What does an avocado seed has to do with physics?

Growing an avocado tree from seed goes viral on the Internet.  Numerous videos that document the growing plant are to be found on YouTube. The base of the method is to place the seed supported by three/four toothpicks in water.  And here is what a trained physicist's eye spots immediately: the MENISCUS.

There are two menisci (yes, this is the plural) visible in the pictures. 

• A concave meniscus occurs when the liquid is attracted to a surface of another object (adhesive forces).  In the picture, it looks like the water claims the wooden toothpick. 
• A convex meniscus occurs when the forces between liquid particles are stronger than between the particles and the surface (cohesive forces).  Here demonstrated at the surface of an avocado seed.

  

Rain Clouds above Lake Michigan

Will the bag pop?

What do you think will happen if I stick all these pencils through this bag full of water? Will the bag pop?

• HOW DOES IT WORK?

The zipper-lock plastic bag is made out of a polymer called low-density polyethylene (LDPE). LDPE is used all over the world for packaging because it is low in cost, lightweight, durable, a barrier to moisture, and very flexible. The bag’s flexible property helps to form a temporary seal against the edge of the pencil so it can go through properly without breaking the bag.

• WHAT I LEARNED FROM THIS EXPERIMENT

The force needs to be (pencil) perpendicular to the surface (zip-lock bag).  How to apply Pascal's principle and formula to my experiment.  How force and area will equal to your pressure.  Why pressure has to be equal everywhere to get accurate results.

(By Rachel)

Floating Needle

A needle has a higher density than water. Normally, it falls directly to the bottom of the water. But when the needle is put into the water horizontally with caution it can float due to surface tension. The water keeps its round shape because there are no water molecules outside the surface to balance this inward pull. Putting the needle horizontally to the surface of the water has a larger contact area and less pressure is exerted on the water surface. (Breanna)

The Rainfall

Heavy rain above a city.