6.3 Kinetic Energy, Heat Transfer, and Thermal Equilibrium
3 min read•january 29, 2023
Anika P
Dalia Savy
Anika P
Dalia Savy
Molecular Collisions
Temperature reflects the average kinetic energy, or random motion, of particles. Kinetic energy is speed, so as temperature increases, molecules collide with the walls of the container faster.
The Collision Theory
Collision theory is based on the following postulates:
The rate of a reaction is proportional to the rate of the collisions 💨
Orientation matters for the reactant molecules colliding ➡️⬇️
Image Courtesy of Chemistry BC Textbook
To understand how collision theory works, it's useful to think of an analogy to break down the molecular processes. Let's say you're making lemonade. To make lemonade, you need to mix lemon juice, sugar, and water together. But just having the ingredients in the same place isn't enough to make lemonade - they need to interact with each other in just the right way.
Collision theory is like the "rules" for how ingredients can mix together to make a reaction happen. It says that for two things to react and form a new substance, they need to bump into each other with enough energy, in the right orientation, and often enough. Think of it like two billiard balls - if they don't hit each other hard enough, or at just the right angle, they won't react.
And just like how making lemonade faster would require you to mix the ingredients more quickly, the theory also explains how increasing the temperature or concentration of reactants can make the reaction happen faster by increasing the number and energy of collisions.
Successful collisions would therefore collide with proper orientation to break bonds and have enough energy to overcome the reaction’s activation energy.
If we look at this in terms of heat transfer, higher temperatures mean a higher number of collisions because the reactants are moving quickly. Heat conduction involves this high temperature state going to a low temperature state, where collisions are not as frequent due to the decrease in temperature.
Transfer of Heat Between Objects
As we see in real life, heat travels from a hot object to a cold object until the two are in thermodynamic equilibrium (thermal equilibrium). Take for example, putting a pan🍳 up against hot grates on a stove that are heated up by a fire. The heat travels from the grates to the pan until the two are the same temperature.
Image Courtesy of ThePhysicsClassroom
The Zeroth Law of Thermodynamics
The Zeroth Law of Thermodynamics is stated as "if a is in thermal equil. with b and b is in thermal equil. with c, then a is in thermal equilibrium with c" where a, b, and c are bodies.
Image Courtesy of NASA
Key Terms to Review (12)
Activation Energy
: Activation Energy is defined as the minimum amount of energy required to initiate or start up a chemical reaction.Collision Theory
: Collision theory explains how chemical reactions occur and why reaction rates differ for different reactions. The theory states that for a reaction to occur, particles must collide with sufficient energy (activation energy) and correct geometric orientation.Heat Conduction
: Heat conduction is the process where heat flows within an object or between objects due to their physical contact and difference in temperature.Heat Transfer
: Heat transfer refers to the movement of thermal energy from one object or place to another because of differences in temperature.Kinetic Energy
: Kinetic energy is the energy possessed by an object due to its motion.Molecular Collisions
: Molecular collisions refer to the interactions between molecules that can result in a chemical reaction or a physical change.Reactant Molecules
: Reactant molecules are the substances that start a chemical reaction. They interact with each other to form new products.Successful Collision
: A successful collision in chemistry refers to reactant molecules colliding with enough force and correct orientation so that they break old bonds and form new ones, leading to a chemical reaction.Temperature
: In chemistry, temperature measures the average kinetic energy of particles in an object or system. It indicates how hot or cold something is.Thermal Equilibrium
: A state reached when two objects connected by a path for heat transfer have equal temperatures and there's no net flow of thermal energy between them.Thermodynamic Equilibrium
: A state in a system where all the properties like temperature, pressure, and volume are uniform and do not change with time. It's when no net flow of matter or energy occurs within the system.Zeroth Law of Thermodynamics
: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.6.3 Kinetic Energy, Heat Transfer, and Thermal Equilibrium
3 min read•january 29, 2023
Anika P
Dalia Savy
Anika P
Dalia Savy
Molecular Collisions
Temperature reflects the average kinetic energy, or random motion, of particles. Kinetic energy is speed, so as temperature increases, molecules collide with the walls of the container faster.
The Collision Theory
Collision theory is based on the following postulates:
The rate of a reaction is proportional to the rate of the collisions 💨
Orientation matters for the reactant molecules colliding ➡️⬇️
Image Courtesy of Chemistry BC Textbook
To understand how collision theory works, it's useful to think of an analogy to break down the molecular processes. Let's say you're making lemonade. To make lemonade, you need to mix lemon juice, sugar, and water together. But just having the ingredients in the same place isn't enough to make lemonade - they need to interact with each other in just the right way.
Collision theory is like the "rules" for how ingredients can mix together to make a reaction happen. It says that for two things to react and form a new substance, they need to bump into each other with enough energy, in the right orientation, and often enough. Think of it like two billiard balls - if they don't hit each other hard enough, or at just the right angle, they won't react.
And just like how making lemonade faster would require you to mix the ingredients more quickly, the theory also explains how increasing the temperature or concentration of reactants can make the reaction happen faster by increasing the number and energy of collisions.
Successful collisions would therefore collide with proper orientation to break bonds and have enough energy to overcome the reaction’s activation energy.
If we look at this in terms of heat transfer, higher temperatures mean a higher number of collisions because the reactants are moving quickly. Heat conduction involves this high temperature state going to a low temperature state, where collisions are not as frequent due to the decrease in temperature.
Transfer of Heat Between Objects
As we see in real life, heat travels from a hot object to a cold object until the two are in thermodynamic equilibrium (thermal equilibrium). Take for example, putting a pan🍳 up against hot grates on a stove that are heated up by a fire. The heat travels from the grates to the pan until the two are the same temperature.
Image Courtesy of ThePhysicsClassroom
The Zeroth Law of Thermodynamics
The Zeroth Law of Thermodynamics is stated as "if a is in thermal equil. with b and b is in thermal equil. with c, then a is in thermal equilibrium with c" where a, b, and c are bodies.
Image Courtesy of NASA
Key Terms to Review (12)
Activation Energy
: Activation Energy is defined as the minimum amount of energy required to initiate or start up a chemical reaction.Collision Theory
: Collision theory explains how chemical reactions occur and why reaction rates differ for different reactions. The theory states that for a reaction to occur, particles must collide with sufficient energy (activation energy) and correct geometric orientation.Heat Conduction
: Heat conduction is the process where heat flows within an object or between objects due to their physical contact and difference in temperature.Heat Transfer
: Heat transfer refers to the movement of thermal energy from one object or place to another because of differences in temperature.Kinetic Energy
: Kinetic energy is the energy possessed by an object due to its motion.Molecular Collisions
: Molecular collisions refer to the interactions between molecules that can result in a chemical reaction or a physical change.Reactant Molecules
: Reactant molecules are the substances that start a chemical reaction. They interact with each other to form new products.Successful Collision
: A successful collision in chemistry refers to reactant molecules colliding with enough force and correct orientation so that they break old bonds and form new ones, leading to a chemical reaction.Temperature
: In chemistry, temperature measures the average kinetic energy of particles in an object or system. It indicates how hot or cold something is.Thermal Equilibrium
: A state reached when two objects connected by a path for heat transfer have equal temperatures and there's no net flow of thermal energy between them.Thermodynamic Equilibrium
: A state in a system where all the properties like temperature, pressure, and volume are uniform and do not change with time. It's when no net flow of matter or energy occurs within the system.Zeroth Law of Thermodynamics
: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
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