Today in class discussed water and its many properties. One of its most important properties is its ability to go through the process of cohesion and adhesion. Cohesion is the ability of water to bond with itself and adhesion is the ability of water to attach itself to something else. Water also has a special kind of bond called hydrogen bonds. Hydrogen bonds are weak and give water the ability to break bonds without using too much energy which is very important in living organisms. Water also has more heat capacity then other molecules and its boiling point is 100 degrees Celsius. Water molecules are special because they expand when they freeze and their atoms become more rigid. When frozen, its density also decreases because is mass decreases but its volume does not.

After the lecture, we did an experiment testing the the cohesion and adhesion of water. First we dropped water onto pennies until it created a convex surface:

Why convex?

because water uses cohesion to bond and grow on top of each other.

But why convex?

because the tangent angle at which water grows forces it to take a convex shape.

 

After doing this a few times he asked us to use a toothpick to prod the surface a few times and observe how the water interacted with it:

 

here we can see the process of adhesion taking place as the water molecules attach themselves to the toothpick.

 

After this we dipped the toothpick in some dish soap (surfactant) and poked the convex  surface:

 

 

althogh we had some trouble, we were eventually able to break the convex bubble.

 

Once the experiment was done we took a quick chemistry quiz and left for lunch :).