Macroscopic

Observations

Micromodels

By: Jerry Gentry

TOPIC: THREE CRYSTALS10/O8/09

IceMacroscopic ObservationsClearColdSolidIt melted as we watchedNo smell

http://www.worldofmolecules.com/interactive_molecules/ice.htm

Micromodels

Click on the link to go to an interactive ice molecule. Right below on the same linked page there is also an interactive liquid water molecule. The red balls are oxygen(O) and the white ones are hydrogen(H). Water/ice has polar covalent bonds. Each water molecule is connected to another one through Hydrogen bonds. Notice that the ice molecules are spaced out further than the water. That is why ice is less dense and floats in water.

These molecules were created with the Jmol App and are a part of the “World of Molecules” website which can be found with this link.

IodineMacroscopic Observations

Turned the paper yellowShiny-has lusterThe yellow went through the paperRoom temperatureTurned blue in the water/ice

Micromodels

http://www.creative-chemistry.org.uk/molecules/structures.htm

http://image.tutorvista.com/content/matter-surroundings/subliimation-at-submicroscopic-level.jpeg

This link goes to an interactive molecule of iodine. The purple is iodine molecules. They have nonpolar covalent bonds.

This link shows iodine in the process of sublimating. Sublimation is when the iodine goes from a solid straight to a gas. This occurred when the iodine gave off a yellow color that appeared on and through the paper.

This linked model was creqted with Chem Axon Ltd for the “Creative Chemistry” website. ©2000-2009

This linked model is part of the “Tutor Vista” website. ©2008

http://www.worldofmolecules.com/interactive_molecules/salt.htm

Macroscopic ObservationsTastes saltyVery hardClearRoom temperatureMelted the ice when it came into contactDoesn’t react with iodine

Micromodels

Click on the link below to view an interactive salt molecule. The purple is sodium(Na) and the green is chlorine(Cl). Salt has ionic bonds. A salt molecule can’t have hydrogen bonds because it doesn’t contain Oxygen, Nitrogen, or Fluorine.

This molecule was created with the Jmol App and is part of the “World of Molecules” website. ©1999

Questions/Comments/Conclusions

•How does Iodine turn the paper yellow?•Why does Iodine turn blue with water?

•How does salt melt ice?

Static Electricity10/09/09

Macroscopic Observations

Static electricity pulled the water toward itselfThe balloon had to be pretty close before it attracted the water

http://www.csiro.au/helix/sciencemail/activities/images/WaterBendMolecules.gif

MicromodelsClick on the link below to go to a picture that shows why the balloon pulled the water toward itself. You will see a negatively charged balloon(when you rubbed the balloon on your hair you gave the balloon electrons or static electricity. This attracts the positive ends of the water molecules and makes them align. The positive parts of the water molecules are hydrogen and the negative is oxygen. This is a good example of intermolecular forces. One thing it doesn’t show is that before the water molecules get close to the balloon they aren’t aligned.

This model is part of the “Science by Email” website

EthanolMacroscopic Observations

Static electricity pulled ethanol toward itselfHad a slightly stronger reaction than waterSmelled like gas

MicromodelsThis is a model of static electricity attracting ethanol. The balloon shown is negatively charged after being rubbed on someone’s hair. The nonpolar ethanol has a positve end so it is attracted to its opposite. This makes the molecules align with the balloon and change the water current. The red is oxygen, the greens are carbon, and the others are hydrogen for the ethanol.

The ethanol molecules are from “The Interactive Library” at Edinformatics.com and the balloon is from the “Science by Email” website.

HEXANEMacroscopic Observations

No reactionSplashes on the counter evaporated quickly

Micromodels

This model shows that hexane does not react to the negatively charged balloon. Hexane is nonpolar so it doesn’t have opposite ends(positive and negative). This means that nothing will be attracted to the balloons electrons and so the hexane won’t align with them. Since nothing attracts, the flow of hexane doesn’t change.

The hexane molecules were created by Ben Millis and were found on “Wikimedia Commons.”The balloon was found on “Science by Email.”

Questions/Comments/Conclusions

What is being aligned?Why doesn’t some

water/ethanol get pushed away from the balloon even

though there is also a negative side to the

molecule?

Topic:10/13/09

Ethyl AlcoholMacroscopic ObservationsEvaporated pretty quickly on glassEvaporated slowly on plastic2 drops for the microspatulaEasy to pull glass apartEasy to pull plastic apart

Plastic Glass

MicromodelsEthyl alcohol evaporates a little slower than acetone but faster than water. Ethyl alcohol can cohere and adhere much better than acetone but not as well as water. Hydrogen bonds form between hydrogen and oxygen on the glass so that adheres. Ethyl alcohol has oxygen in it so that makes it able to cohere but because of its structure it doesn’t have as strong of a cohesion as water. Since it doesn’t hold itself together as well it separates and then evaporates. The black lines are bonds and the red is oxygen.

WaterMacroscopic ObservationsDidn’t evaporate while we watched2mm height on glass10mm width on glass2.5mm height on plastic5mm width on plastic3 drops for microspatulaEasy to pull apart on plasticKind of hard to pull apart glass

Plastic Glass

Micromodels

These models show why water didn’t evaporate as fast as the other two did. The green lines within the water droplet are hydrogen bonds that hold water molecules together. That is called cohesion. Water also forms a bond with the plastic which is called adhesion. The hydrogen in the water forms a hydrogen bond with the oxygen in the glass. Since everything is bonded together it takes a lot longer to break them apart and for the water to evaporate. The black lines are also hydrogen bonds. The red on the glass is oxygen.

GlassPlastic

AcetoneMacroscopic Observations

oEvaporated the quickest of the threeoEvaporated a little quicker on plastic than on glasso2 drops for the microspatulaoHard to pull glass apartoEasy to pull plastic apart

Plastic Glass

MicromodelsAcetone evaporates quickly because it can’t cohere. It can adhere to other things with hydrogen bonds but since it doesn’t bond with itself it can’t hold itself together and avoid evaporation. The hydrogen in acetone can form a hydrogen bond with the oxygen in glass but there is nothing for it to bond with in plastic. This makes it evaporate faster on plastic. The black lines are hydrogen bonds between the white hydrogen and the red oxygen. The green is carbon and the red in acetone is oxygen.

Plastic

Questions/Comments/Conclusions

Why does acetone evaporate so quickly?Why can’t acetone cohere?

Why did the alcohol evaporate almost as quickly as the acetone if it bonds a lot better?

Topic: Boiling Water10/15/09

Macroscopic ObservationsLittle bubbles form on the bottom and then break off and riseBubbles stop at surface for a little bit before breaking throughMore steam appears when there are more bubblesSome bubbles rise straight up and others zigzagAfter awhile bubbles start to appear on the side tooSome bubbles got halfway through surface but got stuck for awhile

Micromodels

This is a model created by Charles E. Ophardt from Elmhurst College for the college’s online “Virtual ChemBook.”©2003

This model shows the boiling of water. When heat or energy is applied to the bottom it starts to make the molecules move. More and more start to move from the bottom up until it is boiling. The bubbles are just pockets of water vapor that formed after molecules split far enough apart from each other. Since they are less dense they rise to the surface and then break through.

Purple=oxygenWhite=hydrogen

Nucleation Site (The Penny)Macroscopic Observations

Bubbles came mainly from the pennyPenny shook a lotIt created a nucleation siteBubbles were larger than before

Micromodels

This is a model of what happened when we dropped the penny into the boiling water. It created a nucleation site in the beaker which allowed many bubbles to form on the penny. A nucleation site is just an area with many holes or rough spots that bubbles can form in. Since there are so many rough spots on a penny there were a lot of bubbles forming there.

Red/purple=oxygen white=hydrogen

Questions/Comments/Conclusions

Why do some bubbles go straight up and others zigzag?Why did some bubbles get stuck at the surface for awhile and others went through quickly?Why did some bubbles form on the side instead of the bottom later on?

The End