Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout, such as saltwater.

Question 2

According to the scientific method, what is the correct sequence of steps when investigating a new phenomenon?

Accepted Answer

Observation → Hypothesis → Experiment → Law/Theory

Question 3

Which of the following statements about scientific laws and theories is correct?

Accepted Answer

A scientific law summarizes observed patterns, while a theory explains why those patterns occur.

Question 4

A student observes that a metal sample reacts with acid to produce hydrogen gas. Which step of the scientific method is this?

Accepted Answer

Observation

Question 5

Which of the following is an example of a compound?

Accepted Answer

Water ($$\mathrm{H_2O})$$

Question 6

Based on the table of hydrogen and oxygen masses, what is the approximate ratio of the mass of oxygen to hydrogen in water?

Accepted Answer

$$8:1$$

Question 7

Which of the following best explains why a theory can never be proven absolutely true?

Accepted Answer

A single experiment can disprove a theory, but no amount of experiments can prove it absolutely.

Question 8

Which method would you use to separate a mixture of sand and salt?

Accepted Answer

Physical methods, such as filtration and evaporation.

Question 9

Which of the following is NOT a step in the scientific method?

Accepted Answer

Ignoring data that does not fit your hypothesis.

Question 10

The graph of atmospheric carbon dioxide shows a sharp increase after 1950. What is the best scientific approach to investigate the cause?

Accepted Answer

Formulate a hypothesis about possible causes, then design experiments or collect data to test the hypothesis.

Question 11

Which of the following is a correct statement about elements and compounds?

Accepted Answer

Elements cannot be separated into simpler substances by chemical methods, but compounds can.

Question 12

A student claims that air is a compound. Which argument best refutes this claim?

Accepted Answer

Air is a mixture because its components can be separated by physical methods.

Question 13

Which of the following best describes the difference between a hypothesis and a theory?

Accepted Answer

A hypothesis is a tentative explanation, while a theory is a well-tested explanation supported by evidence.

Question 14

Which of the following is an example of applying the scientific method to a real-world problem?

Accepted Answer

Testing different cleaning agents to determine which removes stains most effectively.

Question 15

Which of the following best describes matter?

Accepted Answer

Anything that occupies space and has mass.

Question 16

A scientist observes a pattern in experimental data and creates a statement that predicts future results. What has the scientist created?

Accepted Answer

A scientific law

Question 17

Which of the following is a heterogeneous mixture?

Accepted Answer

Salad

Question 18

Which of the following best explains why graphing data is useful in scientific investigations?

Accepted Answer

It helps to identify patterns and trends that may not be obvious from raw data.

Question 19

Which of the following is an example of a physical method of separation?

Accepted Answer

Distillation of alcohol from water

Question 20

A student analyzes the mass ratio of oxygen to hydrogen in three samples of water and finds it is always about 8:1. What scientific principle does this illustrate?

Accepted Answer

Law of definite proportions

Chapter 1: The Chemical World – Foundations of Chemistry

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