All About Phases

Today in chemistry class we started out by learning about phase diagrams. They are representations of the state of substances based on the temperature and pressure conditions. The pressure is listed on the y-axis( in mmHg) and the temperature on the x-axis (in degrees celsius). The points on the graph indicate that states are in equilibrium. Point A, the triple point, is a point where all three states are in equilibrium. If a substance is gotten to exactly the right temperature and pressure of its triple point, all three states will be present.

We learned that the state of a substance can be manipulated by using pressure. For example, a tank of propane gas used for grilling is kept at high pressure in order for it to remain in liquid state in the tank before it is needed. However, when the valve is open to get the propane gas to the grill, the pressure is lessened and the propane needed is changed to gas form.

Mr. Lieberman did a demo where he simulated boiling by putting dry ice in a beaker of water. He said that once the pressure in the gas bubbles equals the pressure in the water, vapor will be formed.

Mr. Lieberman also did a demo that proved that pressure affects the state of water and any other pure substance. He put a beaker of water inside a vacuum and started lowering the pressure. The water started boiling within 30 seconds and produced vapor.

Lastly, Mr. Lieberman showed us dry ice in all three states by putting some in a tube and sealing all the holes. He then held this tube into a beaker of water and we watched the dry ice turn into liquid form from its solid state. Also, we saw vapor bubbles frequently during many attempts at perfecting this demo. These vapor bubbles indicated the presence of a hole in the seal of the tube. Finally we saw dry ice in liquid form!

This has been Korri H!!

The next scribe is Katie I.

Don't forget to do the worksheet!