Q1. What is a scientific hypothesis?

Background

Topic: Scientific Method

This question tests your understanding of the definition and characteristics of a scientific hypothesis in the context of scientific inquiry.

Key Terms:

• Hypothesis: A proposed explanation for an observation, which can be tested through experimentation.

Step-by-Step Guidance

1. Recall that a hypothesis is an initial, testable statement or prediction about a scientific phenomenon.

2. Consider whether a hypothesis is meant to be permanent or subject to change as new evidence is gathered.

3. Think about whether a hypothesis is usually complex or simple, and whether it is considered absolute or tentative.

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Q2. Which of the following is NOT true for a scientific law?

Background

Topic: Scientific Laws vs. Theories

This question asks you to distinguish between what a scientific law is and what it is not, especially compared to theories and hypotheses.

Key Terms:

• Scientific Law: A statement that summarizes a pattern found in nature, often expressed mathematically.

• Scientific Theory: An explanation of why or how a phenomenon occurs, based on evidence.

Step-by-Step Guidance

1. Review the definitions of scientific law and scientific theory.

2. Identify which statements describe what a law does (summarizes data, universality, mathematical form).

3. Determine which statement incorrectly describes a law, possibly confusing it with a theory.

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Q3. In an experiment testing a new drug for cancer, which variable is easiest to control?

Background

Topic: Experimental Design and Variables

This question tests your understanding of independent, dependent, and controlled variables in scientific experiments.

Key Terms:

• Controlled Variable: A variable that is kept constant to ensure a fair test.

• Independent Variable: The variable that is changed or manipulated by the experimenter.

Step-by-Step Guidance

1. List the variables mentioned: amount of drug, patient's diet, air pollution exposure, exposure to other people.

2. Consider which variable can be most precisely measured and regulated in a laboratory or clinical setting.

3. Think about which variables are influenced by external factors and which are under direct control of the experimenter.

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Q4. What would be the weight on Mars of a person who weighs 150 pounds on Earth, given that gravity on Mars is one-third that of Earth?

Background

Topic: Gravity and Weight

This question tests your ability to apply proportional reasoning to calculate weight under different gravitational conditions.

Key Terms and Formula:

• Weight: The force exerted by gravity on an object, calculated as mass times gravitational acceleration.

• Proportionality: If gravity changes, weight changes in direct proportion.

Step-by-Step Guidance

1. Identify the person's weight on Earth: 150 lb.

2. Note that gravity on Mars is one-third that of Earth.

3. Set up the proportional relationship: $\text{Weight on Mars} = \text{Weight on Earth} \times \frac{1}{3}$

4. Multiply 150 lb by $\frac{1}{3}$ to find the weight on Mars.

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Q5. Which of the following is a physical change?

Background

Topic: Physical vs. Chemical Changes

This question tests your ability to distinguish between physical and chemical changes in matter.

Key Terms:

• Physical Change: A change in the state or appearance of matter without altering its composition.

• Chemical Change: A change that results in the formation of new substances.

Step-by-Step Guidance

1. Review each option and determine if the process involves a change in chemical composition or just a change in state/form.

2. Recall that melting, boiling, freezing, and dissolving (without reaction) are physical changes.

3. Identify which option describes a process where the substance remains the same at the molecular level.

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Q6. What are the characteristics of a gas?

Background

Topic: States of Matter

This question tests your understanding of the properties of solids, liquids, and gases.

Key Terms:

• Gas: A state of matter with no definite shape and no definite volume.

Step-by-Step Guidance

1. Recall the properties of solids (definite shape and volume), liquids (definite volume, indefinite shape), and gases.

2. Identify which option correctly describes a gas as having both indefinite shape and indefinite volume.

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Q7. How should vinegar be classified: pure substance, element, compound, or mixture?

Background

Topic: Classification of Matter

This question tests your ability to classify substances based on their composition.

Key Terms:

• Mixture: A combination of two or more substances that are not chemically bonded.

• Compound: A substance composed of two or more elements chemically combined in a fixed ratio.

Step-by-Step Guidance

1. Note that vinegar contains about 5% acetic acid and 95% water.

2. Determine if these components are chemically bonded or simply mixed together.

3. Recall that a mixture can have variable composition, while a compound has a fixed composition.

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Q8. How should refined white table sugar be classified?

Background

Topic: Classification of Matter

This question tests your understanding of the difference between elements, compounds, and mixtures.

Key Terms:

• Compound: A substance with a fixed composition and distinct chemical properties, made of two or more elements chemically bonded.

Step-by-Step Guidance

1. Recognize that table sugar always has the same composition of carbon, hydrogen, and oxygen, regardless of its source.

2. Recall that compounds have a fixed ratio of elements and consistent properties.

3. Decide whether sugar is an element, compound, or mixture based on this information.

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Q9. What do you call a substance that cannot be broken down by chemical means into simpler substances?

Background

Topic: Elements and Compounds

This question tests your understanding of the definition of an element.

Key Terms:

• Element: A pure substance that cannot be broken down into simpler substances by chemical means.

Step-by-Step Guidance

1. Recall the definitions of element, compound, and mixture.

2. Identify which term fits the description of a substance that cannot be decomposed further by chemical reactions.

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Q10. Which of the following represents a compound?

Background

Topic: Elements vs. Compounds

This question tests your ability to recognize chemical formulas that represent compounds.

Key Terms:

• Compound: A substance formed when two or more elements are chemically bonded together.

• Chemical Formula: A notation that shows the elements in a compound and the ratio of atoms.

Step-by-Step Guidance

1. Review the chemical symbols and formulas given: Co, Mn, CO2, Na.

2. Recall that compounds have formulas with more than one type of element.

3. Identify which formula represents a compound (contains more than one element symbol).

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