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AEPA Chemistry NT306 study materials
AEPA Chemistry NT306 study resources

AEPA Chemistry NT306 practice questions

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Question 1Nature of Science

A student measures the mass of a sample three times and obtains 10.2 g, 10.3 g, and 10.2 g, but the accepted value is 11.0 g. Which statement best describes these measurements?

  1. They are both accurate and precise.
  2. They are neither accurate nor precise.
  3. They are precise but not accurate. Correct answer.
  4. They are accurate but not precise.

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to how close a measurement is to the true value. The three trials cluster tightly together (high precision) but sit about 0.7 g below the accepted value (low accuracy).

Question 2Nature of Science

In an experiment, the variable that the researcher deliberately changes is called the:

  1. dependent variable
  2. extraneous variable
  3. independent variable Correct answer.
  4. controlled variable

Explanation

The independent variable is the factor the experimenter manipulates to observe its effect. The dependent variable is the measured response, and controlled variables are held constant.

Question 3Nature of Science

Which of the following is the best example of a scientific hypothesis?

  1. Water boils at 100 degrees Celsius at sea level.
  2. Salt water is more interesting than fresh water.
  3. If salt is added to water, then the boiling point will increase. Correct answer.
  4. A thermometer is used to measure temperature.

Explanation

A hypothesis is a testable, falsifiable prediction often stated as an if-then relationship between variables. It proposes an outcome that can be checked by experiment.

Question 4Nature of Science

A scientist repeats an experiment several times to confirm the results. This practice primarily serves to:

  1. eliminate the need for a control group
  2. guarantee the hypothesis is true
  3. improve the reliability of the findings Correct answer.
  4. increase the sample size

Explanation

Replication checks whether results are consistent and reduces the influence of random error, which improves reliability. It does not by itself prove a hypothesis or remove the need for controls.

Question 5Nature of Science

Which of the following is a qualitative observation?

  1. The solution has a mass of 12 g.
  2. The solution is clear and blue. Correct answer.
  3. The solution's temperature is 25 degrees Celsius.
  4. The solution has a volume of 50 mL.

Explanation

Qualitative observations describe properties using the senses or non-numerical descriptions, such as color or clarity. Quantitative observations involve measurements with numbers and units.

Question 6Nature of Science

Which of the following best describes a scientific theory?

  1. An opinion held by most scientists
  2. A well-tested explanation supported by extensive evidence Correct answer.
  3. A guess made before any data are collected
  4. A single experiment's result

Explanation

In science, a theory is a broad, well-substantiated explanation of natural phenomena built from many lines of evidence. It is far stronger than a guess or a single result.

Question 7Nature of Science

A graph shows the relationship between temperature and the volume of a gas. The independent variable is plotted on which axis?

  1. The horizontal axis Correct answer.
  2. Either axis, at the researcher's choice
  3. Neither axis; it is shown in the legend
  4. The vertical axis

Explanation

By convention, the independent variable (the one manipulated) is placed on the horizontal x-axis, and the dependent variable is placed on the vertical y-axis.

Question 8Nature of Science

Which statement reflects an appropriate use of significant figures when reporting a measurement?

  1. Drop all digits after the decimal point.
  2. Report every digit the calculator displays.
  3. Always report exactly two digits.
  4. Round to the precision the instrument can reliably support. Correct answer.

Explanation

Significant figures communicate the precision of a measurement, so results should be reported only to the level the instrument can support. Reporting extra digits implies false precision.

Question 9Nature of Science

A researcher wants to test whether fertilizer affects plant growth. She gives one group of plants fertilizer and another group no fertilizer, keeping light, water, and soil identical. The group receiving no fertilizer is the:

  1. control group Correct answer.
  2. independent variable
  3. experimental group
  4. dependent variable

Explanation

The control group serves as a baseline for comparison because it does not receive the treatment being tested. Keeping other factors identical isolates the effect of the fertilizer.

Question 10Nature of Science

A student wants to determine how the concentration of acid affects the rate of a reaction. Which factor should be held constant?

  1. The time to completion
  2. The temperature Correct answer.
  3. The acid concentration
  4. The reaction rate

Explanation

In a controlled experiment, only the independent variable (acid concentration) is changed, and all other factors such as temperature must be held constant. The reaction rate and time are dependent outcomes.

Question 11Nature of Science

A scientist plots data and finds that as one variable increases, the other decreases in a consistent manner. This describes:

  1. a negative correlation Correct answer.
  2. a causal relationship
  3. no correlation
  4. a positive correlation

Explanation

When one variable rises while the other falls, the relationship is a negative (inverse) correlation. Correlation alone, however, does not establish causation.

Question 12Nature of Science

Which of the following is the most appropriate unit for expressing the density of a solid in SI-based terms?

  1. meters per second
  2. moles per liter
  3. grams per milliliter
  4. grams per cubic centimeter Correct answer.

Explanation

Density is mass per unit volume. For a solid, grams per cubic centimeter is a standard metric unit, consistent with mass divided by volume.

Question 13Nature of Science

A student claims that because two variables are correlated, one must cause the other. Which criticism of this claim is most valid?

  1. Correlation does not rule out confounding variables or coincidence. Correct answer.
  2. Correlation can only be shown with a control group.
  3. Correlation always proves causation.
  4. Correlation requires a single data point.

Explanation

A correlation shows that two variables move together but does not establish that one causes the other; confounding factors or chance may explain the pattern. Controlled experiments are needed to support causal claims.

Question 14Nature of Science

A measurement is reported as 0.00450 g. How many significant figures does this value have?

  1. Six
  2. Two
  3. Three Correct answer.
  4. Five

Explanation

Leading zeros are not significant, but the trailing zero after a nonzero digit following a decimal point is significant. Thus 4, 5, and the final 0 give three significant figures.

Question 15Nature of Science

In a valid experiment, which practice most helps reduce bias in assigning subjects to treatment groups?

  1. Using only volunteers from one group
  2. Assigning subjects based on the researcher's judgment
  3. Testing only the treatment group
  4. Random assignment of subjects to groups Correct answer.

Explanation

Random assignment distributes unknown or confounding traits evenly across groups, reducing bias and making groups comparable. Researcher judgment or nonrandom selection can systematically skew results.

Question 16Nature of Science

Which of the following best represents a peer-reviewed source for scientific information?

  1. A social media post shared many times
  2. An article in a scholarly journal evaluated by experts in the field Correct answer.
  3. A personal blog post about a home experiment
  4. A product advertisement on a company website

Explanation

Peer review means independent experts in the field evaluate the methods and conclusions before publication, which increases credibility. Blogs, advertisements, and social media posts generally lack this scrutiny.

Question 17Nature of Science

A student calculates a result of 3.456 g and must report it to the correct number of significant figures based on measurements of 2.0 g and 1.456 g. The result of the addition should be reported as:

  1. 3.46 g
  2. 3.5 g Correct answer.
  3. 3.456 g
  4. 3 g

Explanation

In addition and subtraction, the result is limited by the least precise decimal place among the addends. The value 2.0 is known only to the tenths place, so the sum must be rounded to the tenths place, giving 3.5 g.

Question 18Nature of Science

A graph of experimental data shows points that follow a clear upward trend but are scattered around the best-fit line. What does the scatter most likely indicate?

  1. Random measurement error is present. Correct answer.
  2. The independent variable was not controlled.
  3. The hypothesis is disproven.
  4. The data should be discarded.

Explanation

Scatter around a trend line typically reflects random measurement error or natural variation, not a failed hypothesis. The overall trend can still be meaningful despite the scatter.

Question 19Nature of Science

Which of the following statements about the relationship between science and technology is most accurate?

  1. Science and technology are completely unrelated.
  2. Science seeks understanding while technology applies knowledge to solve problems. Correct answer.
  3. Science is only concerned with building devices.
  4. Technology always precedes scientific discovery.

Explanation

Science aims to build knowledge and explanations about the natural world, while technology applies that knowledge to practical problems. The two influence each other but serve distinct purposes.

Question 20Nature of Science

A scientist develops a model to explain atomic structure. Which statement best describes the role of models in science?

  1. Models replace the need for experiments.
  2. Models are exact copies of reality.
  3. Models are simplified representations used to explain and predict. Correct answer.
  4. Models are permanent and never revised.

Explanation

Scientific models are simplified representations that help explain observations and make predictions. They are useful but approximate and are revised as new evidence emerges.

Question 21Nature of Science

A researcher measures the boiling point of a liquid five times: 78.1, 78.2, 78.1, 78.0, and 78.1 degrees Celsius. The accepted value is 78.1 degrees Celsius. Which conclusion is best supported?

  1. The measurements are accurate but imprecise.
  2. The measurements are both accurate and precise. Correct answer.
  3. The measurements are precise but inaccurate.
  4. The measurements show a systematic error.

Explanation

The trials cluster tightly around one another (high precision) and center on the accepted value (high accuracy). Both criteria are satisfied, so the data are accurate and precise.

Question 22Nature of Science

An experiment yields a result with a percent error of 2 percent and very low variability between trials. Which interpretation is most defensible?

  1. The result is precise and reasonably accurate. Correct answer.
  2. The result is precise but highly inaccurate.
  3. The result is neither accurate nor precise.
  4. The result is accurate but imprecise.

Explanation

Low variability among trials indicates high precision, and a small percent error indicates the result is close to the accepted value, so accuracy is good. Both qualities are present.

Question 23Nature of Science

A scientist wants to determine whether a new drug lowers blood pressure. She designs a study with a treatment group and a placebo group, and neither the participants nor the researchers know who receives which. This design is best described as:

  1. a case study
  2. a correlational survey
  3. a double-blind controlled experiment Correct answer.
  4. an observational study

Explanation

A double-blind controlled experiment uses a placebo comparison and conceals group assignment from both participants and researchers to reduce bias. This design supports causal inference about the drug's effect.

Question 24Nature of Science

Two students measure the same quantity. Student A's measurements are all close to each other but far from the accepted value; Student B's measurements are spread out but average to the accepted value. Which statement is most accurate?

  1. Student A has high accuracy but low precision; Student B has high precision but low accuracy.
  2. Student A has high precision but low accuracy; Student B has low precision but high accuracy on average. Correct answer.
  3. Student B's data are invalid because they are spread out.
  4. Both students have equally high accuracy and precision.

Explanation

Precision is about agreement among repeated trials, while accuracy is about closeness to the true value. Student A's tight cluster shows precision without accuracy, and Student B's spread values average to the true value, showing accuracy without precision.

Question 25Nature of Science

A result is statistically significant at the 0.05 level. Which interpretation is most appropriate?

  1. The experiment had a 5 percent error rate.
  2. The observed result would be unlikely if the null hypothesis were true. Correct answer.
  3. The result proves the alternative hypothesis.
  4. There is exactly a 5 percent chance the hypothesis is true.

Explanation

A significance level of 0.05 means that if the null hypothesis were true, a result at least as extreme as the observed one would occur about 5 percent of the time. It is a statement about the data under the null hypothesis, not a proof.

Question 26Nature of Science

Which of the following best describes the purpose of a control group in an experiment?

  1. To provide a baseline for comparison against the experimental treatment Correct answer.
  2. To ensure that all variables change simultaneously
  3. To increase the total number of subjects in the study
  4. To eliminate the need for repeated trials

Explanation

A control group is used as a standard of comparison. It does not receive the experimental treatment, so any effect observed in the treatment group can be attributed to the treatment rather than to other factors.

Question 27Nature of Science

A scientist measures the mass of a sample three times and obtains 2.45 g, 2.46 g, and 2.44 g. The true mass is 2.50 g. Which statement best describes the measurements?

  1. They are neither accurate nor precise.
  2. They are precise but not accurate. Correct answer.
  3. They are accurate but not precise.
  4. They are both accurate and precise.

Explanation

Precision refers to how close repeated measurements are to each other, while accuracy refers to how close they are to the true value. The measurements are close together (precise) but consistently lower than the true mass (not accurate).

Question 28Nature of Science

Which of the following is an example of a testable scientific hypothesis?

  1. There is intelligent life on other planets.
  2. The color blue is the most beautiful color.
  3. The universe is expanding at an accelerating rate.
  4. Plants grow taller when exposed to classical music. Correct answer.

Explanation

A testable hypothesis must be able to be supported or refuted by observation or experiment. The effect of music on plant growth can be tested with controlled experiments.

Question 29Nature of Science

In a scientific investigation, what is the primary role of repeating an experiment multiple times?

  1. To eliminate the need for a control group
  2. To reduce the effect of random errors and increase confidence in the results Correct answer.
  3. To increase the likelihood of obtaining the desired result
  4. To prove that the hypothesis is true

Explanation

Replication helps to identify and reduce the impact of random errors, leading to more reliable and trustworthy results. It also allows scientists to assess the consistency of the findings.

Question 30Nature of Science

A student wants to test how the angle of a ramp affects the speed of a toy car at the bottom. Which variable should be kept constant?

  1. The distance the car travels along the ramp
  2. The mass of the toy car Correct answer.
  3. The speed of the car at the bottom
  4. The angle of the ramp

Explanation

In a controlled experiment, all variables except the independent variable must be held constant. The mass of the car should remain the same so that any change in speed can be attributed to the angle of the ramp.

Question 31Nature of Science

Which of the following best describes a scientific law?

  1. A statement that describes a consistent natural phenomenon but does not explain why it occurs Correct answer.
  2. A well-substantiated explanation of some aspect of the natural world
  3. A guess based on limited observations
  4. A tentative explanation that can be tested by further investigation

Explanation

A scientific law describes a consistent relationship or pattern in nature, often expressed mathematically, but it does not provide an explanation for why the pattern exists. Explanations are provided by scientific theories.

Question 32Nature of Science

A scientist proposes a new model for the structure of an atom. Which of the following is the most important criterion for the model to be accepted by the scientific community?

  1. It must be consistent with existing experimental data and make testable predictions. Correct answer.
  2. It must be mathematically complex.
  3. It must be proposed by a well-known scientist.
  4. It must be simple and easy to understand.

Explanation

Scientific models are accepted based on their ability to explain existing observations and to make predictions that can be tested. Simplicity, authority, and complexity are not primary criteria.

Question 33Nature of Science

What is the main difference between a scientific theory and a scientific law?

  1. A theory can be changed, while a law is absolute and never revised.
  2. A theory is well-tested and widely accepted, while a law is a tentative idea.
  3. A theory is based on opinions, while a law is based on facts.
  4. A theory explains why something happens, while a law describes what happens. Correct answer.

Explanation

Scientific theories provide explanations for natural phenomena, while scientific laws describe consistent patterns or relationships. Both are well-supported by evidence and can be revised with new data.

Question 34Nature of Science

A student measures the volume of a liquid using a graduated cylinder with markings every 1 mL. The liquid level is between 43 mL and 44 mL. How should the student report the measurement?

  1. 43 mL
  2. 44 mL
  3. 43.5 mL Correct answer.
  4. 43.50 mL

Explanation

When using an analog scale, one should estimate one digit beyond the smallest marking. Since the markings are every 1 mL, the student can estimate to the nearest 0.1 mL, so 43.5 mL is appropriate.

Question 35Nature of Science

Which of the following best describes the role of peer review in the scientific process?

  1. It allows the general public to vote on which research should be published.
  2. It guarantees that the research is correct.
  3. It helps ensure that research meets standards of quality and significance before publication. Correct answer.
  4. It replaces the need for experimental evidence.

Explanation

Peer review is a process where experts in the field evaluate a manuscript for quality, validity, and significance. It helps maintain scientific standards but does not guarantee correctness.

Question 36Nature of Science

A scientist conducts an experiment and obtains results that contradict her hypothesis. What is the most appropriate next step?

  1. Report the results and consider revising the hypothesis based on the evidence. Correct answer.
  2. Ignore the results because they are likely due to error.
  3. Modify the hypothesis to fit the data without further testing.
  4. Discard the data and repeat the experiment until the hypothesis is supported.

Explanation

In science, contradictory data are valuable because they can lead to revised hypotheses and new insights. The appropriate response is to report the findings honestly and adjust the hypothesis accordingly.

Question 37Nature of Science

Which of the following is the best example of a scientific model?

  1. A physical replica of the solar system used to demonstrate planetary motions Correct answer.
  2. A hypothesis that has not yet been tested
  3. A law that describes the relationship between force and acceleration
  4. A collection of all experimental data from a study

Explanation

A scientific model is a representation of an object, system, or concept that is used to explain and predict phenomena. A physical replica of the solar system is a model because it represents the real system.

Question 38Nature of Science

A scientist wants to determine whether a new fertilizer increases crop yield. She divides a field into two plots: one receives the fertilizer, the other does not. Both plots receive the same amount of water and sunlight. At the end of the season, she measures the yield. Which of the following is the independent variable?

  1. The crop yield
  2. The type of fertilizer applied Correct answer.
  3. The amount of water and sunlight
  4. The size of the plots

Explanation

The independent variable is the factor that is deliberately changed by the researcher. Here, the presence or absence of fertilizer is the variable being manipulated.

Question 39Nature of Science

A student claims that a new study proves that a certain food causes cancer. Which statement best evaluates this claim?

  1. The claim is valid because the study was published.
  2. A single study can prove causation if it is well designed.
  3. Scientific studies can only show correlation; causation requires multiple lines of evidence. Correct answer.
  4. The claim is invalid because cancer has no known causes.

Explanation

A single study, even a well-designed one, rarely establishes causation on its own. Causation is typically established through a body of evidence from multiple studies and consideration of other criteria.

Question 40Nature of Science

Which of the following best describes the relationship between science and technology?

  1. Science and technology are the same thing.
  2. Technology drives scientific discovery, but science does not influence technology.
  3. Science and technology are independent fields with no overlap.
  4. Science seeks to understand the natural world, while technology applies scientific knowledge to solve practical problems. Correct answer.

Explanation

Science is the systematic study of the natural world, while technology is the application of scientific knowledge for practical purposes. They are interdependent and often advance together.

Question 41Matter and Its Properties

Which of the following is a chemical property of a substance?

  1. Its melting point
  2. Its solubility in water
  3. Its density at 20 °C
  4. Its tendency to react with oxygen Correct answer.

Explanation

A chemical property describes how a substance changes composition through a reaction, such as its reactivity with oxygen. Density, melting point, and solubility describe the substance without changing its identity.

Question 42Matter and Its Properties

A sample of pure water is found to contain 11.2 g of hydrogen and 88.8 g of oxygen. Which law is best illustrated by these fixed mass proportions?

  1. Ideal gas law
  2. Law of multiple proportions
  3. Law of conservation of mass
  4. Law of definite proportions Correct answer.

Explanation

The law of definite proportions states that a given compound always contains the same elements in the same mass ratio. Water's hydrogen-to-oxygen mass ratio is fixed regardless of sample source.

Question 43Matter and Its Properties

Which statement correctly distinguishes a homogeneous mixture from a heterogeneous mixture?

  1. A homogeneous mixture can be separated by filtration, while a heterogeneous mixture cannot.
  2. A homogeneous mixture has variable composition, while a heterogeneous mixture has fixed composition.
  3. A homogeneous mixture has a uniform composition throughout, while a heterogeneous mixture does not. Correct answer.
  4. A homogeneous mixture contains only one element, while a heterogeneous mixture contains compounds.

Explanation

A homogeneous mixture is uniform in composition at the molecular scale, such as salt water. A heterogeneous mixture has visibly or measurably non-uniform regions, such as sand and iron filings.

Question 44Matter and Its Properties

How many significant figures are in the measured value 0.004560 kg?

  1. 4 Correct answer.
  2. 7
  3. 3
  4. 6

Explanation

Leading zeros are not significant, but trailing zeros after a decimal point and nonzero digits are. The digits 4, 5, 6, and the trailing 0 are all significant, giving four.

Question 45Matter and Its Properties

Which subatomic particle determines the identity of an element?

  1. Electron
  2. Proton Correct answer.
  3. Neutron
  4. Photon

Explanation

The number of protons in the nucleus, the atomic number, uniquely identifies an element. Changing the proton count changes the element itself.

Question 46Matter and Its Properties

An atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number?

  1. 17
  2. 34
  3. 18
  4. 35 Correct answer.

Explanation

Mass number equals the sum of protons and neutrons: 17 + 18 = 35. Electrons are negligible in mass and are not included.

Question 47Matter and Its Properties

Which of the following represents a physical change?

  1. Iron rusting in moist air
  2. Baking soda reacting with vinegar
  3. Ice melting into liquid water Correct answer.
  4. Wood burning in a fireplace

Explanation

Melting changes only the physical state of water; the chemical identity H2O remains the same. The other options produce new substances with different compositions.

Question 48Matter and Its Properties

Which pair lists an element and a compound, respectively?

  1. Oxygen gas and carbon dioxide Correct answer.
  2. Salt water and sugar
  3. Brass and steel
  4. Air and water

Explanation

Oxygen gas (O2) is a pure element, and carbon dioxide (CO2) is a compound of two elements. The other pairs are mixtures or do not match the element-compound pattern.

Question 49Matter and Its Properties

Which group on the periodic table contains the alkali metals?

  1. Group 1 Correct answer.
  2. Group 2
  3. Group 17
  4. Group 18

Explanation

Group 1 elements, excluding hydrogen in most contexts, are the alkali metals such as lithium and sodium. Group 2 holds alkaline earth metals, Group 17 halogens, and Group 18 noble gases.

Question 50Matter and Its Properties

A substance has a mass of 24.6 g and a volume of 3.00 mL. What is its density, expressed to the correct number of significant figures?

  1. 0.122 g/mL
  2. 8.2 g/mL
  3. 8.200 g/mL
  4. 8.20 g/mL Correct answer.

Explanation

Density equals mass divided by volume: 24.6 ÷ 3.00 = 8.20 g/mL. The volume has three significant figures, so the answer is reported to three.