2A1 Structure and Properties of Matter

Question 1

Define:

atom

Answer 1

The smallest unit of matter that retains the properties of an element.

Atoms are the building blocks of all matter, forming the basis of elements and compounds.

Question 2

What are the two primary regions of an atom?

Answer 2

1. The nucleus
2. The electron cloud.

The nucleus is the dense central region of the atom, while the electron cloud surrounds it, defining the atom’s overall size and shape.

Question 3

What are the subatomic particles that make up an atom?

Answer 3

• Protons
• Neutrons
• Electrons

These particles are the building blocks of an atom, with protons and neutrons found in the nucleus, and electrons orbiting around it.

Protons: Positively charged particles in the nucleus.

Neutrons: Neutral particles in the nucleus.

Electrons: Negatively charged particles orbiting the nucleus.

Question 4

True or False:

The majority of an atom’s volume is occupied by the nucleus.

Answer 4

False

The majority of an atom’s volume is empty space, where the electrons move in orbitals around the nucleus.

Question 5

List the four basic atomic models developed by scientists.

Answer 5

1. Dalton’s model (1803)
2. Thomson’s model (1897)
3. Rutherford’s model (1911)
4. Bohr’s model (1913)

Question 6

True or False:

The Bohr model is still the most accurate model for electron behavior.

Answer 6

False

The Bohr model was replaced by the quantum mechanical model, which describes electron behavior more accurately.

Question 7

Which subatomic particle has a positive charge?

Answer 7

Protons

Protons are found in the nucleus and are responsible for the positive charge of the atom.

Question 8

How does the number of protons in an atom affect its chemical identity?

Answer 8

It determines the element and its position on the periodic table.

For example, an atom with one proton is hydrogen, and an atom with six protons is carbon.

Question 9

Define:

atomic mass

Answer 9

The total mass of an atom.

It is mainly determined by the sum of its protons and neutrons, often referred to as the mass number.

Question 10

Fill in the blank:

The number of protons in an atom is called its _____ _____.

Answer 10

atomic number

The atomic number is unique to each element and defines the element’s identity.

Question 11

True or False:

Electrons are located in fixed orbits around the nucleus.

Answer 11

False

Electrons are located in probabilistic orbitals, not fixed paths, based on quantum mechanics.

Question 12

What is an atom with a net charge due to the gain or loss of electrons?

Answer 12

Ion

Losing electrons creates a cation, gaining electrons creates an anion.

Question 13

What is the charge of a neutron?

Answer 13

They have no charge; they are neutral.

Neutrons play a role in stabilizing the nucleus by balancing the positive charge of protons.

Question 14

What are atoms of the same element with a different number of neutrons?

Answer 14

Isotopes

Isotopes have nearly identical chemical properties but different atomic masses.

Question 15

Why are isotopes of the same element chemically similar?

Answer 15

They have the same number of protons.

The number of protons determines the element’s chemical behavior, and since isotopes share the same electron configuration, their chemical properties are similar.

Question 16

Define:

radioactive isotope

Answer 16

An isotope that is unstable and undergoes radioactive decay over time.

Radioactive isotopes emit radiation as they decay into more stable forms.

Question 17

What isotope is commonly used for dating ancient objects?

Answer 17

Carbon-14

Carbon-14 decays at a known rate, making it useful for radiocarbon dating of organic materials.

Question 18

What is the role of carbon-14 in radiocarbon dating?

Answer 18

It decays over time, helping estimate an object’s age.

By measuring remaining carbon-14, scientists can date organic materials up to about 50,000 years old.

Question 19

List the types of radiation emitted by radioactive isotopes.

Answer 19

• Alpha particles
• Beta particles
• Gamma rays

Each type of radiation has different properties and applications in medicine, industry, and research.

Question 20

Define:

electron configuration

Answer 20

The arrangement of electrons in the orbitals of an atom.

The electron configuration determines an atom’s reactivity, stability, and its ability to form bonds with other atoms.

Question 21

What is the maximum electron capacity of the first three energy levels?

Answer 21

• First energy level: 2 electrons
• Second energy level: 8 electrons
• Third energy level: 18 electrons

Each energy level can hold a specific number of electrons, following the 2n² rule.

Question 22

What is the maximum number of electrons in the second energy level?

Answer 22

8

Each energy level can hold a specific number of electrons, and the second level holds up to 8 electrons.

Question 23

True or False:

Electrons in the outermost shell are known as valence electrons.

Answer 23

True

Valence electrons are involved in chemical bonding and determine the chemical reactivity of an atom.

Question 24

Define:

periodic table

Answer 24

A table of elements arranged by atomic number.

Rows (periods) show increasing atomic number, while columns (groups) contain elements with similar properties.

Question 25

What are the **three main categories** of elements in the periodic table?

Answer 25

1. Metals 1. Nonmetals 1. Metalloids

Question 26

What is a **group** in the periodic table?

Answer 26

A **column of elements** with similar properties. ## Footnote Groups are numbered 1 to 18 and are often defined by the *number of valence electrons*.

Question 27

# Fill in the blank: A \_\_\_\_\_\_ is a **horizontal row of elements** with the same electron shells.

Answer 27

period ## Footnote As you move across a **period**, the number of protons and electrons increases.

Question 28

What are **alkali metals**?

Answer 28

**Highly reactive elements** in Group 1 with one valence electron. ## Footnote Alkali metals include *lithium*, *sodium*, and *potassium*, and react vigorously with water.

Question 29

What **group** has two valence electrons and moderate reactivity?

Answer 29

Alkaline earth metals ## Footnote These elements, such as *magnesium* and *calcium*, are commonly found in minerals and compounds.

Question 30

# True or False: Noble gases are **highly reactive**.

Answer 30

False ## Footnote Noble gases have *full valence shells*, making them chemically inert and non-reactive.

Question 31

Why are noble gases **considered** chemically inert?

Answer 31

They have a **complete set** of valence electrons. ## Footnote This makes them **stable** and unlikely to bond with other elements.

Question 32

What are **transition metals**?

Answer 32

Elements with **high melting points** and **good conductivity**. ## Footnote Transition metals are found in *Groups 3 to 12* and include iron, copper, and gold.

Question 33

What group **contains** the halogens?

Answer 33

Group 17 ## Footnote **Halogens** include fluorine, chlorine, bromine, iodine, and astatine.

Question 34

# True or False: Alkaline earth metals are **less reactive** than alkali metals.

Answer 34

True ## Footnote *Alkaline earth metals* have two valence electrons, making them less reactive than alkali metals with one valence electron.

Question 35

What **group** contains the alkaline earth metals?

Answer 35

2 ## Footnote *Alkaline earth metals* include beryllium, magnesium, calcium, strontium, barium, and radium.

Question 36

What **group** contains the alkali metals?

Answer 36

1 ## Footnote *Alkali metals* include lithium, sodium, potassium, rubidium, cesium, and francium. They are highly reactive and have one valence electron.

Question 37

# Define: matter

Answer 37

nAnything that **has mass** and **occupies space**. ## Footnote **Matter** is composed of atoms and can exist in different states, including solid, liquid, and gas.

Question 38

What are the *three* **main states of matter**?

Answer 38

1. Solid 1. Liquid 1. Gas ## Footnote **Solid**: Definite shape and volume. **Liquid**: Definite volume but no definite shape. **Gas**: No definite shape or volume.

Question 39

How does the particle motion **differ** between solids, liquids, and gases?

Answer 39

* **Solids**: Particles vibrate in place. * **Liquids**: Particles move around each other. * **Gases**: Particles move freely.

Question 40

# True or False: The motion of particles in a solid is **faster** than that in a liquid.

Answer 40

False ## Footnote Particles in solids move **slower** because they are closely packed and only vibrate in place.

Question 41

Why do particles in a gas **move freely**?

Answer 41

They have **high kinetic energy** and are **far apart**. ## Footnote This allows them to move independently, filling the available space and giving gases no definite shape or volume.

Question 42

What happens when the **temperature** of a liquid is lowered?

Answer 42

The particles move **slower** and may **freeze**. ## Footnote This is due to a *decrease in kinetic energy*, causing the particles to form a fixed arrangement.

Question 43

How does an increase in temperature affect the particles in a **solid**?

Answer 43

It causes particles to **vibrate more** and may transition to a **liquid**. ## Footnote The increased energy raises kinetic energy, making particles vibrate faster, eventually breaking the bonds between them.

Question 44

How does an increase in temperature affect the particles in a **liquid**?

Answer 44

Particles **move faster** and may become a **gas**. ## Footnote This is due to increased energy allowing particles to overcome intermolecular forces, leading to evaporation or boiling.

Question 45

How does an increase in temperature affect the particles in a **gas**?

Answer 45

Particles move faster and **spread out**. ## Footnote The increase in kinetic energy causes faster movement and greater particle separation, raising pressure if the volume is constant.

Question 46

What are the *two* **main types** of pure substances?

Answer 46

* Elements * Compounds ## Footnote Both are considered *pure substances* because they are made up of only *one type of particle.*

Question 47

What is the **simplest form of matter** that cannot be broken down further?

Answer 47

An element ## Footnote **Elements** are listed in the periodic table and consist of atoms with the same number of protons.

Question 48

# Fill in the blank: A \_\_\_\_\_\_ is a substance made of **two** or more elements.

Answer 48

compound ## Footnote The elements combine in fixed ratios, and **compounds** have different properties from the elements that form them. **Water** is a compound made of hydrogen and oxygen atoms in a 2:1 ratio.

Question 49

# True or False: A mixture is a **combination** of substances separable physically.

Answer 49

True ## Footnote **Mixtures** retain the properties of their individual components.

Question 50

What is the **key difference** between a compound and a mixture?

Answer 50

Compounds are **chemically bonded**, while mixtures are not. ## Footnote In mixtures, the components retain their individual properties, unlike in compounds. *Saltwater* is a mixture, while *water and sodium chloride (salt)* together form a compound.

Question 51

What is a **heterogeneous mixture**?

Answer 51

A mixture with components that are **not uniformly** distributed. ## Footnote These components can often be seen and separated **physically**, like in granite and salad dressing.

Question 52

What type of mixture has components that are **uniformly** distributed?

Answer 52

Homogeneous mixture ## Footnote In a *homogeneous mixture*, the composition is consistent throughout, such as in solutions like saltwater.

Question 53

What **type of mixture** is sand and water?

Answer 53

Heterogeneous mixture ## Footnote In this mixture, sand and water are *not uniformly mixed*, and the sand can be separated from the water.

Question 54

What **method** can be used to separate a solid from a liquid in a mixture?

Answer 54

Filtration ## Footnote **Filtration** separates solid particles from liquids using a filter paper or other porous materials.

Question 55

# True or False: A solution is a type of **homogeneous mixture**.

Answer 55

True ## Footnote A **solution** is a homogeneous mixture where one substance is dissolved in another, such as salt dissolved in water.

Question 56

What is the substance that is **dissolved** in a solution?

Answer 56

Solute ## Footnote In a saltwater solution, salt is the **solute**, and water is the **solvent**.

Question 57

What is the **role** of the solvent in a solution?

Answer 57

It **dissolves** the solute to form a solution. ## Footnote The solvent usually makes up the larger portion of the solution.

Question 58

What is the **difference** between a saturated and an unsaturated solution?

Answer 58

* **Saturated solution**: No more solute can dissolve at a given temperature. * **Unsaturated solution**: More solute can still dissolve at a given temperature.

Question 59

What is the **difference** between a dilute and a concentrated solution?

Answer 59

* **Dilute solution**: Has a small amount of solute compared to the solvent. * **Concentrated solution**: Has a large amount of solute compared to the solvent

Question 60

# Define: acid

Answer 60

A substance that **donates hydrogen ions (H+)** when dissolved in water. ## Footnote **Acids** have a pH less than 7 and are typically sour in taste (e.g., hydrochloric acid, citric acid).

Question 61

What is a substance that **accepts H+ ions** or releases OH- ions in water?

Answer 61

Base ## Footnote **Bases** have a pH greater than 7 and are slippery and bitter in taste (e.g., sodium hydroxide, ammonia).

Question 62

# True or False: Bases have a pH **less** than 7.

Answer 62

False ## Footnote Bases have a pH **greater** than 7, while acids have a pH less than 7.

Question 63

What is the **pH scale**?

Answer 63

It **measures** how acidic or basic a solution is. ## Footnote It ranges from 0 (acidic) to 14 (basic), with 7 being neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic.

Question 64

# Fill in the blank: A pH of \_\_\_\_\_ indicates a **neutral solution**.

Answer 64

7 ## Footnote Pure water is considered neutral with a pH of 7.

Question 65

List the **factors** that affect the rate of dissolving.

Answer 65

* Temperature * Particle size * Stirring ## Footnote **Temperature**: Increasing temperature generally increases the rate of dissolving. **Particle size**: Smaller particles dissolve faster due to increased surface area. **Stirring**: Stirring speeds up dissolving by bringing fresh solvent into contact with solute.

Question 66

What is the **chemical formula** for water?

Answer 66

H₂O ## Footnote The formula represents *two hydrogen atoms* bonded to *one oxygen atom* in a molecule of water.

Question 67

What **type of bond** is formed in sodium chloride (NaCl)?

Answer 67

Ionic bond ## Footnote In **NaCl**, sodium gives up an electron to chlorine, forming oppositely charged ions.

Question 68

Why do **ionic compounds** have high melting and boiling points?

Answer 68

They have **strong forces** between charged ions. ## Footnote These strong forces require a lot of energy to break, resulting in high melting and boiling points, as seen in sodium chloride.

Question 69

# Define: covalent bond

Answer 69

It is a chemical bond where two atoms **share** electrons. ## Footnote *Water (H₂O)* is a common example, with hydrogen and oxygen sharing electrons.

Question 70

# Fill in the blank: In a **covalent bond**, electrons are \_\_\_\_\_\_\_ between two atoms.

Answer 70

shared ## Footnote In a covalent bond, electrons are shared to achieve a **stable** electron configuration.

Question 71

Which bond is responsible for the **electrical conductivity** in metals?

Answer 71

Metallic ## Footnote *Metallic bonds* allow for the free movement of electrons, similar to how an unsaturated solution can dissolve more solute without reaching its capacity.

Question 72

Why are **metals** good conductors of electricity?

Answer 72

The *sea of electrons* allows electrons to move freely. ## Footnote This enables the flow of *electrical current*, which is why metals like copper and aluminum are used in **wiring**.

Question 73

# True or False: Ionic bonds form **between** nonmetals and nonmetals.

Answer 73

False ## Footnote *Ionic bonds* typically form between **metals** and **nonmetals**, where one atom gives up an electron and the other accepts it.

Question 74

What **type of bond** is formed between two nonmetals?

Answer 74

Covalent ## Footnote Nonmetals share electrons to achieve stable electron configurations, forming *covalent bonds.*

Question 75

What is the **difference** between ionic, covalent, and metallic bonds?

Answer 75

* **Ionic bonds**: Electrons are transferred between atoms. * **Covalent bonds**: Electrons are shared between atoms. * **Metallic bonds**: Electrons move freely in a "sea" around atoms.

Question 76

What is a **phase change**?

Answer 76

The **transformation** of a substance from one state of matter to another. ## Footnote Examples of phase changes include melting (solid to liquid), freezing (liquid to solid), and vaporization (liquid to gas).

Question 77

What **phase change** occurs when a solid turns into a liquid?

Answer 77

Melting ## Footnote **Melting** occurs when heat is added to a solid, increasing its particle movement until it becomes a liquid.

Question 78

What is the **opposite** of melting?

Answer 78

Freezing ## Footnote **Freezing** is the process where a liquid loses heat and turns into a solid. For example, water freezes into ice when the temperature drops below 0°C.

Question 79

What is the **phase change** from liquid to gas at the surface?

Answer 79

Evaporation ## Footnote **Evaporation** occurs when particles at the surface of the liquid gain enough energy to escape into the gas phase.

Question 80

What **phase change** occurs when a liquid turns into a gas?

Answer 80

Vaporization ## Footnote **Vaporization** can occur *through boiling* (when a liquid is heated to its boiling point) or evaporation (when molecules at the surface of a liquid gain enough energy to escape into the air).

Question 81

# Define: Condensation

Answer 81

The **process** where a gas turns into a liquid upon cooling. ## Footnote For example, water vapor in the air condenses into *liquid water* on a cold surface, like a glass of ice-cold water.

Question 82

# True or False: Cooling a gas will **cause** condensation.

Answer 82

True ## Footnote **Cooling** reduces the energy of gas particles, causing them to *slow down* and condense into a liquid.

Question 83

# Fill in the blank: The **process** called when a solid turns directly into a gas is \_\_\_\_\_\_\_\_.

Answer 83

sublimation ## Footnote **Sublimation** occurs when a solid gains enough energy to bypass the liquid phase and turn directly into a gas, such as in dry ice (solid CO₂).

Question 84

What **phase change** occurs when a gas turns into a solid?

Answer 84

Deposition ## Footnote **Deposition** is the opposite of sublimation and occurs when gas particles lose energy and directly form a solid.

Question 85

# Define: cooling curve

Answer 85

It **shows** how temperature changes as a substance **cools**. ## Footnote It illustrates phase changes like *freezing* and *condensation*, with plateaus similar to a heating curve.

Question 86

# Define: heating curve

Answer 86

It **shows** the temperature of a substance as it is **heated**. ## Footnote It illustrates changes in state and temperature, with **plateaus** where phase changes like *melting* and *boiling* occur.

Question 87

# True or False: The temperature of a substance **increases** during melting.

Answer 87

False ## Footnote During melting, the temperature *remains constant* as the substance absorbs heat to overcome the forces holding the particles in place.