Senior Science Half Yearly Revision

Topics: Surface tension, Surfactant, Vitamin Pages: 4 (1208 words) Published: April 23, 2010
Senior Science Half-Yearly Revision

1. Surface tension - A property of the surface of a liquid. It is what causes the surface portion of liquid to be attracted to another surface, such as that of another portion of liquid. Surface tension is caused by cohesion (the attraction of molecules to like molecules). Since the molecules on the surface of the liquid are not surrounded by like molecules on all sides, they are more attracted to their neighbours on the surface.

Mercury has a high surface tension. The meniscus of water is concave whilst the meniscus of mercury is convex.

When a water strider is on the surface of the fluid, the surface under tension will behave like an elastic membrane. There will be a small depression on the surface of the water. The vertical components of the forces by the molecules on the object will balance out the weight of the object.

2. Biomaterials are special materials that are biocompatible. They are able to function in contact with the living tissue with minimal rejection from the body. A biomedical device are implants that are engineered from biomaterial and designed to perform specific functions of the body.

Titanium alloy – low-density, non-toxic, biocompatible, strong, and non-corrosive. Plastics (polymers) – biocompatible, not-toxic, non-corrosive, smooth, flexible, and low-density.

3. Muscles – Muscles look like bundles of pale pink tissue which pull the bone. Tendons - Tendons are shiny white tissues at the ends of the muscles that attach muscles to bones. Ligaments - Ligaments connect bones to other bones at joints. They look like a shiny white covering of the joint surfaces. Cartilage - Between the bones is another shiny white material that is slippery. This is cartilage, which helps the bones move without grinding against one another, or without causing trauma.

4. Why is it important for detergents to be biodegradable – Non-biodegradable detergents could build up in waterways and cause significant and...
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