A: Chemistry = Chemical Changes 1.3 Breaking Bonds

Question 1

What indicates that a chemical change is occurring?

Answer 1

A new substance is produced, accompanied by a change in colour, odour, state, or energy.

Question 2

What are the two types of energy changes during a chemical change?

Answer 2

• Exothermic: energy is released
• Endothermic: energy is absorbed

Question 3

Define chemical change.

Answer 3

A change in which one or more new substances with different properties is formed.

Question 4

What happens to bonds during a chemical change?

Answer 4

Bonds between atoms in the original substances are broken and new bonds are formed.

Question 5

Fill in the blank: An _______ change is a chemical change in which energy is released into the surroundings.

Answer 5

exothermic

Question 6

Fill in the blank: An _______ change is a chemical change in which energy is absorbed from the surroundings.

Answer 6

endothermic

Question 7

What usually accompanies changes in state during a chemical change?

Answer 7

The formation of a gas or a solid.

Question 8

True or False: Chemical changes can only occur with visible changes like colour or state.

Answer 8

False

Question 9

What type of energy change occurs when heat is absorbed?

Answer 9

Endothermic change.

Question 10

What type of energy change occurs when heat is released?

Answer 10

Exothermic change.

Question 11

What is a solution?

Answer 11

A mixture made up of more than one type of particle, where the particles intermingle with one another.

Question 12

How do solutions appear?

Answer 12

As though they are composed of only one substance, even though they contain more than one species within them.

Question 13

What is an aqueous solution?

Answer 13

A solution in which water is the solvent.

Question 14

What are the components of a solution?

Answer 14

A solute and a solvent.

Question 15

True or False: Most reactions occur when matter is dissolved in water.

Answer 15

True

Question 16

Fill in the blank: A solution is a _______ mixture of dissolved substances.

Answer 16

[homogeneous]

Question 17

What is a solute?

Answer 17

A substance in a solution whose bonds are broken by a solvent; a substance that dissolves

Examples include salt in saltwater or sugar in tea.

Question 18

What is a solvent?

Answer 18

A substance in a solution that breaks down the bonds of a solute; a substance that does the dissolving and is in greater proportion in the mixture

Water is often referred to as the universal solvent.

Question 19

What happens when a substance becomes dissolved?

Answer 19

Its bonds have been broken down, and the particles separate and move freely as individuals throughout the solution

This process can involve either molecules or ions.

Question 20

Fill in the blank: A _______ dissolves in a solvent.

Answer 20

[solute]

Question 21

Fill in the blank: A _______ is in greater proportion in a mixture and breaks down the bonds of a solute.

Answer 21

[solvent]

Question 22

What is the role of a solvent like water in chemical reactions?

Answer 22

A solvent helps break down certain types of bonds in a substance

Question 23

Why do many reactions naturally occur in solution?

Answer 23

Because solutes can be broken down into individual parts that are no longer bonded to other ions

Question 24

What happens when a solute is broken down in a solution?

Answer 24

The individual parts can collide with and form new bonds with other substances

Question 25

Fill in the blank: Water acts as a _______ to break chemical bonds.

Answer 25

solvent

Question 26

True or False: Once old bonds are broken, ions can no longer form new bonds.

Answer 26

False

Question 27

What is the shape of a water molecule?

Answer 27

Bent ## Footnote A three-dimensional diagram reveals that a water molecule has a bent shape.

Question 28

What causes the unequal sharing of electrons in a water molecule?

Answer 28

The difference in electronegativity between hydrogen and oxygen ## Footnote The oxygen atom tends to keep the shared pairs of electrons closer to itself.

Question 29

What is the result of the unequal sharing of electrons in a water molecule?

Answer 29

Partial charges ## Footnote The unequal sharing results in a partial negative charge on the oxygen atom and a partial positive charge on each hydrogen atom.

Question 30

What symbol represents a partial positive charge?

Answer 30

δ+ ## Footnote The symbol for a partial positive charge is read as delta positive.

Question 31

What symbol represents a partial negative charge?

Answer 31

δ- ## Footnote The symbol for a partial negative charge is read as delta negative.

Question 32

What is the charge distribution in a water molecule?

Answer 32

Partial positive charge on hydrogen atoms and partial negative charge on the oxygen atom ## Footnote The bent shape combined with the unequal sharing of electrons results in this charge distribution.

Question 33

True or False: A water molecule is neutral overall.

Answer 33

True ## Footnote Despite having partial charges, the overall water molecule is neutral.

Question 34

What is a polar molecule?

Answer 34

A molecule with a partial positive charge at one end and a partial negative charge at the other end. ## Footnote Water is an example of a polar molecule due to its uneven charge distribution.

Question 35

What causes the polar nature of water?

Answer 35

The uneven charge distribution within the water molecule. ## Footnote This results in one end of the molecule having a partial negative charge and the other end having a partial positive charge.

Question 36

What is the significance of water's polar nature?

Answer 36

It leads to many of water's special properties. ## Footnote These properties include high surface tension, solvent capabilities, and temperature regulation.

Question 37

What end of a water molecule has a partial negative charge?

Answer 37

The oxygen end. ## Footnote This is due to oxygen's higher electronegativity compared to hydrogen.

Question 38

What end of a water molecule has a partial positive charge?

Answer 38

The hydrogen end. ## Footnote This is a result of the hydrogen atoms being less electronegative than oxygen.

Question 39

Fill in the blank: Water is called a _______ molecule.

Answer 39

polar

Question 40

What is the charge of the positive end of a water molecule?

Answer 40

Delta positive so attracted to a negatively charged object

Question 41

What helps explain the attraction of water to a statically charged balloon?

Answer 41

Understanding the partial charges on a water molecule

Question 42

What produces static electrical charges?

Answer 42

Electrons are transferred

Question 43

What happens to a balloon when it is rubbed against your hair?

Answer 43

It becomes negatively charged

Question 44

What is drawn toward the negatively charged balloon?

Answer 44

The stream of water

Question 45

Fill in the blank: Water is a very powerful _______.

Answer 45

[solvent]

Question 46

Why can water dissolve most ionic crystals?

Answer 46

Because they are made up of positively and negatively charged ions

Question 47

Do all ionic compounds dissolve in water?

Answer 47

Yes, to some extent

Question 48

What varies among different ionic compounds in water?

Answer 48

Solubility

Question 49

What is the relationship between a molecular compound's charge and its ability to dissolve in water?

Answer 49

The ability to dissolve in water may be related to the compound's charge distribution, with uneven charge attracting water molecules. ## Footnote Molecules with equal charge distribution do not attract water and thus do not dissolve.

Question 50

Name a substance that does not dissolve in water due to its covalent bonds.

Answer 50

Triglyceride (a fat molecule) ## Footnote Triglycerides are examples of covalent compounds that are nonpolar and do not interact favorably with polar water molecules.

Question 51

Fill in the blank: Some substances held together by covalent bonds, like ________, do not dissolve in water.

Answer 51

oil ## Footnote Oil is a nonpolar substance and does not mix with polar solvents like water.

Question 52

True or False: All molecular compounds dissolve in water.

Answer 52

False ## Footnote Only molecular compounds with uneven charge distributions typically dissolve in water.

Question 53

What happens to water molecules when they interact with a molecular compound that has an uneven charge distribution?

Answer 53

Water molecules surround the charged particle and cause it to dissolve. ## Footnote This process is due to electrostatic attraction between the water molecules and the charged regions of the compound.

Question 54

Why are many industrial factories located near a source of water?

Answer 54

Plant processes often require large amounts of water for chemical reactions.

Question 55

What is the role of water in chemical industries?

Answer 55

Water effectively breaks down bonds and allows chemical reactions to occur.

Question 56

What happens when an ionic compound dissolves in water?

Answer 56

The bonds between ions within the ionic solid are broken by water molecules.

Question 57

What is the process called when an ionic compound breaks down into smaller parts?

Answer 57

Dissociation.

Question 58

What particles are produced when ionic compounds dissociate in solution?

Answer 58

Negatively charged and positively charged particles.

Question 59

What is the significance of having both negatively and positively charged particles in a solution?

Answer 59

The particles can move in response to other charged objects.

Question 60

What does a simple conductivity test involve?

Answer 60

Placing two electrodes of a conductivity apparatus in a solution.

Question 61

What happens to ions during a conductivity test?

Answer 61

Different charges attract different ions, allowing them to move toward one of the electrodes.

Question 62

What is the result of the movement of ions in a conductivity test?

Answer 62

It completes the electrical circuit of the conductivity meter.

Question 63

What are solutes that conduct an electrical current in a solution called?

Answer 63

Electrolytes.

Question 64

Fill in the blank: Dissociation is the separation of an ionic _______.

Answer 64

compound.

Question 65

What are dissociated ions in relation to conductivity?

Answer 65

Dissociated ions can move toward the oppositely charged electrodes of the conductivity meter.

Question 66

What completes the circuit of the conductivity meter?

Answer 66

The movement of ions (charges) completes the circuit of the conductivity meter.

Question 67

What is a non-electrolyte?

Answer 67

A substance that forms a non-conducting solution.

Question 68

Can water break covalent bonds in molecular compounds?

Answer 68

No, water cannot break the covalent bonds between atoms in molecular compounds.

Question 69

How do molecular compounds behave in water?

Answer 69

Molecular compounds do not dissociate; water separates the molecules from the other molecules if they have an uneven distribution of charge. Water will not separate the atom bonds in the molecule.

Question 70

What is the result of dissolving a molecular compound in water?

Answer 70

A solution of a molecular compound does not contain negative and positive ions.

Question 71

What happens to the electrical circuit when a molecular compound is dissolved?

Answer 71

The electrical circuit of the conductivity apparatus will not be completed.

Question 72

Fill in the blank: A molecular compound dissolving in water results in _______.

Answer 72

a non-conducting solution.

Question 73

Identify the type of compound: KBr(s)

Answer 73

Ionic compound

Question 74

Identify the type of compound: AgNO₃(s)

Answer 74

Ionic compound

Question 75

What ions would KBr dissociate into?

Answer 75

* K⁺ * Br⁻

Question 76

What ions would AgNO₃ dissociate into?

Answer 76

* Ag⁺ * NO₃⁻

Question 77

State whether KBr would be classified as an electrolyte or a non-electrolyte if added to water.

Answer 77

Electrolyte

Question 78

State whether AgNO₃ would be classified as an electrolyte or a non-electrolyte if added to water.

Answer 78

Electrolyte

Question 79

What are dissociated ions in relation to conductivity?

Answer 79

Dissociated ions can move toward the oppositely charged electrodes of the conductivity meter.

Question 80

What completes the circuit of the conductivity meter?

Answer 80

The movement of ions (charges) completes the circuit of the conductivity meter.

Question 81

What is a non-electrolyte?

Answer 81

A substance that forms a non-conducting solution.

Question 82

Can water break covalent bonds in molecular compounds?

Answer 82

No, water cannot break the covalent bonds between atoms in molecular compounds.

Question 83

How do molecular compounds behave in water?

Answer 83

Molecular compounds do not dissociate; water separates the molecules if they have an uneven distribution of charge.

Question 84

What is the result of dissolving a molecular compound in water?

Answer 84

A solution of a molecular compound does not contain negative and positive ions.

Question 85

What happens to the electrical circuit when a molecular compound is dissolved?

Answer 85

The electrical circuit of the conductivity apparatus will not be completed.

Question 86

Fill in the blank: A molecular compound dissolving in water results in _______.

Answer 86

a non-conducting solution.

Question 87

Identify the type of compound: KBr(s)

Answer 87

Ionic compound

Question 88

Identify the type of compound: AgNO₃(s)

Answer 88

Ionic compound

Question 89

What ions would KBr dissociate into?

Answer 89

* K⁺ * Br⁻

Question 90

What ions would AgNO₃ dissociate into?

Answer 90

* Ag⁺ * NO₃⁻

Question 91

State whether KBr would be classified as an electrolyte or a non-electrolyte if added to water.

Answer 91

Electrolyte

Question 92

State whether AgNO₃ would be classified as an electrolyte or a non-electrolyte if added to water.

Answer 92

Electrolyte