Evaporative Cooling
In the Evaporative Cooling lab, my partner and I tested the acetone by dropping small amounts onto the back of our hands and our palms. Our findings were that:
- the acetone got colder the longer it stayed on our hands until it eventually evaporated.
The cooling sensation we felt was due to the acetone vaporizing from a liquid into a gas. As the acetone evaporated, the liquid remaining on our hands cooled down because the molecules with the greatest kinetic energy turn to gas faster. Acetone is a product of nail polish, so this explains the cooling affect the occurs when it drys from fingers.
Polarity of Water Molecules
In the Polarity of Water Molecules lab, my partner and I tested the polarity of water in different aspects:
- when the drop of water was placed on the wax paper, it slides freely across it
- when two separate drops of water are placed on the paper and rolled towards each other, they combine into a bigger drop
- when soapy solution is added to the drop of water, the water seems to collapse on the paper
- when soapy solution is added to water on top of a penny, it causes the water to collapse/flow off of the penny.
There is no cohesion between water and wax, instead of the water molecules sticking to the wax they stick to the other water molecules, which causes the water droplets to merge when there is two seperate ones on the wax paper. The molecules form hydrogen bonds with eachother rather than trying to bond with the wax. When soap solution is put into the water it disrupts the formation of the hydrogen bonds because it is nonpolar while water is polar, the two can not bond so they stay seperate.
Surface Tension
In the Surface Tension lab, my partner and I tested the ability of surface tension on different materials (paper clips and sulfur):
- When the paper clip is slid onto the water it floats at the top
- Once a drop of soapy solution is added the paper clip drops to the bottom
- Sulfur floats on the surface when added to the water
- When the soap solution is added the sulfur sinks to the bottom and disperses
Surface tension is the measurment of how easy it is to break the surface of a liquid. When the paper clip and the sulfur are added to the surface, the hydrogen bonding of the water molecules on the surface is stronger than normal and gives them the ability to float. The soap solution is nonpolar so they weaken the hydrogen bonds that hold the water together at the surface a break the surface, which causes the paper clip and sulfur to go to the bottom.
Density of Water
In the Density of Water lab, my partner and I tested the density but adding dyed green cold water to water that is room temperature and also adding ice to the room temperature water:
- Ice water added to the bottom of the room temperature water stays at the bottom and doesnt mix
- Ice water added to the top of the room temperature water sinks to the bottom
- Ice added to the water floats to at the top
When water is above 4 degrees celsius it behaves normally but at temperatures below 4 degrees celsius to 0 degrees celsius water begins to freeze because the hydrogen bonded molecules stop their rapid movement. The water become dense because the bonds are strong and more spread out when it turns into ice. When cold water is added with room temperature water it sinks because the warm water molecules are less dense and take up less space then cold water does.