Senior Science Half Yearly Revision

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 long-term damage. Biodegradable can be broken down by the action of living things like bacteria and other microbes. 5. Transdermal Patches – Slow and steady drug release directly into the bloodstream is the main benefit of skin patches. The drug is encased in a polymer which slowly releases the drug. E. g. Nicotine patches.
Subdermal Implants – Devices implanted under the skin are also being developed to deliver drugs at a controlled rate. E. g. Contraceptives. It consists of six flexible silicon tubes filled with a five-year supply of the contraceptive hormone. It is implanted in the upper arm, and small amounts of the hormone continuously seep through the permeable tubes into the bloodstream. 6. Water is important in making medicines because generally, the more water soluble a drug, the quicker will be its absorption. It can be administered orally (as solutions, or in capsules or tablets) and by injection. Water acts as a solvent. . What causes the sound of a heartbeat – The first heart sound (lub) is caused by the acceleration and deceleration of blood and a vibration of the heart at the time of the closure of the tricuspid and mitral valves. The second heart sound (dub) is caused by the same acceleration and deceleration of blood and vibrations at the time of closure of the pulmonic and aortic valves. Basically, the sound comes from the heart valves closing. 8. Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids.
Surfactants improve water’s ability to wet things, spread over surfaces, and seep into dirty clothes fibres. One end of their molecule is attracted to water, while the other end is attracted to dirt and grease. So the surfactant molecules help water to get a hold of grease, break it up, and wash it away. Soaps and detergents are both emulsifying agents and surfactants. 9. Colloid – a type of mixture in which one substance is dispersed evenly throughout another. Particles that remain suspended for a long time. Suspension – a mixture containing particles that settle out or form layers.
Particles that settle out or form layers. Solute – the substance to be dissolved. Solvent – the substance in which to be dissolved in. Solution – a group of molecules that are mixed up in a completely even distribution. Dissolved substances. Mixture – is when two or more different substances are mixed together but not combined chemically. 10. Non-invasive medical techniques – X-ray and Ultrasound. Advantages – does make an incision into the skin and short or no hospital stay. Disadvantages – may not be able to detect all problems.
Minimally invasive – Keyhole surgery and Angioplasty. Advantages – get a detailed diagnostic report. Disadvantages – long hospital stay. 11. Hydrophilic – refers to a physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. Heads stick in the water, tails stick out of the water. Hydrophobic – is the physical property of a molecule that is repelled from a mass of water. Tails stick in the water, heads stick out of the water. 12. If plaque or fats get deposited in the arteries, it slowly blocks blood from flowing freely to the heart.
Plaque deposits that have built up inside arteries can be reduced by the technique called angioplasty. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size. The balloon crushes the fatty deposits, so opening up the blood vessel to improved flow, and the balloon is then collapsed and withdrawn. 13. Lubricants: Use – Reduces friction between moving parts. Precautions – Some are flammable-keep away from flames. Pesticides: Use – Kills pests.
Precautions – Toxic-do not swallow, inhale or spill on skin. Solvents: Use – Dissolves dirt on clothes, turpentine to clean paintbrushes, oven cleaners to dissolve fat. Precautions – Some are flammable and toxic. Drain and oven cleaners are corrosive and will burn skin badly. Do not swallow, inhale or spill on skin. Cosmetics: Use – Perfumes to produce a fragrant and pleasant scent. Make-up to change appearance. Hair gel to change a particular hairstyle. Precautions – May cause an allergic reaction in susceptible people. Sprays may be dangerous to inhale.
Preservatives: Use – Prevent bacteria growing in food. Precautions – May cause illness if eaten. Sulphur dioxide may cause asthma. May cause learning difficulties. 14. Diagram of the Heart 15. Parts of the Digestive System 16. The pH of the stomach is between 2 -3. This acidic condition will help kill bacteria and mix the food with digestive juices. The pH of the small intestine is between 7. 5-8. This alkaline condition helps in complete digestion and absorption of the food. 17. Role of skin – Helps maintain a constant body temperature.
Micro-flora – Protects the body from disease. 18. Water-soluble vitamins: 8 B vitamins and vitamin C. Fat-soluble vitamins: Vitamins A, D, E and K. Water-soluble vitamins dissolve easily in water, and in general, are readily excreted from the body, to the degree that urinary output is a strong predictor of vitamin consumption. Because they are not readily stored, consistent daily intake is important. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). They are more likely to accumulate in the body.