Tuesday, June 28, 2011

Activity 6: States of Matter and Intermolecular Forces

To begin this activity, review the Content Slides in D2L on States of Matter and Intermolecular Forces. We are all familiar with the states of matter (solids, liquids and gases) for many substances. In the First Activity we explored these states of matter for water. In Activity 6, we would like to take our overall understanding of states of matter to the molecular level. We will use the States of Matter simulation at http://phet.colorado.edu/ . There are two key characteristics of molecules that determine their state of matter. The first one is the temperature of the matter, and the second one is the intermolecular forces (how well atoms/molecules stick to one another) between atoms and molecules.

One of the first things to think about here is temperature. Temperature and thermometers have a very similar relation to speed and speedometers. For all practical purposes, a thermometer is really a speedometer for molecular speed or motion. At this site (another good NSF funded science education site) http://www.visionlearning.com/library/module_viewer.php?mid=48 , is a good overview of temperature with a good image of the temperature scales and conversions between different scales. Notice that the Kelvin scale starts at zero and goes up from there. This is like our car speedometer, in that at 0 Kelvin (K), molecular and atomic motions stop. As the temperature rises, atoms and molecules begin to move faster and faster.

The second thing to consider is the intermolecular forces (attractions) that exist between molecules. In the D2L content slides there are a few types of attractions described, notice all of these are defined by the attraction that exists between positive and negative charges. Water is a great example of a molecule that has strong attractions that we call hydrogen bonding. It is this strong attraction that makes water a unique molecule on our planet. It turns out that the hydrogen atoms tend to be positive in charge, and the oxygen atoms tends to be negative in charge.

Tasks to be completed for Acitivity 6

1. Convert 0°F, 32°F, 70°F, and 212°F to Kelvin

2. Complete the Teaching Idea: States of Matter Simulation Lab by Kelly Vaughan. Complete the lab worksheet as if you were a student, and then post this on your blog. You can scan it or just take a picture of it.

3. In the States of Matter simulation, choose the Solid, Liquid, and Gas Tab at the top of the screen. Choose the water molecule and cool the water to 0 K. Describe how the water molecules are aligned and attracted to each other. Which atoms are attracted to which other atoms?

4. Switch to the Phase Changes Tab on the States of Matter simulation. Notice how on the bottom right there is a small red dot that indicates where the system is at as far as temperature, pressure and state of matter. Play with the simulation to notice changes, notice that when you push down the pressure can go way up and explode the box. On your blog, report a temperature and pressure required to make oxygen a liquid. This is sometimes how the oxygen exists in pressurized oxygen tanks, perhaps like ones you may use to go diving.

5. List and describe at least two Science Standards that this activity addresses.

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