Chemistry Concepts

Question 1

A mixture consists of two or more substances physically combined, where each substance retains its own properties (e.g., salad, air, saltwater).

A pure substance is made of only one type of material, either an element or a compound, and has consistent properties throughout (e.g., oxygen, gold, water).

Answer 1

What is the difference between a mixture and a pure substance?

Question 2

A property is a characteristic of a substance that can be observed or measured, such as color, density, boiling point, or reactivity.

Answer 2

What is a property?

Question 3

A substance’s intrinsic properties (e.g., boiling point, density, color) do not depend on the amount of the substance.

Extrinsic properties (e.g., mass, volume) do depend on how much of the substance is present.

Answer 3

Does a substance’s properties depend on how much of the substance you have?

Question 4

Physical properties can be observed without changing the substance’s identity (e.g., color, melting point, density).

Chemical properties describe a substance’s ability to undergo chemical changes (e.g., flammability, reactivity with acid).

Answer 4

What is the difference between a physical property and a chemical property?

Question 5

Physical change: The substance changes form but remains the same substance (e.g., melting ice, tearing paper).

Chemical change: A new substance is formed with different properties (e.g., rusting iron, burning wood).

Answer 5

What is the difference between a physical change and a chemical change?

Question 6

Color change

Gas production (bubbles, odor change)

Formation of a precipitate (solid forms in a liquid)

Energy change (heat, light, sound released)

Answer 6

What evidence indicates that a chemical change has occurred?

Question 7

Proton: Charge = +1, Mass ≈ 1 atomic mass unit (amu)

Neutron: Charge = 0, Mass ≈ 1 amu

Electron: Charge = -1, Mass ≈ 0 amu (very tiny compared to protons and neutrons)

Answer 7

What is the charge and mass of the proton, the neutron, and the electron?

Question 8

Most matter is neutral, meaning it has equal numbers of protons and electrons.

Answer 8

What charge does matter most of the time?

Question 9

An atom is the smallest unit of an element that retains the properties of that element.

Answer 9

What is an atom?

Question 10

The atomic number represents the number of protons in an atom’s nucleus.

Answer 10

What is an atomic number?

Question 11

Metals lose electrons to form positive ions.

Answer 11

What do metals tend to do in chemical changes?

Question 12

Nonmetals gain electrons to form negative ions.

Answer 12

What do nonmetals tend to do in chemical changes?

Question 13

Groups (columns) are arranged by elements with similar properties and the same number of valence electrons.

Answer 13

How are groups on the periodic table?

Question 14

Atomic mass is the weighted average mass of an element’s isotopes, measured in atomic mass units (amu).

Answer 14

What is atomic mass?

Question 15

Protons and neutrons are in the nucleus.

Electrons orbit in electron shells around the nucleus.

Answer 15

Where is each particle (protons, neutrons, electrons) that makes up an atom found?

Question 16

Electron shells are energy levels where electrons are found around the nucleus.

Answer 16

What are electron shells?

Question 17

The atom becomes stable and less likely to react.

Answer 17

What happens when an atom’s outer shell of electrons is full?

Question 18

Noble gases have full outer electron shells, making them chemically stable and unreactive.

Answer 18

Why do noble gasses not react?

Question 19

Changing the number of electrons affects charge but not mass.

Answer 19

What happens to an atom’s charge and mass if the number of electrons changes?

Question 20

Changing the number of neutrons affects mass but not charge.

Answer 20

What happens to an atom’s charge and mass if the number of neutrons changes?

Question 21

A chemical formula represents the types and numbers of atoms in a compound (e.g., H₂O, CO₂).

Answer 21

What is a chemical formula?

Question 22

States that matter cannot be created or destroyed in a chemical reaction—mass remains constant.

Answer 22

What is the Law of Conservation of Mass?

Question 23

Observe whether the sample has uniform composition. If it has different components that can be separated physically, it is a mixture. If not, it is a pure substance.

Answer 23

How would you determine whether an example of matter is a mixture or a pure substance

Question 24

Determine if the characteristic involves a change in composition (chemical property) or if it can be observed without changing the substance (physical property).

Answer 24

How would you determine whether something is a physical property or a chemical property based on its description.

Question 25

Look for evidence of a chemical change like new substances forming, color change, gas production, or energy change (chemical change). If the material retains its identity, it’s a physical change.

Answer 25

How would you determine whether a change is physical or chemical based on evidence.

Question 26

Locate the element’s name, chemical symbol, atomic number, and atomic mass.

Answer 26

Using the Periodic Table, Find an element’s name, chemical symbol, atomic number, and atomic mass

Question 27

1. Find metalloids: A diagonal line from “B” to “At” with 3 below on the bottom.
2. To the right of this are the non-metals
3. To the left of this are the metals (most of the periodic table).

Answer 27

Using the Periodic Table, Determine whether an element is a metal, nonmetal, or metalloid

Question 28

Groups are the columns
- The group number tells you the number of valence electrons

Periods are the rows
- The period number tells you the electron levels an element has.

Answer 28

Using the Periodic Table, Determine to which group or period an element belongs.

Question 29

Draw the nucleus with the correct number of protons and neutrons jumbled together.

Use what you know about electrons (2, 8, 18, 32) to properly draw the circles around the nucleus.

Answer 29

Using the Periodic Table, Draw a model of an atom that shows the correct number of protons, neutrons, and electrons, as well as the location of each particle

Question 30

The correct number of atoms is the subscript (little number)

The number of total molecules is the big number (e.g., 2 water molecules)

Answer 30

Using the Periodic Table, Write a simple chemical formula, given the names of elements and numbers of atoms of each

Question 31

Count each element’s atoms from the subscripts in the formula.

Answer 31

Using the Periodic Table, Interpret a chemical formula to determine how many atoms of each element that compound contains.