The Role Of Kinetic Energy In Physical

Changes

By:Michael Lau

Jasmine Li

Canita Mai

OverviewIn order to understand the role of kinetic energy in physical

changes, a basic understanding of the 3 different types of kinetic energy that molecules possess is required.

The 3 Subsections Of Our Presentation

•The 3 Types of Kinetic Energy

•Practical Applications of Kinetic Energy Changes

•How Kinetic Energy Changes Phases

The 3 Types of Kinetic Energy

As we already know, all molecules are in constant motion. In this first subsection,

we will explore how kinetic energy makes molecules move.

The 3 Types of Kinetic Energy

1. Rotational Energy

• Symbol: EROT

• How it makes molecules move:

This type of kinetic energy makes molecules rotate around an axis, however, the bond between the atoms do not change

• Examples:

Hey! I am a water molecule, and I will be showing you how these different types of kinetic energy affect me!

The 3 Types of Kinetic Energy

2. Vibrational Energy• Symbol: EVIB

• How it makes molecules move:This type of kinetic energy changes the bond lengths and

angles between the atoms• Examples:

There are several ways this kinetic energy affects the bond lengths! But remember, this kinetic energy changes the relative movement of the atoms of a molecule.

1. 2.3.

The 3 Types of Kinetic Energy

3. Translational Energy

• Symbol: ETRANS

• How it makes molecules move:

This kinetic energy causes molecules to travel in a straight line from one location to another. However, this kinetic energy does not affect the bond length or angle.

• Examples:I will move in a straight line, until I pump into an obstacle, in that case, I will travel in the opposite direction.

Practical Applications of Kinetic Energy Of Molecules

The two common applications of vibrational kinetic energy in molecules are described below:

Microwave Ovens:

How it works: The microwave supplies water molecules in the food the kinetic energy it needs to vibrate back and forth. The molecules absorb the heat and thus its bonds are able to stretch back and forth. (see diagram on EVIB)

What this does: This application of kinetic energy in molecules allow food to be heated in a relatively shorter time.

Practical Applications of Kinetic Energy Of Molecules

Infrared Spectroscopy:

How it works: An unknown molecule is put under the exposure of IR energy, which is simply a type of heat energy. Because different molecules have different bonds, the molecules will vibrate in different ways, with the supply of heat energy.

What this does:This application allows for the identification of different types of molecules.

The Role Of Kinetic Energy In Phase Changes

The phase changes of, in this case, water, are greatly assisted by the kinetic energy of each H2O molecule when heat is added.

The Role Of Kinetic Energy In Phase Changes

Phases: Types of Kinetic Energy:

EROT EVIB ETRANS

Solid Not involved. Both vibrational and transitional energy cause the molecules to oscillate and bump into each other. At a certain point, the molecules will break free form its neighbors.

Melting Not involved. The level of transitional energy reaches its maximum point, allowing the solid to break its form and melt.

Liquid In this phase, all three types of kinetic energy are at play, allowing molecules to move at an increasingly fast speed.

Boiling Again, transitional energy reaches maximum point, allowing the liquid to start evaporate into gas.

Gas During this phase, all three kinetic energies are at play. Any addition of heat will only make gas molecules move faster.

Thank you for listening, and we hope you learned something new!

Bibliography

*Please note: all diagrams were done by computer, they were not from internet.

Text Source:

Hebden, James A. Hebden: Chemistry 11, A Workbook for Students. Kamloops, BC: 1998.

Picture Sources:

http://cirellio.files.wordpress.com/2008/06/boiling-water.jpg

http://carol.gimp.org/writing/images/Ice_cubes_openphoto.png

http://www.dailygalaxy.com/photos/uncategorized/2007/10/03/magic_gamma_rays.jpg

http://www.appliancist.com/ge-cafe-over-the-range-microwave-oven.jpg

http://das.okstate.edu/EXCEL/This%20Water%20Drop.jpg

http://www.moorewallpaper.com/Water-11.jpg

http://www.acclaimimages.com/_gallery/_pages/0093-0509-2111-5314.html