Rachel Battaglia
The Motion of Molecules: The Kinetic
Molecular Theory (Unit Goals)
1. STATE OBJECTIVES
C2.2 Molecules in Motion
C2.2A Describe conduction in terms of molecules bumping into each other to transfer
energy. Explain why there is better conduction in solids and liquids than gases.
C2.2B Describe the various states of matter in terms of the motion and arrangement of
the molecules (atoms) making up the substance
C2.2x Molecular Entropy
C2.2c Explain changes in pressure, volume, and temperature for gases using the kinetic
molecular model.
C2.2d Explain convection and the difference in transfer of thermal energy for solids,
liquids, and gases using evidence that molecules are in constant motion.
C2.2e Compare the entropy of solids, liquids, and gases.
C2.2f Compare the average kinetic energy of the molecules in a metal object and a wood
object at room temperature.
C2.3x Breaking Chemical Bonds
C2.3a Explain how the rate of a given chemical reaction is dependent on the temperature
and the activation energy.
C2.3b Draw and analyze a diagram to show the activation energy for an exothermic
reaction that is very slow at room temperature.
2. & 4. BIG IDEAS & EXAMPLES (3. Is next section)
C2.2 Molecules in Motion
C2.2A Describe conduction in terms of molecules bumping into each other to transfer
energy. Explain why there is better conduction in solids and liquids than gases.
C2.2B Describe the various states of matter in terms of the motion and arrangement of
the molecules (atoms) making up the substance.
Big Idea - Molecules that make up solids, liquids and gases each have different speeds.
Gases have the fastest moving molecules. Solids have the slowest moving molecules and
liquids are in the middle. Solid objects have atoms that are always in contact with other
molecules. The more space between the atoms the lower the conduction. Since conduction
is the transfer of heat from one object to another, when molecules are further away they
cannot transfer heat as easily to each other since they are not in constant contact like
solids. This is why liquids and gases have a harder time conducting and solids have an
easier time conducting heat.
Examples: The 3 basic assumptions of the Kinetic Molecular Theory
Mole, Moles, Molarity, Molality, Adogadro’s number –Students will learn the definitions
and do calculations based on them.
Atom
C2.2x Molecular Entropy
C2.2c Explain changes in pressure, volume, and temperature for gases using the kinetic
molecular model.
Big Idea - Pressure is the amount of force that impacts the walls of a container, room or
area. A change in pressure results from a volume change. Volume is the area of space
that a solid, liquid or gas takes up. A change in volume results from a change in pressure
and temperature. Temperature is the amount of internal kinetic energy.
Examples:
Le Chatelier’s principle in relation to Kinetic Theory: change in concentration, pressure,
temperature.
Boyle Law, Charles Law and their laws making up the IDEAL GAS LAW
Students will do their own lab based on the ideal gas law. They will take measurements
like Charles did.
Stochiometry
C2.2d Explain convection and the difference in transfer of thermal energy for solids,
liquids, and gases using evidence that molecules are in constant motion.
C2.2e Compare the entropy of solids, liquids, and gases.
Big Idea – Convection is the transfer of energy from an object to its environment, due to
pressure that it create from hitting the walls of its space. Since different matter has
different molecular speeds, faster moving molecules create more energy thus creating
more heat. The faster the molecules move the higher the entropy. Entropy is the disorder
that molecules have. The higher the entropy the more heat that is created. Since gas
molecules have more speed than liquid and solid molecules they have more heat. When
liquids and gases get hotter their densities decrease, making the entropy move to the area
where there is less heat. This creates more heat.
Examples: Thermal Expansion
Thermodynamics - Delta G = Delta H – T* DeltaS
Phase Change experiments – using ICE calculations to find moles
Boltzmann’s constant is the in pV= nRT is pV=nKT
pV= nRT
C2.2f Compare the average kinetic energy of the molecules in a metal object and a wood
object at room temperature.
Examples: Graham’s Law – rate of effusion = Rate 1/ Rate2 = sqrt(M1/M2)
Rate= Speed of pdts/speed of reactants or [pdts]/ [reactants]
C2.3x Breaking Chemical Bonds
C2.3a Explain how the rate of a given chemical reaction is dependent on the temperature
and the activation energy.
C2.3b Draw and analyze a diagram to show the activation energy for an exothermic
reaction that is very slow at room temperature.
Big Idea - The higher the temperature the faster the molecules are converting to a new
substance, reducing the rate of a reaction.
Examples: Looking at graphs and being able to read the graphs by knowing the
characteristics of the graphs.
Changes in enthalpy equations –problems to work on
Delta G = Delta H – T* Delta S
Gibbs Free Energy
Kinetics- v= -Delta [A]/Delta T = k* A
3. Summary of Big Ideas.
Molecules are made of atoms. Every molecule has a specific molar mass. The
molar mass of a substance is the measurement of one mole of a substance. A mole is a
unit of measure for an amount of a substance. One mole is equivalent to Avogadro’s
number, 6.022 * 10 ^23. This is the number of entities in a mole. Moles can be calculated
by taking the molar mass of a substance and dividing it by the grams of that substance.
Moles are used in most chemistry calculations and are the basis for finding mathematical
outcomes that translate into scientific evidence to create a rule, theory or fact. Once
moles are understood we can use them to calculate molarity and molality. Molarity is a
way to find the concentration of a solution by taking the moles of a solute and diving it by
the liters of a solution. Molality is another way to calculate the concentration of solution.
Molality is calculated by diving the moles of a solute by the molecular weight of the
solute.
The Kinetic Molecular theory states,
“gases consist of large numbers of molecules that are in continuous, random
motion. The volume of all the molecules of the gas is negligible compared to the
total volume in which the gas is contained and the attractive forces between gas
molecules are negligible” (Rudolf Clausis, Kinetic Molecular Theory).
Gas molecules move faster than liquid and solid molecules. Solid molecules just barley
move. The faster the moving molecules the more heat that is produced. Heat transfers
from areas of greater heat to areas of lesser heat through conduction and convection.
This happens because systems want to be in equilibrium with each other. When heat
transfers in chemical reactions it helps the reaction reach equilibrium faster. This can
happen because of different state and property changes. The states and property changes
can occur through changes in heat, pressure, temperature, volume and concentration.
Through the Ideal Gas law’s equation we can plug in the previous characteristics in
numerical form to find the missing piece of information. Through that we can classify the
changes that occurred.
Works Cited
"Kinetic-Molecular Theory." The Innovative Teaching Laboratory. Web. 20 Mar. 2011.
<http://itl.chem.ufl.edu/2041_u00/lectures/lec_d.html>.