Intro to Chemistry Exam 1 Review – Step-by-Step Study Guidance

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

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.
Tentative: Not certain or fixed; provisional.

Step-by-Step Guidance

Recall that a hypothesis is an initial explanation that can be tested by experiments or observations.
Consider whether a hypothesis is meant to be absolute, complex, simple, or tentative.
Think about the role of a hypothesis in the scientific method—does it serve as a final answer or as a starting point for investigation?

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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 in comparison to theories and hypotheses.

Key Terms:

Scientific Law: A statement based on repeated experimental observations that describes some aspect of the universe.
Summarize: To give a brief statement of the main points.
Explain: To make clear the cause or reason for something.

Step-by-Step Guidance

Review the difference between a law and a theory: laws describe what happens, theories explain why.
Look at each option and decide if it describes a law (summary, mathematical form, universality) or a theory (explanation).
Identify the statement that does not fit the definition of a scientific law.

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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 during an experiment.
Independent Variable: The variable that is changed or manipulated by the experimenter.
Dependent Variable: The variable being tested and measured.

Step-by-Step Guidance

Identify which variables are easiest to keep constant in a clinical setting (e.g., amount of drug, diet, environment).
Consider which variable can be measured and administered precisely by the experimenter.
Compare the options and select the one that is most directly under the experimenter's control.

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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 on different planets based on gravity differences.

Key Terms and Formula:

Weight: The force exerted by gravity on an object, calculated as mass × gravitational acceleration.
Proportionality: If gravity is one-third, weight will be one-third as well (assuming mass is constant).

Step-by-Step Guidance

Identify the person's weight on Earth (150 lb).
Recognize that Mars' gravity is one-third of Earth's.
Set up the proportional relationship: Weight on Mars = (1/3) × Weight on Earth.
Multiply 150 lb by 1/3 to find the weight on Mars, but stop before calculating the final value.

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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 that does not alter the chemical composition of a substance (e.g., melting, freezing).
Chemical Change: A change that results in the formation of new chemical substances.

Step-by-Step Guidance

Review each option and decide if the process involves a change in chemical composition or just a change in state/form.
Recall that melting, boiling, and dissolving (without reaction) are physical changes.
Identify the option that describes a physical change, not a chemical reaction.

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Q6. How is a gas characterized?

Background

Topic: States of Matter

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

Key Terms:

Definite Shape: Maintains its own shape (solids).
Definite Volume: Maintains its own volume (solids and liquids).
Indefinite Shape/Volume: Takes the shape and volume of its container (gases).

Step-by-Step Guidance

Recall the properties of gases: they expand to fill their container and do not have a fixed shape or volume.
Compare each option to the definition of a gas.
Select the option that matches the characteristics of a gas.

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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:

Pure Substance: Matter with a fixed composition (element or compound).
Mixture: Combination of two or more substances not chemically combined.
Compound: Substance composed of two or more elements chemically combined in a fixed ratio.

Step-by-Step Guidance

Note that vinegar contains both acetic acid and water in variable proportions.
Recall that mixtures can have variable composition, while compounds have fixed ratios.
Decide which classification best fits vinegar based on its 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:

Element: Substance that cannot be broken down into simpler substances by chemical means.
Compound: Substance composed of two or more elements chemically combined in a fixed ratio.
Mixture: Physical combination of substances with variable composition.

Step-by-Step Guidance

Recognize that table sugar (sucrose) always has the same composition, regardless of source.
Recall that compounds have a fixed ratio of elements.
Determine 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 basic definitions of elements and compounds.

Key Terms:

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

Step-by-Step Guidance

Recall the definition of an element.
Compare the options and select the one that matches the definition.

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Q10. Which of the following represents a compound?

Background

Topic: Elements vs. Compounds

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

Key Terms:

Compound: A substance formed when two or more elements are chemically bonded together.
Chemical Formula: Representation of the elements in a compound and their ratios.

Step-by-Step Guidance

Identify which formulas represent single elements and which represent combinations of elements.
Recall that compounds have more than one type of element in their formula.
Select the formula that fits the definition of a compound.