I looked in my book and I can't find the answers to these questions! Can anyone help me? :)
Question #1: Why do liquids in a graduated cylinder form a meniscus?
Question #2: Give three examples of amorphous solids. I have glass, can anyone give me two more!
Thanks :) !
Without getting into a discussion about adhesive and cohesive forces, the water wets the inner wall of the graduated cylinder and capillary action pulls the water upward on the glass surface. The center of the water, however, does not have this capillary action with the glass surface. Those molecules in the central section are pulled inward by intermolecular forces (hydrogen bonding in the case of water) and they tend to pull the water molecules inward. So the upward pull at the glass surface and the inward pull on the molecules in the central part of the meniscus, makes the meniscus. It looks, more or less, like this (but I can't draw a curve), '-'. By the way, not all liquids do this. Mercury, for example, a liquid, does not wet the surface of glass and the meniscus is like that of water but upside down.
Examples of amorphous solids are glass, plastic, leather, cotton candy.
Thanks :)
Of course, I can help you with your questions! Let's take them one at a time:
Question #1: Why do liquids in a graduated cylinder form a meniscus?
To understand why liquids in a graduated cylinder form a meniscus, we need to explore the concept of cohesion and adhesion. Cohesion refers to the attraction between molecules of the same substance, while adhesion refers to the attraction between molecules of different substances.
A meniscus forms when the liquid molecules exhibit stronger cohesive forces compared to their adhesive forces with the container (in this case, the graduated cylinder). This difference in forces causes the liquid to either concave or convex at the surface.
The formation of a meniscus is due to the adhesive forces between the liquid molecules and the walls of the container. In the case of a graduated cylinder, which typically has a hydrophilic or water-attracting surface, the liquid molecules are more attracted to the walls of the container. This attraction pulls the liquid up along the sides of the cylinder, creating a upward or convex meniscus, such as in water.
If the liquid has stronger cohesive forces than adhesive forces, the meniscus will be downward or concave, as seen in mercury.
Question #2: Give three examples of amorphous solids. You mentioned glass, and here are two more examples:
1. Plastic: Many types of plastic, such as polyethylene and polystyrene, exhibit an amorphous structure. These materials lack a well-defined repeating pattern at the atomic or molecular level, resulting in a disordered arrangement of particles.
2. Rubber: Natural rubber, as well as synthetic rubbers like neoprene and butyl rubber, are amorphous solids. Like plastics, rubber lacks a long-range repeating structure, giving it unique properties such as elasticity and flexibility.
Remember, if you can't find specific answers in your book, it can be helpful to search online resources, scientific databases, or consult with your teacher or classmates for additional information.