space.template.3+Lab4.Dissolved+Oxygen+Levels

=The Magic of Mentos=

Objective: Identify the effects of temperature on the solubility of gasses and observe how polar molecules interact.

As noted in previous lab activities, temperature effects the rate of solubility of substances in various ways. The solubility ionic and molecular solids that you dissolved in the water increased as the temperature decreased; meaning that more solute could be dissolved at higher temperatures. But is the same true for gasses?

Gasses tend to be less soluble with increasing temperature. This is due to the fact that as the temperature increases, the kinetic energy of the molecules increase. This causes the gas molecules to escape from the liquid faster than they would if the temperature was lower and the kinetic energy of the molecules was less.

How then would an increase in temperature affect fish living in your local pond? Fish tend to be cold blood animals, meaning that their body temperature changes with the environment around them. As the water temperature increases, the fish require more oxygen to keep up with the demand of their faster metabolism. As the water temperature increases, the oxygen levels decrease. This causes the fish to have a depletion of oxygen and possibly die off, resulting in fish kills.

Liquids may be pressurized to contain more gasses than their saturation points will allow. Take soda for instance. The bubbles that you see in the soda are pockets of carbon dioxide just waiting to escape. The carbon dioxide was pumped into the liquid right before it was sealed, forcing the liquid to become overly saturated with the gas. So why is it that the carbon dioxide doesn't escape when you open the bottle?

Water as you learned from the previous lab, is a polar molecule. Polar molecules tend to have a positively charged and a negatively charged end. The molecules tend to stick together based on their charges. This creates surface tension. The carbon dioxide that is pumped into soda is trapped in the liquid because of the surface tension, created by the water molecules that are contained within it, seals it in. What might happen if this surface tension is broken. Will the carbon dioxide atoms join together and escape? Or will they be forever trapped in the liquid?

Prelab 1.) How does temperature effect the rate of solubility of gasses? 2.) What possible effect would an increase in temperature have on fish in a local pond? 3.) Why does soda explode when it is shaken? 4.) What type of molecule is water? 5.) Predict what will happen when mentos are dropped into soda and explain why this occurs.

Procedure You will be given a pack of mentos and a bottle of soda. Describe what you will

Data Describe what happened when the mentos was dropped in the water.

Analysis 1.) What caused the soda to react like it did? 2.) What else could you do to the soda to have the same effect? 3.) What happens to the soda when it becomes flat? 4.) Why does decrease the temperature of a liquid, increase the amount of gas that can be dissolved in it? 5.) Why do polar molecules tend to stick together.

Conclusion Was your hypothesis correct? What other materials besides mentos might make this experiment work. Would you change anything in your experiment.