduce the fungus into the soil of nine of the rose bushes.
Observe which, if any, rose bushes develop black spot disease.
Scientific Investigations
16. Sara was walking through a forest in Hawaii. One thing that made an impression
on her was the distinct absence of bird sounds. As she continued walking through
the forest, Sara wondered why she did not hear or see any birds.
The scenario above is an example of how
A. a prediction can lead to a scientific experiment.
B. a scientific question can lead to a prediction.
C. a scientific question can lead to an observation.
D. an observation can lead to a scientific question.
Experimental Design
17. Aisha wonders whether wind or water causes the most erosion. She set up an
experiment in which she used a watering can to pour water down a pile of dirt.
She then used a fan to blow wind on a second pile of dirt that is the exact same
shape and size as the first pile of dirt. Aisha then measured how the height of the
dirt piles changed. She also drew pictures of how their shape changed. In this
experiment, what was the dependent variable?
A. the time the dirt piles were eroded away
B. the agent of erosion applied to the dirt piles
C. the height and shape of the dirt piles
D. the tools used to measure the dirt piles
Scientific Investigations
18. Students used to be taught that all the planets, stars, and the Sun moved around
the Earth. Scientists used observations they had made to chart out the paths
each planet must follow. The paths were very complicated. For example, the path
Mars took around the Earth is shown below:
Image from Astronomia Nova by Johannes Kepler, 1609
Using this model, scientists could predict fairly well where the planets would be
and how they would move at any point in the near future.
Today, students are taught that all the planets move around the Sun and that
the Earth spins on its axis once every 24 hours. Which of the following played the
largest part in changing what students are taught?
A. The world leaders changed their minds about what students should be taught.
B. A scientist came up with a theory that the planets move around the Sun.
C. The planets used to move around the Earth, but now they move around the Sun.
D. Enough data was gathered to show how the planets move.
Experimental Design
19. Julia wants to find out which color fabric will heat up the fastest when put under
a direct light.
So, she places pieces of red, white, and green fabrics outside in the sunlight.
Then, she places pieces of black, yellow, and blue fabric inside under a bright
lamp. Finally, she measures the temperature of all the fabric samples every 5
minutes.
Will Julia's results be valid?
A. Yes, all scientific investigations are valid.
B. No, she should only test one color of fabric at a time.
C. No, she has more than one independent variable.
D. Yes, she is conducting a controlled experiment.
Scientific Investigations
20. Sara wanted to do a scientific investigation that involved people and their sleep.
She hypothesized that all people feel happier if they take a one-hour afternoon
nap each day. Is her hypothesis valuable?
A. Yes; it will finally prove that everyone should have an afternoon nap time.
B. No; feelings are not testable.
C. No; hypotheses must not involve humans.
D. Yes; it will lead to new information on the results of napping.
Experimental Design
21. Jordan wants to conduct an experiment to see if plant food makes a difference in
how well plants grow. He gets 10 pots and plants a different type of seed in
each. He gives plant food to half of the plants and does not give plant food to the
rest. He records the amount of plant food given to the plants. But, he decides not
to write down the types of seeds he planted.
Will someone else be able to repeat the experiment and find reliable results?
A. No, because Jordan would need to use all vegetable seeds for the experiment to be
reliable.
B. Yes, because the type of seed is not important. As long as some of the plants are
receiving plant food and some are not, the experiment will give the same results.
C. No, because Jordan should have used the same type of seeds in each pot, and should
have recorded the type of seeds.
D. No, the results would not be reliable since not all of the plants were given plant food.
Scientific Investigations
22. Scientific experiments often produce new scientific knowledge.
What usually happens if a scientific experiment generates new knowledge that
doesn't agree with an existing theory?
A. The new knowledge is ignored in favor of the old theory.
B. Scientists choose whichever side seems to have the most followers.
C. The new knowledge is used to reevaluate the theory.
D. Science is abandoned as a way to generate knowledge.
Experimental Design
23. Nick hypothesizes that wax has a higher melting point than chocolate. How can
Nick test his hypothesis?
A. Measure the volume and weight of samples of wax and chocolate and calculate their
densities.
B. Use Mohs Hardness Scale to test how easily wax and chocolate can be scratched.
C. Heat samples of wax and chocolate and use a stopwatch to time how long it takes
until they start to melt.
D. Heat equal masses of wax and chocolate and measure their temperatures when they
start to melt.
Scientific Investigations
24. Scientific inquiry attempts to search out, describe, explain, and predict things
that happen in nature. Which of the following best describes how progress is
made in scientific inquiry?
A. by asking questions and collecting, analyzing, and interpreting different people's
opinions
B. by asking questions and collecting, analyzing, and interpreting data to answer them
C. by asking questions and researching the answers in papers, books, and on the
internet
D. by researching the history of science and learning about scientific progress in the past
Experimental Design
25. Michelle learns in science class that simple machines such as an inclined plane
can change the amount of force needed to lift heavy objects. She decides to test
this with an experiment.
Michelle chooses a 10 kg weight. She sets up a ramp made of smooth metal that
makes an angle θ with the floor. She attaches a spring scale to the weight and
the top of the ramp in order to hold the weight in place. She records the force
from the spring scale, then changes θ and records it again. She repeats this
several times.
In this experiment, what is the dependent variable?
A. the mass of the weight
B. the amount of force on the spring scale
C. the material the ramp is made of
D. the angle θ between the ramp and the ground
Scientific Investigations
26. Astronomers have observed that the universe is expanding and is accelerating in
all directions. Using this evidence, astronomers have hypothesized that a huge
explosion called the big bang created the universe. Which of the following
correctly describes the big bang?
A. none of these
B. opinion
C. theory
D. fact
Experimental Design
27. Selma hypothesizes that the mass of a sample of water will not change if it is
frozen. She conducts an experiment to test her hypothesis. Her experimental
steps are as follows:
1. Fill a beaker with 500 mL of water.
2.
3. Place the beaker in the freezer.
4. After the water freezes, place the beaker on the balance and
its mass.
measure
Which of the following steps is missing from Selma's experiment?
A. Run the water through a filter to make sure there are no impurities in it.
B. Set a timer for 2 hours.
C. Use a thermometer to measure the water's temperature.
D. Place the beaker on the balance and measure its mass.
Scientific Investigations
28. Katy has to do a science project that involves making a model. Which of the
following questions would she answer with a model?
A. How fast can different plant species grow?
B. Which type of bug can move the fastest?
C. What type of tree is the prettiest?
D. How does a volcano's lava flow affect the plants and objects in its path?
Experimental Design
29. Jenny dissolves as much salt as she can in 100 mL of room-temperature water.
She learned in class that less salt will dissolve in cold water than in hot water.
Jenny adds some ice to the salt water and observes what happens.
What effect will adding the ice to the solution have on the amount of salt that
can be dissolved into it?
A. It will allow more salt to be added to the solution because it adds water to the
solution.
B. It will force some of the salt to leave the solution because it will decrease the
temperature.
C. The effect is unpredictable because the ice changes two variables at the same time.
D. The ice will have no net effect on the amount of salt that can be dissolved in the
solution.
Scientific Investigations
30. A scientist is observing elephants in Asia. He notices that a specific species of
moth lands on the faces of the elephants. On closer observation, he sees that the
moths irritate the eyes of the elephants and then drink the tears that emerge.
What scientific question could the scientist ask to explain this?
A. What nutrients that moths need are in elephant tears?
B. Do other species of moths also drink elephant tears?
C. How can the moths be kept off the elephants' faces?
D. all of these
Experimental Design
31. Omar wants to determine if the mass of a model rocket affects how long the
rocket is able to stay up in the air. To do this, he constructs three identical
rockets and then fills two of the rockets with varying amounts of sand to add
mass. He then launches the rockets one at a time and times how long they are
able to stay airborne.
What is the independent variable in Omar's experiment?
A. the force with which each rocket is launched
B. the materials out of which the rockets were made
C. the masses of the model rockets
D. the time the rockets remain airborne
Scientific Investigations
32. What is the difference between a theory and an opinion?
A. A theory is a scientific fact, while an opinion is not.
B. An opinion is supported by scientific evidence, while a theory is not.
C. An opinion is a scientific fact, while a theory is not.
D. A theory is supported by scientific evidence, while an opinion is not.
Experimental Design
33. Cathy conducts a scientific investigation. How can she make sure her results are
valid?
A. write a report about her results
B. repeat the investigation several times
C. use metric measuring units during her investigation
D. confirm that her results match her hypothesis
Scientific Investigations
34. Henry is interested in studying the different techniques perching birds use to
build their nests.
What type of investigation would best help Henry learn more about this topic?
A. perform a controlled experiment
B. build a model of a nest
C. discover a previously unknown perching bird species
D. make observations in nature
Experimental Design
35. Which of the following should be done when designing an experiment for a
controlled scientific investigation?
A. plan the variables
B. list the needed materials
C. list the procedures
D. all of these
Scientific Investigations
36. A good question to use for a scientific investigation should be testable, and it
should be connected to science concepts.
Casey wants to do a scientific investigation about light. Which of the following
questions would be best to use to guide his scientific investigation?
A. Which type of light bulb is easiest to catch?
B. What color of light is the prettiest?
C. Which type of light bulb burns the longest?
D. Which type of light bulb is preferred by moms?
Experimental Design
37. Raul wants to study how pot size affects the growth of plants. To do this, he
intends to purchase three different pots of varying diameter. Then, he will fill
each pot with the same amount of soil and plant different kinds of flowers in each
pot. Finally, he will place the pots side by side in a sunny location and water each
pot daily with the same amount of water.
Will Raul's experimental set-up produce valid results?
A. Yes; Raul set up his experiment correctly so the results will be valid.
B. No; Raul doesn't have a testable hypothesis so the experiment is pointless.
C. Yes; Raul has a testable hypothesis so the experiment is valid.
D. No; Raul changes more than one variable so the results will be invalid.
Scientific Investigations
38. Addison has two dogs that are sisters. One of the dogs has white fur and the
other dog has black fur.
What scientific question could Addison ask based on this observation?
A. How is fur color determined in dogs?
B. Which of the dogs is the most friendly?
C. How fast do the dogs run?
D. Which color of fur is the prettiest?
Experimental Design
39. The factors that are kept the same throughout an experiment are called the
_______.
A. constants
B. variables
C. data
D. samples
Scientific Investigations
40. Jill hypothesizes that individual volcanoes produce igneous rocks with a certain
chemical signature. She further hypothesizes that scientists could use an igneous
rock's chemical signature to determine where the rock came from.
What type of investigation should Jill perform to test her hypothesis?
A. collect and test rock specimens
B. model the formation of an igneous rock
C. observe and describe a volcanic eruption
D. perform a controlled experiment on a volcano
Experimental Design
41. The observed results of an experiment that occur from changes in the
independent variable are known as _______.
A. dependent variables
B. constants
C. controlled variables
D. trials
Scientific Investigations
42. Juanita's next door neighbor has a theory that the best time to wash your car is
late in the afternoon on Sunday. Is this a scientific theory?
A. Yes, the car will stay clean for more of the week.
B. No, it is better to wash cars on Saturday.
C. Yes, the neighbor might be a scientist.
D. No, it is an opinion and is not testable.
Experimental Design
43. Beth wanted to find out whether or not salt affects how quickly ice melts. She
used an ice cube tray to make 10 ice cubes of the same shape and size. Then,
she placed the ice cubes on the same windowsill. She sprinkled each ice cube
with one teaspoon of salt, and timed how long it took for the cubes to melt. She
recorded all of the data.
If someone else read the data, would he or she be able to make an accurate
conclusion about the effect of salt on ice?
A. No, because the data does not show how quickly the ice would have melted without
the salt.
B. Yes, because Beth used only one independent variable and everything else was the
same.
C. Yes, because using 10 ice cubes gives enough trials for the results to be accurate.
D. No, because Beth should have used a different amount of salt on each of the ice
cubes.
Scientific Investigations
44. A scientific question
A. produces repeatable investigations.
B. involves things that are measurable.
C. is testable.
D. all of these
Experimental Design
45. Juan wants to see how air expands when it is heated. He is able to use any of the
following supplies - a balloon, a heat lamp, a spring scale, and a meter stick.
Which is the best procedure to follow for the experiment?
A. Inflate the balloon, heat the balloon using the heat lamp, and measure the weight of
the balloon with the spring scale.
B. Measure the weight of the deflated balloon, inflate the balloon, heat the balloon with
the heat lamp, then measure the inflated balloon's width.
C. Use the spring scale to measure the weight of the balloon before and after it is blown
up.
D. Inflate the balloon, measure the width of the balloon, heat the balloon using the heat
lamp, and then measure the width again.
Scientific Investigations
46. In ancient times, many people believed in a geocentric model of the solar
system, where the Earth was the center of the system. During the 16th and 17th
centuries, men such as Copernicus, Kepler, and Galilei theorized or found
evidence that the Sun was actually the center of the solar system. However,
despite convincing evidence, this idea was not accepted until some time later.
Why was this idea not initially accepted?
A. The Sun is not large enough to be at the center of the solar system.
B. There was no evidence published supporting their ideas.
C. It is difficult to change a commonly held belief.
D. After a theory has been around for one hundred years, it cannot be changed.
Experimental Design
47. Which of the following statements describes all the variables in an experiment?
A. All variables are changed from one part of the experiment to another.
B. All variables are measured to provide data for the experimental results.
C. All variables affect the results of the experiment.
D. All variables are kept the same from one part of the experiment to another.
Scientific Investigations
48. Belinda is interested in dog behavior. She has formed a hypothesis that dogs are
able to hear higher-frequency sounds than humans. What should Belinda do
next?
A. Write a paper describing how she formed her hypothesis.
B. Form another hypothesis about dogs.
C. Design an experiment to test her hypothesis.
D. Make observations of other mammals.
Experimental Design
49. Julian designs an experiment to see how well different liquids lubricate wooden
surfaces. He sets up a number of identical wooden ramps and prepares to slide
identical wooden blocks down them. He will time how long it takes each block to
reach the end of the ramp. He covers one ramp with water, the second with
motor oil, and the third with corn syrup.
What can Julian use as a control group for the experiment?
A. a block that drops straight down instead of sliding down a ramp
B. a ramp with no liquid on it
C. a ramp with no friction on its surface
D. a second set of ramps covered with water, oil, and syrup respectively
Scientific Investigations
50. Which of the following is an example of a testable scientific hypothesis?
A. Roses grow faster in the Sun than in the shade.
B. Why do plants grow better in the Sun than in the shade?
C. Gorillas are happier in the wild than they are in the zoo.
D. Peacocks have prettier tail feathers than pigeons do.
Experimental Design
51. In science class, Harry and his classmates are performing a controlled scientific
investigation. The teacher has already picked a topic and testable question for
the class to study and has provided background research on the topic.
Before performing the investigation, the students must first
A. communicate the results of the investigation with the teacher.
B. record data from the investigation in graphs and charts.
C. form a hypothesis to predict the outcome of the investigation.
D. analyze the data that results from the investigation.
Scientific Investigations
52. Maria hypothesizes that the amount of light in an environment affects the growth
of algae living in that environment.
Which of the following is the best type of investigation for Maria to perform in
order to test her hypothesis?
A. collect and observe different specimens of algae
B. build a computer model of algae growth
C. conduct a controlled experiment
D. observe algae in nature
Experimental Design
53. A student would like to determine how heating a liquid changes its volume. The
student hypothesizes that the liquid will increase in volume. The following list
shows the steps taken by the student in order to test the hypothesis.
I.
II.
III.
IV.
V.
Select the liquid to test.
Place the liquid in a sealed container.
Use a Bunsen burner to heat the liquid by 10°C.
Measure the volume of the liquid.
Record the results.
What is wrong with how the student conducted the investigation?
A. The volume of the liquid should be measured before it is heated.
B. The hypothesis was not valid because it is impossible for liquids to change in volume.
C. The student should have increased the temperature of the liquid by more than 10C.
D. The length of time it took for the liquid to be heated should be measured.
Scientific Investigations
54. Which of the following is a testable hypothesis?
A. Hurricanes look larger in images taken by an orbiting satellite than in video footage
taken by weather reporters standing on Earth's surface.
B. The growth rate of an E. coli bacterial colony will increase as temperature increases
from 10 °C to 50 °C.
C. High levels of salt in soil will probably affect plant growth by either making the plants
grow better or causing the plants to die.
D. Is there a proportional relationship between the number of pimples a person gets and
the amount of chocolate he/she eats?
Experimental Design
55. Ned is designing an experiment to test which hand sanitizer kills the most E. coli
bacteria. In order for Ned's results to be valid, what must he do?
A. test the hand sanitizers on bacterial colonies that are kept in the exact same
environmental conditions, such as temperature and light level
B. test the first brand of hand sanitizer on E. coli bacteria, then test the second brand of
hand sanitizer on a sterilized Petri dish
C. test each hand sanitizer on different days and at different times of the day
D. test the hand sanitizers first on E. coli bacteria and then on other bacterial species
Scientific Investigations
56. Carla likes to garden. One side of Carla's garden is shaded by nearby trees and
does not get much light. The other side gets plenty of light. Carla notices that
the plants in her garden grow at different rates.
Carla decides to perform an investigation based on her observations. What
should be the next steps in her investigation?
A. Change her observations, then draw a conclusion.
B. Make a hypothesis about her observations, then write a report about the observation
and hypothesis.
C. Draw a conclusion, and then collect data.
D. Form a question about her observations, then make a hypothesis to answer that
question.
Experimental Design
57. Olivia researched insects that destroy farmers crops. Based on this information,
she discovered a way to keep the insects away from the plants, without adding
any harmful chemicals to the crops. She recorded her conclusion, but did not
write down any of the resources she used to learn about the insects. She also did
not record information about any of the trials that did not work. Does she need
to include this information?
A. Yes, because the information could be helpful to other scientists conducting similar
research.
B. No, because she is the one who made the discovery. Listing the resources she used
would give credit to other people.
C. She should include the sources of the articles she read, but the trials that did not
work are not important.
D. No, because Olivia put a lot of time and effort into finding this information. Other
people should have to do the same.
Scientific Investigations
58. Sometimes scientists gather information that contradicts accepted theories or
explanations. If the new information is replicated many times, the accepted
theory that it contradicts will often be updated or modified to reflect the new
information.
Based on this, it can be determined that scientific knowledge is durable in part
because
A. it is open to change as new information is learned.
B. new information on accepted theories is never discovered.
C. scientists ignore information that contradicts accepted theories.
D. experiments are never performed more than once.
Experimental Design
59. Javier has found a beetle during a field study. He suspects that it might be a new
species of beetle that no one has ever documented before. He takes the beetle
back to his lab and examines it under a microscope.
What does Javier need to do so that he can accurately compare his beetle to
known species of beetle?
A. Javier must collect some of the beetle's tissue so it can be cloned.
B. Javier must compare the beetle's foot speed to that of an ant.
C. Javier must carefully record and describe the beetle's response to laser light.
D. Javier must carefully record and describe all of the characteristics of his beetle.
Scientific Investigations
60. Mimi has three pet dogs. Their bodies are all about the same size, but one dog
has long legs, one dog has medium-length legs, and one dog has short legs.
Mimi notices that all three dogs run at different speeds.
Mimi asks herself 'Why do my dogs run at different speeds?' Which of the
following hypotheses should Mimi test to answer her question?
A. A dog with long legs will run faster than a dog with short legs.
B. The more attractive a dog is, the faster it will run.
C. What size of dog runs the fastest?
D. How does the age of a dog affect the speed at which it runs?
Answers
1. A
2. C
3. B
4. B
5. B
6. D
7. C
8. D
9. B
10. C
11. C
12. C
13. D
14. B
15. D
IV.
16. D
17. C
18. B
19. C
20. B
21. C
22. C
23. D
24. B
25. B
26. C
27. D
28. D
29. C
30. A
31. C
32. D
33. B
34. D
35. D
36. C
37. D
38. A
39. A
40. A
41. A
42. D
43. A
44. D
45. D
46. C
47. C
48. C
49. B
50. A
51. C
52. C
53. A
54. B
55. A
56. D
57. A
58. A
59. D
60. A
Explanations
1. Variables are the parts in an experiment which change.
Independent variables (the variables that are manipulated by the experimenter)
determine the values of the dependent variables (the variables that respond to the
independent variables).
In Shakita's experiment, the pH of the soda is the dependent variable. Time, or the
number of days, is the independent variable.
2. In science, a theory is a unifying explanation for a broad range of hypotheses and
observations that have been supported by testing. The gathering of evidence and the
peer review of that evidence are hallmarks of scientific thought.
3. In a controlled scientific experiment, a scientist alters one variable, called the
independent variable. The scientist then studies the effects of this alteration on another
variable, called the dependent variable. Any other variables involved the
experiment are kept constant.
4. To be used for a scientific investigation, a question has to be testable and it needs to
have a connection to scientific concepts. The best length of time to fire pottery to make
it strong is both testable and scientific. The other options can either be determined by
simply looking up the answer (rather than performing an investigation) or are not
testable because they would be based on opinion/emotion rather than fact.
5. In an experiment, anything that is not the independent variable or the dependent
variable should be kept the same for every trial. In this experiment, the following
factors should remain the same:




the amount of water that goes into each pot
the type of pot that is used
the size and number of holes in each pot
the amount of time waited for the water to run through the soil
These factors are known as constants.
6. A scientific question must be testable and can be answered using data and facts
obtained from research, observations, or experiments. It cannot be used to ask about
opinions or emotions. "Do spiderwebs help spiders catch prey?" is a valid, testable
scientific question.
7. Scientists keep accurate records of their experiments for many reasons. The most
important reason, though, is to maintain their credibility if any of their findings
are ever questioned by other scientists.
8. Scientific investigations involve collecting evidence (experimentation), reasoning,
devising hypotheses, and formulating explanations to make sense of collected evidence.
9. In this experiment, the independent variable is the material each pan is made of.
The dependent variable is how long it takes each ice cube to melt. All other variables
should be kept constant, including the amount of ice put in each pan, the temperature
of each pan, and the temperature of each ice cube.
10. The first climate that Derek lived in was hot and humid. He moved to an area that was
cold and dry. The rose bushes grew well in the hot, humid climate but started to die in
the cold, dry climate. Derek first asked if the difference in moisture was causing the
rose bushes to die. He watered them more, but there was no change.
Since his new climate is cold instead of hot, the next question Derek should ask is:
"Does temperature affect the growth of the rose bushes?"
11. In a controlled experiment, only one factor (the independent variable) should vary.
David currently has two independent variables in his experiment (a watering schedule
for one tree and a fertilizer treatment for the other tree). David can improve his
investigation by testing only one independent variable at a time.
12. A wildlife researcher needs to observe the foxes in their environment to learn how
the foxes behave in the wild.
A fox will act differently if an experiment is set up in a laboratory, so the observations
must be made in the wild to make sure they are correct.
13. There are several ways to make sure the results of an investigation are valid. First, you
and others can try to repeat the experiment. In addition, if it is a controlled experiment,
you can make sure you have a control, only one independent variable, at least one
dependent variable, and constants.
It is especially important to use only one independent variable because when only one
factor is changed, you can be more certain that it caused the results. If you
change multiple factors, you won't know which one was responsible for the change.
14. Every testable hypothesis is valuable because it can lead to new information.
15. Only one variable should be changed at a time in a controlled scientific experiment. In
this experiment, only rose bushes should be used. Different species of flower plants
should not be used.
Controlled scientific experiments should also have a control group. The control group is
left untreated, so the changed groups can be compared to it. In this experiment, the
rose bush that was not treated with fungus is the control group.
16. Sometimes, an observation can be the absence of something expected. In this example,
Sara observed the lack of bird sounds or sightings. This observation led her to question
why there was no evidence of birds in the forest.
The scenario in this question is an example of how an observation can lead to a
scientific question.
17. A dependent variable is a variable in an experiment that is passively observed. The
dependent variable is affected by the independent variable.
18. When people still believed that the planets moved around the Earth, they already had
enough data to know how the planets move. What they needed was a theory that fit
the data better than their current theory. Johannes Kepler was the first person to
present a theory that fit the data better than the theory that the planets moved around
the Earth. He said that the planets move around the Sun in elliptical orbits. Eventually,
his theory changed what most people believe and, therefore, what students are taught.
Note: Although Kepler was not the first scientist to propose that planets move around
the Sun, he was the first to come up with elliptical orbits. A model in which planets
orbited the Sun in perfect circles was not able to predict the planets' motions as
accurately as the Earth-centered model of that time.
19. There are several ways to make sure the results of an investigation are valid. First, you
and others can try to repeat the experiment. In addition, if it is a controlled experiment,
you can make sure you have a control, only one independent variable, at least one
dependent variable, and constants.
In this case, Julia has multiple independent variables (the color of the fabric and the
light source), so the results will not be valid.
20. Sara's hypothesis is not testable; this makes it invalid as a scientific hypothesis and
not valuable.
21. For an experiment to be reliable, there can be only one independent variable. In this
scenario, there were two. The first was whether or not the plants were given plant food.
The second was the type of seed. For the test to be reliable, he should have used the
same kind of seed for each plant. Then, some should have been given plant food while
the rest were not. If someone else were to repeat the experiment, they would need to
know what types of seeds were used. And, they would need to have only one
independent variable in order to get reliable results.
22. New scientific knowledge is often used to reevaluate existing theories.
Some scientific theories are very good at describing the way the world works. But even
very good theories sometimes come up against new information that does not agree
with them. When this happens, the theory needs to be reevaluated.
The result is usually that the theory is refined and made more accurate, taking into
account the new information.
23. To test his hypothesis, Nick should heat equal masses of wax and chocolate and
measure their temperatures when they start to melt.
24. Scientific inquiry progresses by constantly asking questions and collecting,
analyzing, and interpreting data in order to answer them. Researching something in
books, articles, and on the internet is a good way to learn, but it can only teach what
someone else has already figured out. To make new discoveries, new questions must be
asked and answered with objective data.
25. The dependent variable in an experiment is the one that is affected by changing the
independent variable. In this experiment, the independent variable is the angle θ
between the ramp and the ground. The dependent variable is the amount of force on
the spring scale that is required to hold the weight in place on the ramp.
26. Since the idea of the big bang is supported by scientific evidence, it is called a theory.
It is not called a fact because it has not been proven.
27. In order to see if the mass of the water changed, Selma first needs to find out what the
mass of the liquid water is in order to compare it to the mass of the frozen water.
28. Models are used in science experiments, where the actual problem is not easily found or
created. Thus, a small model of the event or object to study is made and the
experiment is performed on the model.
A good example of an experiment that would need a model is to answer how a
volcano's lava flow affects the plants and objects in its path.
29. The ice lowers the temperature of the solution, which decreases the amount of salt that
can be dissolved in it. However, as the ice melts, it also adds water to the solution,
which increases the amount of salt that can be dissolved in it. The net results of adding
ice to the solution will be unpredictable because the ice changes two variables at
the same time.
30. Investigating whether another species of moth also drinks tears might be interesting,
but it would not directly explain why this species of moth does.
To explain why this species of moth drinks tears, the scientist could ask: "What
nutrients that moths need are in elephant tears?"
The scientist could experiment with moth repellent or other ways to keep the moths
away, but that would not answer his original question.
31. Variables are the parts in an experiment which change. Independent variables
determine the values of the dependent variables.
In Omar's experiment, the independent variable is the mass of the model rocket.
This variable is controlled by Omar and ultimately determines the values of the
dependent variable (the amount of time that the rockets remain airborne).
32. A theory is a statement meant to explain something in nature. Although a theory has
not been proven as fact, it is supported by scientific evidence. An opinion is not
supported by scientific evidence.
33. There are several ways to make sure the results of an investigation are valid. First, you
and others can try to repeat the experiment. In addition, if it is a controlled
experiment, you can make sure you have a control, only one independent variable, at
least one dependent variable, and constants.
34. Different scientific questions and hypotheses require different types of scientific
investigations. Some questions can be answered through controlled experiments. Other
questions can be answered through collecting specimens, building models, and/or
making observations.
A question regarding animal behavior can be best answered by making observations
in nature.
35. When designing an experiment for a controlled scientific investigation, the designer
should:





plan the variables (manipulated and responding)
plan for controlled variables
list the needed materials
list the procedures
plan for recording, organizing and analyzing data from the experiment
36. The prettiness of a light bulb cannot be directly measured. The question "Which type of
light bulb is preferred by moms?" is not related to scientific concepts about light or light
bulbs. A question about catching light bulbs does not make much sense since light bulbs
cannot move on their own. The best scientific question is, "Which type of light bulb
burns the longest?"
37. Raul's experimental set-up will not produce valid results because he intends to change
more than one variable.
One variable that Raul will change is the pot size. According to the description, however,
Raul will also change one other variable—the type of flower that is planted. Even though
Raul plans on using flowers only, he should use the same type of flower in each pot, not
different types.
Valid results are only produced when only one variable is changed at a time.
38. Scientific questions can be asked about observations. Addison observed that her two
dogs have different colors of fur. To figure out why the two dogs have different colors of
fur, she could ask: "How is fur color determined in dogs?"
Science cannot be used to determine which of the dogs is the most friendly or which
color of fur is the prettiest. The observation of fur color does not reveal anything about
running speed.
39. Variables are factors that can be changed during an experiment.
The constants of an experiment are the factors that are kept the same throughout
different trials of the experiment.
40. Different scientific questions and hypotheses require different types of scientific
investigations. Some questions can be answered through controlled experiments. Other
questions can be answered through collecting specimens, building models, and/or
making observations.
Jill's hypothesis could best be tested by collecting and testing rock specimens from
multiple volcanoes in various locations.
41. The observed results of an experiment that occur from changes in the independent
variable are known as dependent variables. For example, if a student wants to
determine how the amount of water given to a plant effects how much the plant grows,
the growth of the plant is the observed result that occurs because of changes to the
amount of water the plant receives.
42. Many times people will use the word theory when they are really just stating an opinion
or speculating. These opinions and speculations cannot be proven right or wrong.
A scientific theory, on the other hand, is a well-supported explanation of nature. It is
based on scientific knowledge and has been tested through experimentation.
In this case, the best time to wash a car is really a matter of opinion and not a
testable explanation of nature.
43. Scientific experiments must have a control group to be used for comparison. The control
group is exposed to the same conditions, without being exposed to the independent
variable. In this case, Beth should have placed several identical ice cubes in the
windowsill without any salt. This would show how quickly the ice would melt without
salt. Someone reading the data could then make a conclusion based on the results. The
melting times of the two groups of ice cubes could be compared to determine whether
or not salt affected how fast ice melts.
44. All of these are true. Scientific questions are testable and generally do not involve
matters of opinion, personal values, or beliefs. Scientific questions are tested through
scientific investigations that are repeatable and that involve things that are measurable.
45. When designing an experiment, always keep in mind the question that needs to be
answered.
In Juan's case, he wants to see how air expands when heated. Therefore, he will need
to inflate the balloon, measure the width of the balloon, heat the balloon using
the heat lamp, and then measure the width again.
46. The idea that the Sun is at the center of the solar system was not originally accepted,
despite convincing evidence, because it is difficult to change a commonly held
belief. Science changes constantly, as new inventions and methods are created to
achieve more reliable data. It is important that people understand that science changes
and that even commonly believed theories can change as new information is presented.
47. Variables are any factors that affect the results of the experiment. Some variables
are changed throughout the experiment, some are kept the same, and others are
measured.
48. Scientists form hypotheses about subjects they are interested in studying. A hypothesis
helps a scientist design a scientific experiment. Experiments are designed to test
whether a hypothesis is correct. Belinda's next step is to design an experiment to
test her hypothesis.
49. A good control for this experiment would be to slide each block down its ramp with no
liquid on it first, then add the liquid and slide the block down it again.
50. A scientific hypothesis must be testable and it must be written as a statement, not as a
question. "Roses grow faster in the Sun than in the shade" is a testable, scientific
hypothesis.
A hypothesis cannot involve opinion, such as whether a peacock or a pigeon has prettier
tail feathers. The happiness of an animal cannot be tested scientifically.
51. Harry's teacher has already performed the first two steps of a controlled scientific
investigation. Once the topic is identified and researched, Harry and his classmates
should form a hypothesis to predict the outcome of the investigation.
After forming a hypothesis, Harry and his classmates should design an experiment to
test the hypothesis. They should then perform the experiment, analyze the results of
the experiment, and communicate the results to the class.
52. Different scientific questions and hypotheses require different types of scientific
investigations. Some questions, such as questions involving how one factor affects an
organism or event, can be answered through controlled experiments. Other questions
can be answered through collecting specimens, building models, and/or making
observations.
53. During an experiment to test how a variable changes a substance, it is important to first
observe and record the characteristics of the substance before the variable is
introduced. In this case, the variable is heat energy. The student must first record
the liquids volume, before attempting to change the volume by introducing
heat energy.
54. There are many types of scientific investigations. Some investigations are designed to
gather information by observing. For instance, a scientist may observe and record how
many birds of a certain type visit a feeding station. Some investigations involve
surveying people to gain insight into their needs and opinions. Some investigations
require making models to manipulate factors that cannot or should not be manipulated
in a natural setting. Finally, some investigations, called controlled laboratory
experiments, involve manipulating one variable or factor and measuring or observing
the response of another variable or factor.
Before beginning any of these types of investigations, a scientist must form a testable
hypothesis. The hypothesis should be stated clearly, in sentence (not question) form. It
should not use vague or general language. Rather, it should present a very specific
prediction about what will be observed or discovered during the investigation.
55. There are several ways to make sure the results of an investigation are valid. First, you
and others can try to repeat the experiment. In addition, if it is a controlled experiment,
you can make sure you have a control, only one independent variable, at least one
dependent variable, and constants.
For Ned's results to be valid, he needs to test the hand sanitizers on bacterial
colonies that are kept in the exact same environmental conditions, such as
temperature and light level.
56. After Carla has made observations, she should form a question about her
observations, then make a hypothesis to answer that question. Then, she can
perform the rest of the investigation and write a report about her results and
conclusions.
57. It is important to include all information, including resources and unsuccessful trials.
This information could be beneficial to other scientists. They could use this information
to further benefit the farmers and the consumers who buy the food from the crops.
58. Scientific knowledge is open to change as new information is learned.
Perhaps the biggest reason why scientific information has proved to be so useful and
lasting is that it is constantly subject to change. Theories and explanations only last as
long as they're able to accurately predict what will happen in experiments. So when
significant data is gathered that contradicts a theory, that theory must be modified to
agree with the data. Sometimes this means the theory needs to be abandoned
completely.
59. Javier must carefully record and describe all of the characteristics of his beetle.
Javier might have found a new species of beetle. But he will only be able to figure this
out if he has carefully recorded all of the details of the beetle. So Javier must closely
observe it, and take careful notes. After he has done this, he can compare his
description to that of known species.
60. Mimi knows that her dogs have legs of different lengths. After seeing that her dogs run
at different speeds, Mimi might make the following hypothesis: "A dog with long legs
will run faster than a dog with short legs."
Observations often lead to questions. To answer these questions, scientists develop
hypotheses. Finally, the hypotheses are tested in experiments, and conclusions are
drawn.
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