A: Chemistry = Chemical Changes 1.3 Breaking Bonds Flashcards
What indicates that a chemical change is occurring?
A new substance is produced, accompanied by a change in colour, odour, state, or energy.
What are the two types of energy changes during a chemical change?
- Exothermic: energy is released
- Endothermic: energy is absorbed
Define chemical change.
A change in which one or more new substances with different properties is formed.
What happens to bonds during a chemical change?
Bonds between atoms in the original substances are broken and new bonds are formed.
Fill in the blank: An _______ change is a chemical change in which energy is released into the surroundings.
exothermic
Fill in the blank: An _______ change is a chemical change in which energy is absorbed from the surroundings.
endothermic
What usually accompanies changes in state during a chemical change?
The formation of a gas or a solid.
True or False: Chemical changes can only occur with visible changes like colour or state.
False
What type of energy change occurs when heat is absorbed?
Endothermic change.
What type of energy change occurs when heat is released?
Exothermic change.
What is a solution?
A mixture made up of more than one type of particle, where the particles intermingle with one another.
How do solutions appear?
As though they are composed of only one substance, even though they contain more than one species within them.
What is an aqueous solution?
A solution in which water is the solvent.
What are the components of a solution?
A solute and a solvent.
True or False: Most reactions occur when matter is dissolved in water.
True
Fill in the blank: A solution is a _______ mixture of dissolved substances.
[homogeneous]
What is a solute?
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.
What is a solvent?
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.
What happens when a substance becomes dissolved?
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.
Fill in the blank: A _______ dissolves in a solvent.
[solute]
Fill in the blank: A _______ is in greater proportion in a mixture and breaks down the bonds of a solute.
[solvent]
What is the role of a solvent like water in chemical reactions?
A solvent helps break down certain types of bonds in a substance
Why do many reactions naturally occur in solution?
Because solutes can be broken down into individual parts that are no longer bonded to other ions
What happens when a solute is broken down in a solution?
The individual parts can collide with and form new bonds with other substances
Fill in the blank: Water acts as a _______ to break chemical bonds.
solvent
True or False: Once old bonds are broken, ions can no longer form new bonds.
False
What is the shape of a water molecule?
Bent
A three-dimensional diagram reveals that a water molecule has a bent shape.
What causes the unequal sharing of electrons in a water molecule?
The difference in electronegativity between hydrogen and oxygen
The oxygen atom tends to keep the shared pairs of electrons closer to itself.
What is the result of the unequal sharing of electrons in a water molecule?
Partial charges
The unequal sharing results in a partial negative charge on the oxygen atom and a partial positive charge on each hydrogen atom.
What symbol represents a partial positive charge?
δ+
The symbol for a partial positive charge is read as delta positive.
What symbol represents a partial negative charge?
δ-
The symbol for a partial negative charge is read as delta negative.
What is the charge distribution in a water molecule?
Partial positive charge on hydrogen atoms and partial negative charge on the oxygen atom
The bent shape combined with the unequal sharing of electrons results in this charge distribution.
True or False: A water molecule is neutral overall.
True
Despite having partial charges, the overall water molecule is neutral.
What is a polar molecule?
A molecule with a partial positive charge at one end and a partial negative charge at the other end.
Water is an example of a polar molecule due to its uneven charge distribution.
What causes the polar nature of water?
The uneven charge distribution within the water molecule.
This results in one end of the molecule having a partial negative charge and the other end having a partial positive charge.
What is the significance of water’s polar nature?
It leads to many of water’s special properties.
These properties include high surface tension, solvent capabilities, and temperature regulation.
What end of a water molecule has a partial negative charge?
The oxygen end.
This is due to oxygen’s higher electronegativity compared to hydrogen.
What end of a water molecule has a partial positive charge?
The hydrogen end.
This is a result of the hydrogen atoms being less electronegative than oxygen.
Fill in the blank: Water is called a _______ molecule.
polar
What is the charge of the positive end of a water molecule?
Delta positive so attracted to a negatively charged object
What helps explain the attraction of water to a statically charged balloon?
Understanding the partial charges on a water molecule
What produces static electrical charges?
Electrons are transferred
What happens to a balloon when it is rubbed against your hair?
It becomes negatively charged
What is drawn toward the negatively charged balloon?
The stream of water
Fill in the blank: Water is a very powerful _______.
[solvent]
Why can water dissolve most ionic crystals?
Because they are made up of positively and negatively charged ions
Do all ionic compounds dissolve in water?
Yes, to some extent
What varies among different ionic compounds in water?
Solubility
What is the relationship between a molecular compound’s charge and its ability to dissolve in water?
The ability to dissolve in water may be related to the compound’s charge distribution, with uneven charge attracting water molecules.
Molecules with equal charge distribution do not attract water and thus do not dissolve.
Name a substance that does not dissolve in water due to its covalent bonds.
Triglyceride (a fat molecule)
Triglycerides are examples of covalent compounds that are nonpolar and do not interact favorably with polar water molecules.
Fill in the blank: Some substances held together by covalent bonds, like ________, do not dissolve in water.
oil
Oil is a nonpolar substance and does not mix with polar solvents like water.
True or False: All molecular compounds dissolve in water.
False
Only molecular compounds with uneven charge distributions typically dissolve in water.
What happens to water molecules when they interact with a molecular compound that has an uneven charge distribution?
Water molecules surround the charged particle and cause it to dissolve.
This process is due to electrostatic attraction between the water molecules and the charged regions of the compound.
Why are many industrial factories located near a source of water?
Plant processes often require large amounts of water for chemical reactions.
What is the role of water in chemical industries?
Water effectively breaks down bonds and allows chemical reactions to occur.
What happens when an ionic compound dissolves in water?
The bonds between ions within the ionic solid are broken by water molecules.
What is the process called when an ionic compound breaks down into smaller parts?
Dissociation.
What particles are produced when ionic compounds dissociate in solution?
Negatively charged and positively charged particles.
What is the significance of having both negatively and positively charged particles in a solution?
The particles can move in response to other charged objects.
What does a simple conductivity test involve?
Placing two electrodes of a conductivity apparatus in a solution.
What happens to ions during a conductivity test?
Different charges attract different ions, allowing them to move toward one of the electrodes.
What is the result of the movement of ions in a conductivity test?
It completes the electrical circuit of the conductivity meter.
What are solutes that conduct an electrical current in a solution called?
Electrolytes.
Fill in the blank: Dissociation is the separation of an ionic _______.
compound.
What are dissociated ions in relation to conductivity?
Dissociated ions can move toward the oppositely charged electrodes of the conductivity meter.
What completes the circuit of the conductivity meter?
The movement of ions (charges) completes the circuit of the conductivity meter.
What is a non-electrolyte?
A substance that forms a non-conducting solution.
Can water break covalent bonds in molecular compounds?
No, water cannot break the covalent bonds between atoms in molecular compounds.
How do molecular compounds behave in water?
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.
What is the result of dissolving a molecular compound in water?
A solution of a molecular compound does not contain negative and positive ions.
What happens to the electrical circuit when a molecular compound is dissolved?
The electrical circuit of the conductivity apparatus will not be completed.
Fill in the blank: A molecular compound dissolving in water results in _______.
a non-conducting solution.
Identify the type of compound: KBr(s)
Ionic compound
Identify the type of compound: AgNO₃(s)
Ionic compound
What ions would KBr dissociate into?
- K⁺
- Br⁻
What ions would AgNO₃ dissociate into?
- Ag⁺
- NO₃⁻
State whether KBr would be classified as an electrolyte or a non-electrolyte if added to water.
Electrolyte
State whether AgNO₃ would be classified as an electrolyte or a non-electrolyte if added to water.
Electrolyte
What are dissociated ions in relation to conductivity?
Dissociated ions can move toward the oppositely charged electrodes of the conductivity meter.
What completes the circuit of the conductivity meter?
The movement of ions (charges) completes the circuit of the conductivity meter.
What is a non-electrolyte?
A substance that forms a non-conducting solution.
Can water break covalent bonds in molecular compounds?
No, water cannot break the covalent bonds between atoms in molecular compounds.
How do molecular compounds behave in water?
Molecular compounds do not dissociate; water separates the molecules if they have an uneven distribution of charge.
What is the result of dissolving a molecular compound in water?
A solution of a molecular compound does not contain negative and positive ions.
What happens to the electrical circuit when a molecular compound is dissolved?
The electrical circuit of the conductivity apparatus will not be completed.
Fill in the blank: A molecular compound dissolving in water results in _______.
a non-conducting solution.
Identify the type of compound: KBr(s)
Ionic compound
Identify the type of compound: AgNO₃(s)
Ionic compound
What ions would KBr dissociate into?
- K⁺
- Br⁻
What ions would AgNO₃ dissociate into?
- Ag⁺
- NO₃⁻
State whether KBr would be classified as an electrolyte or a non-electrolyte if added to water.
Electrolyte
State whether AgNO₃ would be classified as an electrolyte or a non-electrolyte if added to water.
Electrolyte
