Unit 1 Thermochemistry Chem 30

Energy is the ability to do work. It’s common form is heat.

from the sun.

Stored energy, otherwise known as potential energy is the energy of an object due to its position. For example, a bow spring has more potential energy when compressed or stretched rather than when it’s relaxed. Another example is, a steel ball has more potential energy when its raised above the ground than it has after falling to ground.

The lasting attractions between atoms, ions or molecules.

Term given to buried combustible geological deposits of organic material. Formed from decayed animals and plants converted into crude oil, coals, natural gas and heavy oils by exposure to heat and pressure of the earth’s crust over hundreds of million of years ago.

• - Energy cannot be created or destroyed 
• - energy can change form through physical or chemical processes
• - If chemical system (/mixtures) gain energy the surrounding loses energy
• - If chemical system (/mixture) loses the surrounding gains energy.

Mechanical means produced by machines or machinery (basically anything that can do work)

• Mechanical energy is the sum of potential and Kinetic energy.
• Kinetic energy - energy due to motion 
• Potential energy - stored energy by position. For example a spring has more potential energy when it’s compressed or stretched than when it is relaxed. Another example is, a steel ball has more potential energy when it’s raised above the ground than it has when falling to ground.

• - electrical energy
• - light energy
• - heat energy

Any chemical compound composed of only the elements Carbon and hydrogen.

The combustion of hydrocarbon in a bomb calorimeter or closed system, water is liquid state. The combustion of hydrocarbon in open system, water is vapour state.

A chemical reaction that is accompanied by the absorption of heat from its surrounding, heat enters the chemical system(/mixture), cooling of its surrounding. Resulting in an increase of chemical potential energy.

A chemical reaction accompanied by the release of heat to its surrounding, heat leaves the chemical system(/mixture), heating up its surrounding. Resulting in a deacrease of chemical potential energy.

The substances that goes into a chemical reaction

The substances produced at the end of the chemical reaction

• The reason is due to how much energy is required for bond breakage and how much energy is released by bond formation. 
• endothermic - more energy is consumed for bond breakage than released by bond formation.
• Exothermic - more energy is released by bond formation that what is consumed for bonds breakage

Stored energy.

• The process by which plants use water, sunlight and carbon dioxide to produce oxygen and energy in the form of sugar. 
• photosynthesis is endothermic

Glucose is used by plants as food

It’s when plants breaks down sugar/glucose in the presence of oxygen to produce ATP

Adenosine triphosphate is a form of stored energy that cells use to carry out essential processes.

6CO2(g) + 6H2O(l) + sunlight = C6H12O6(s) + 6O2(g)

C6H12O6(s) + 6O2(g) = 6CO2(g) + 6H2O(l) + ATP

The study of the the flow of energy in chemical reactions

Stored energy of an object due to its position. It also means the energy stored in the bonds of a substance (/between substance) and relative intermolecular forces.

Intermolecular forces are the forces of attractions or repulsion between neighbouring particles (atom, molecules or ions.)

Relating to heat

Is the total kinetic energy of all particles of a system. Thermal energy increases with temperature.

It states that particles are always in constant random motion; this motion is directly related to temperature.

particle motion increases, temperature increases. Particle motion decrease, temperature decreases

If energy increases, heat increases and will result to the increase of temperature.

The heat (energy (J)) required to raise the temperature of a unit mass (one gram (g)) of a substance by one degree Celsius;

The iceberg, because thermal energy is related to the amount of something you have multiplied by temperature. Even if an iceberg is colder = less energy or temperature it’s size however as a whole is thousand times larger than a cup of coffee.  Collectively An iceberg has more moving particles = more energy.

The higher amount the of heat is required to raise the temperature.

Q=mcΔt 

• Q= the change in thermal energy/kinetic energy (Joules (J))
• m= Mass (grams (g))
• Δt= change in temperature (celsius (°C))

• The total potential energy within a chemical system. the total potential energy of a system under constant temperature and pressure.
• Enthalpy is the energy possessed by the system

• ΔrH
• Δ - Change in ….
• r or x - is any chemical reactions 
• H - enthalpy

• this formula could
• ΔcH (c for combustion)
• ΔfH (f is for formation)
• ΔdH (d is for decomposition)

• Open system - matter and energy can flow in or out or be exchanged
• Closed system - matter cannot be exchange but the exchange of energy is possible 
• Isolated System - matter and energy cannot be exchanged

• Molar Enthalpy is the change in Enthalpy expressed per mole of a substance under a specific reaction.
• units are (kJ/mol) 
• equation of Molar Enthalpy is ΔrHm 
• equation to determine Molar Enthalpy is ΔrH = nΔrHm

• They are the same but have reversed signs (positive +, negative -)
• At the end of Molar Enthalpies we need to make sure that we have the correct sign (+ or -)

n=m/M

• The process of measuring the amount of heat released or absorbed in a chemical reaction. 
• We use calorimetry to determine if a chemical reaction is endothermic or Exothermic.

The measure of the average kinetic energy of particles in a system.

The transfer of thermal energy. Heat is not possessed by a system, heat is the energy flowing between systems.

• Molecule is a unit used to talk about atoms, molecules or compounds. 
• it is the amount of a substance that contains exactly 6.02214076 x 10^(23) of that substance (it means that you have that much of that thing)

It means how well a device can convert one mole of energy into another. 

• Formula: 
• Efficiency = output energy/input energy x 100%
• Efficiency = Q/ΔrH° x 100%
• Efficiency = mcΔt/nΔrH°m x 100%

• 1) By stating the Molar Enthalpy of a specific reactant in a reaction.
• 2) By stating the Enthalpy change for a balance reaction equation
• 3) By including an energy value as a term in a balance reaction equation. 
• 4) By drawing a chemical potential energy diagram.

• Stating the molar Enthalpy of a specific reactant in a reaction. 
• Eg: ΔcHm° = -725.9KJ/mol
•       CH3OH

• Stating the Enthalpy change of a balanced reaction equation
• How to calculate for Enthalpy changes steps
• 1) Start with a balanced reaction equation
• 2) Determine the chemical amount (/mole) of the asked substance
• 3) Use ΔrH° =nΔrHm° to determine the Enthalpy change for the whole reaction
• 4) Then report the Enthalpy change by writing it next to the balanced reaction equation.

By including the energy value as a term in the balance reaction equation.

If a reaction is endothermic (+), it requires additional energy to react, so it is listed with the reactants

If a reaction is exothermic (-), energy is released as the reaction proceeds, so it is listed with the products.

Drawing the chemical potential energy diagram

• The diagrams 3 labels are
• - the title (Eg “the formation of ___” or “The decomposition of ___”)
• - y axis is labeled as “Ep” (potential energy)
• - x axis is labeled as “Reaction progress”

The potential energy change of the reaction in a calorimeter will equal the kinetic energy change of the water therefore Ep=Ek