Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture with a uniform composition throughout, such as salt dissolved in water.

Question 2

A sample of matter is composed of two elements chemically combined in a fixed ratio. Which classification best fits this sample?

Accepted Answer

Compound

Question 3

Which statement correctly compares the arrangement and movement of particles in solids, liquids, and gases?

Accepted Answer

In solids, particles are tightly packed and vibrate in place; in liquids, particles are close together but can slide past one another; in gases, particles are far apart and move randomly and rapidly.

Question 4

Which subatomic particle has a relative mass of approximately $1\ \mathrm{amu}$ and no electrical charge?

Accepted Answer

Neutron

Question 5

A neutral atom of an element has an atomic number $Z = 8$ and a mass number $A = 18$. How many neutrons does this atom have?

Accepted Answer

$10$

Question 6

Which of the following best defines the atomic number ($Z$) of an element?

Accepted Answer

The number of protons in the nucleus of an atom.

Question 7

A student mixes oil and water in a beaker. After a few minutes, two distinct layers form. How should this mixture be classified?

Accepted Answer

Heterogeneous mixture

Question 8

Which of the following statements about electrons is correct?

Accepted Answer

Electrons have a relative charge of $-1$ and a mass close to $0\ \mathrm{amu}$.

Question 9

Which of the following is an example of a compound?

Accepted Answer

Water ($\mathrm{H_2O}$)

Question 10

A sample contains only gold atoms. Which classification best describes this sample?

Accepted Answer

Element

Question 11

A chemist analyzes a sample and finds it contains sodium ions and chloride ions in a fixed 1:1 ratio, chemically bonded. Which classification best fits this sample?

Accepted Answer

Compound

Question 12

Which of the following best describes the difference between atomic mass and mass number?

Accepted Answer

Atomic mass is the weighted average mass of all naturally occurring isotopes of an element, while mass number is the sum of protons and neutrons in a specific atom.

Question 13

A neutral atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number ($A$)?

Accepted Answer

$35$

Question 14

Which of the following real-world scenarios best illustrates a heterogeneous mixture?

Accepted Answer

A salad with lettuce, tomatoes, and cucumbers.

Question 15

If an atom has 12 protons, 12 neutrons, and 12 electrons, what is its atomic number ($Z$) and mass number ($A$)?

Accepted Answer

$Z = 12$, $A = 24$

Question 16

Which of the following best explains why the atomic mass of an element is not always a whole number?

Accepted Answer

It is a weighted average of the masses of all naturally occurring isotopes of the element.

Question 17

A student observes that a sample of air appears uniform throughout and cannot see any separate components. How should air be classified?

Accepted Answer

Homogeneous mixture

Question 18

Which of the following statements about protons is correct?

Accepted Answer

Protons have a relative charge of $+1$ and are located in the nucleus.

Question 19

Which of the following best describes a mixture?

Accepted Answer

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

Question 20

A sample of matter is analyzed and found to have a uniform composition, but it can be separated into its components by physical means. Which classification best fits this sample?

Accepted Answer

Homogeneous mixture

Classification of Matter and Atomic Structure

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