unit 1

Question 1

thermoregulation

Answer 1

The study of energy changes involved in physical and chemical processes.

Question 2

First law of thermodynamics

Answer 2

The total energy of the universe is constant
Energy cannot be created or destroyed, only transformed from one substance to another and converted into various forms.

Question 3

Potential energy:

Answer 3

Stored energy as a result of position or composition
Has the potential to do work

Question 4

kinetic energy

Answer 4

Energy of motion
Energy AT WORK as a result of its motion.

Question 5

thermal energy

Answer 5

internal energy of a substance due to the kinetic energy of its atoms and/ or molecules and chemical composition(bonds)

Question 6

heat

Answer 6

amount of kinetic energy transferred between substances. Thus…an object CANNOT possess heat, only thermal energy.

Question 7

Temperature

Answer 7

A measure of the average kinetic energy of entities in a substance

Question 8

As particles move faster,

Answer 8

substance warms and vice versa

Question 9

System

Answer 9

The part of the universe being studied.

In a chemical reaction, the system includes reactants and products.

Question 10

Surroundings

Answer 10

Everything outside the system.

Essentially, the rest of the universe besides the system.

Question 11

enthalpy

Answer 11

The total thermal energy (kinetic + potential) of a system at constant pressure.
Enthalpy cannot be measured absolutely, only enthalpy changes can be studied.

Question 12

Enthalpy Change (ΔH)

Answer 12

Energy absorbed or released as the system changes from reactants to products.
Formula: ΔH = Hproducts - Hreactants

Question 13

endothermic

Answer 13

Energy is absorbed.
Hproducts > Hreactants, so ΔH > 0 (positive).

Question 14

exothermic

Answer 14

Energy is released.
Hproducts < Hreactants, so ΔH < 0 (negative).

Question 15

Molar Enthalpy Changes (ΔHx)

Answer 15

The enthalpy change for a physical, chemical, or nuclear change involving 1 mole of a substance.
Determined experimentally (empirically).

Question 16

What is a Calorimeter?

Answer 16

a device used to measure heat flow (enthalpy change) associated with a chemical or physical process.

Question 17

1. Simple (Coffee Cup) Calorimeter

Answer 17

Measures enthalpy change at constant pressure (open to atmosphere).
Water = surroundings.
Styrofoam insulates the system and immediate surroundings from greater surroundings.

Question 18

2. Bomb Calorimeter

Answer 18

Measures enthalpy change at constant volume.
The bomb (steel chamber) transfers heat to surrounding water.
The insulating container prevents heat exchange with the environment.

Question 19

Assumptions in Calorimetry

Answer 19

No heat is lost between the calorimeter and the environment.
Heat absorbed or released by the calorimeter itself is negligible.
A dilute aqueous solution behaves like pure water:
Density

Question 20

Energy Relationship (System & Surroundings)

Answer 20

Magnitude of heat transferred is the same, but the sign is opposite.

Question 21

Restricting the Surroundings in Calorimetry

Answer 21

Water represents the surroundings in calorimetry.
Exothermic reaction → Water absorbs energy.
Endothermic reaction → Water provides energy.

Dilute aqueous solution absorbs/releases energy → acts as both system & surroundings.

Question 22

Why Use Hess’s Law?

Answer 22

Some reactions release too much energy or occur too slowly for simple calorimetry.
Hess’s Law allows enthalpy change (Δ𝐻) to be determined without directly measuring it.

Question 23

What is Chemical Kinetics?

Answer 23

The study of reaction rates and the mechanisms by which reactions occur.
Focuses on how to speed up or slow down chemical reactions.

Question 24

Rate of Reaction

Answer 24

Determined by measuring:
- Rate of product formation
- Rate of reactant consumption
Measurable Properties:

Concentration
Mass
Colour
Conductivity
Volume
Pressure

Question 25

Average Rate of Reaction Formula

Answer 25

Average Rate= Change in concentration/Elapsed time ​ Units: mol/L·s

Question 26

Concentration Changes During a Reaction

Answer 26

Reaction rate is faster at the beginning and slows down over time. Graphing reaction data helps determine: Average rate of reaction Instantaneous rate of reaction

Question 27

Representing Reaction Rates

Answer 27

Reactants: Have a negative sign (concentration decreases over time). Products: Have a positive sign (concentration increases over time).

Question 28

Collision Theory

Answer 28

Particles are in constant random motion. Reactions occur when particles collide.

Question 29

Types of Collisions:

Answer 29

Effective Collisions – Have sufficient energy & correct orientation, leading to a reaction. Ineffective Collisions – Lack energy or proper orientation, so no reaction occurs.

Question 30

Factors Affecting Reaction Rate

Answer 30

Frequency of collisions (more collisions = faster reaction). Fraction of effective collisions (higher fraction = faster reaction).

Question 31

Effective Collision Criteria

Answer 31

Correct Orientation Reactant molecules must collide with the right geometry. Sufficient Energy Particles must have enough energy to break old bonds & form new ones.

Question 32

Energy Requirements for a Reaction

Answer 32

Threshold Energy: Minimum kinetic energy needed for a reaction to occur. Activation Energy (𝐸𝑎): Extra energy required to overcome the energy barrier.

Question 33

Transition State Theory

Answer 33

Explains how molecules transition from reactants to products. Kinetic energy converts to potential energy during a reaction

Question 34

Factors That Affect Reaction Rate

Answer 34

Chemical nature of reactants Concentration of reactants/products Surface area of reactants Temperature of the system Presence of a catalyst

Question 35

Chemical Nature of Reactants

Answer 35

Rate depends on: Bond strength (stronger bonds → slower reaction). Molecular complexity (more complex → slower reaction). Threshold energy (higher energy required → slower reaction). Chemical Kinetics: Affects the fraction of effective collisions.

Question 36

Concentration & Pressure

Answer 36

Higher concentration = more particles = more collisions = faster reaction. In gases, increasing pressure = increasing concentration. Chemical Kinetics: Affects the collision frequency.

Question 37

surface Area (Heterogeneous Reactions Only)

Answer 37

Reactions occur at the surface of solids. Larger surface area = more collisions = faster reaction. Chemical Kinetics: Affects the collision frequency.

Question 38

Temperature

Answer 38

Higher temperature = particles move faster & collide more forcefully. Increases: Collision frequency Fraction of effective collisions Chemical Kinetics: Affects both.

Question 39

Catalyst

Answer 39

Speeds up reaction by lowering activation energy. Not consumed in the reaction. Types of Catalysts: Heterogeneous – Different physical state than reactants. Homogeneous – Same physical state as reactants. Chemical Kinetics: Affects the fraction of effective collisions.

Question 40

What is the Rate Law?

Answer 40

Describes the quantitative relationship between reaction rate & reactant concentration. Shows how reaction rate depends on initial concentrations.

Question 41

What is a Reaction Mechanism?

Answer 41

Most reactions do not occur in a single step. Reaction mechanism = a series of steps that make up the overall reaction.

Question 42

Types of Collisions:

Answer 42

Unimolecular – 1 reactant molecule. Bimolecular – 2 reactant molecules. Termolecular – 3 reactant molecules (rare)

Question 43

Reaction Intermediates

Answer 43

Molecules formed in one step & consumed in another. Do NOT appear in the overall reaction (cancel out).

Question 44

Rate-Determining Step (RDS)

Answer 44

The slowest step in the mechanism. Controls the overall reaction rate (like a bottleneck in traffic).