## Richard A. Paselk

Science 331
Fall 2004 Lecture/Activity Office: SA560a
Notes: 30 August Phone: x 5719
Home: 822-1116
e-mail: rap1

# Energy

Law of Conservation of Energy: Energy is neither created nor destroyed in chemical processes. The problem here of course is - What is energy? Energy is the capacity to do work. So what's work? Work occurs when an object (mass) is moved against a force. Some common forms of energy important to our study include:

• Kinetic Energy (KE) - energy due to motion. KE = 1/2 mv2.
• Potential Energy (PE) - energy due to position.

Another form of energy we need to be familiar with is:

• Heat - energy transferred between objects because of a difference in temperature.
• Heat vs. Temperature: heat tells us how much energy is held (can be transferred from) and object or given mass of stuff. Temperature on the other hand is a measure of the energy per particle in a sample of matter. Thus for a gas temperature is a measure of the average Kinetic Energy (KE) of the gas particles, while the amount of energy we must add to the gas to achieve this average KE is the heat.
• Note that most energy eventually ends up as heat (ex.: burning gasoline to move a car - heat in exhaust, friction in tire deformation, braking, etc.) or work (car is moved against its inertia).

Note that these forms of energy are readily interconverted.

# Matter

Last time we looked at some gerneral properties of matter, and explored the physical states of the non-radioactive elements. Let's look at matter in a variety of forms and try to deduce some thing about its make-up. Recall the states of matter.

## States of Matter and Changes of State

Matter can exist in three states under earth-surface conditions:

• Solid: definite shape and volume (Crystals vs. super-cooled liquids or glasses)
• Liquid: definite volume, but no defined shape - will fit to container etc.
• Gas: no definite shape or volume - will fill whatever container they are in.

A common form of matter exhibiting these states under lab conditions is water. Let's look at water starting in its solid state and observe its transitions. We'll use the following equipment:

• Heat source (bunsen burner)
• Beaker
• Thermometer
• Test tube
• Scale
• Ice

So let's all melt some ice and observe what happens:

• Fill beaker with ice, measure temperature and weight
• Melt partially, measure temperature.
• Continue measuring temperature as ice is heated and melts.
• When ice completely melted, weigh again.
• Note temperature change as liquid water is heated.
• Note temperature as water boils.
• Hold a test tube containing ice above boiling water, NOT in steam, and observe what happens.

What can you say about what has happened? e.g.:

• Do you think mass was conserved?
• Was the water changed?
• Is ice a true crystalline solid? Why or why not?

## Matter and Atoms

Why do we think atoms exist?

• Crystals.
• Gases.

Demo spectroscopes and gratings - rainbows vs. line spectra.