✨ ap chem survival packs are ready!

ap chem study guides

🌀  Unit 3 - Intermolecular Forces and Properties

👟  Unit 5 - Kinetics

🔥  Unit 6 - Thermodynamics

⚖️  Unit 7 - Equilibrium

  Unit 9 - Applications of Thermodynamics

🤺  AP Chemistry Essentials

6.3 Kinetic Energy, Heat Transfer, and Thermal Equilibrium

#kineticenergy

#thermalequilibrium

⏱️  2 min read

written by

anika p

Dalia Savy

dalia savy

Dylan Black

dylan black

(editor)

August 22, 2020


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: 

  1. The rate of a reaction is proportional to the rate of the collisions 💨

  2. Orientation matters for the reactant molecules colliding ➡️⬇️

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2FCNX_Chem_12_05_COandO2.jpg?alt=media&token=d2435ac4-4b37-4ad9-9861-bc37c1e866d8

Image Courtesy of Chemistry BC Textbook

Successful collisions would therefore collide with proper orientation to break bonds and have enough energy to overcome the reaction’s activation energy.

Just remember, proper orientation + enough energy = successful collision.

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.

Basically, the heat goes from the source (hot item) to the sink (cold item), until thermal equilibrium is reached. At thermal equilibrium, molecules are moving at the same speed since the temperatures are the same.
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Fu18l1e5.gif?alt=media&token=818e1627-ea0a-4e36-8fc5-1ee9290a1e45

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.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Fthermo0.gif?alt=media&token=1fa2b4d9-5551-4606-b0d0-e7312d7f2b3c

Image Courtesy of NASA

continue learning

Slide 1 of 11
Fiveable

Join Our Community

Fiveable Community students are already meeting new friends, starting study groups, and sharing tons of opportunities for other high schoolers. Soon the Fiveable Community will be on a totally new platform where you can share, save, and organize your learning links and lead study groups among other students!🎉

Fiveable Logo

2550 north lake drive
suite 2
milwaukee, wi 53211

92% of Fiveable students earned a 3 or higher on their 2020 AP Exams.

*ap® and advanced placement® are registered trademarks of the college board, which was not involved in the production of, and does not endorse, this product.

© fiveable 2020 | all rights reserved.