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Wednesday, March 31, 2010

general science#11

PHYSICS

PRESSURE
  1. Units
    • atmosphere, technical atmosphere
    • mm, cm, inches of mercury
    • mm, cm, inch, foot of water
    • kip, ton-force, pound-force
    • pound per square inch
    • bar, decibar, millibar
    • barye, dyne
    • sthene per square metre, pieze
  2. Pressure in everyday life
    • Transpirational pull in plants (negative pressure caused by surface tension), used to suction water from the water to leaves
    • Casimir effect: physical force betwen two uncharged metal plates in vaccuum. Used in nanotechnology
    • Atmospheric pressure decreases with elevation. Due to this boiling point of water decreases with elevation
    • Blood pressure is the pressure exerted by circulating blood on the walls of blood vessels. For a healthy adult human the pressure should be 115 mm Hg (systolic) and 75 mm Hg (diastolic)
    • A microphone works on the principle of sound pressure. A thin membrane converts sound pressure into an electrical signal
    • Caisson Disease (aka The Bends or Decompression Sickness) occurs due to sudden change in atmospheric pressure. It happens when a person moves from a high pressure environment to a low pressure. Examples include divers returning from depth, workers in caissons during bridge construction, sudden drop in aircraft pressure etc. Can lead to paralysis and death.
    • Vaccuum is a volume of space where pressure is less than atmospheric pressure. Examples include vaccuum cleaners, deep space, incandescent light bulb
GRAVITATION
  1. History of gravitational theory
    • 4th century BCE: Aristotle proposed heavy bodies are attracted towards the center of the universe due to an inner gravitas
    • 628 CE: Brahmagupta recognized a force of attraction. He followed the Heliocentric solar system and propsed gravitational attraction between the Sun and the Earth
    • 1660s: Robert Hooke explains celestial gravity
    • 1687: Isaac Newton proposes law of universal gravitation
    • 1915: Albert Einstein proposes theory of general relativity
  2. Gravitation in everyday life
    • Objects falling freely towards the earth’s surface have an acceleration due to gravity  g = 9.8 \frac{m}{s^2} This is also known as g-force
    • Escape velocity is the speed needed to break free from a gravitational field. On the surface of the Earth it is 11.2 km/s
    • Weightlessness occurs in orbit when all gravitational forces acting on an object are uniformly distributed. Weightlessness does not occur due to an absence of gravity.

CHEMISTRY

CERTAIN COMMON SUBSTANCES
  1. Hydrogen
    • Has same atomic number and atomic weight: 1
    • Most abundant element in the universe
    • Is the lightest element
    • isotopes are Protium, Deutrium, Tritium
    • Heavy water: water which has Deutirum instead of Hydrogen. Obtained by electrolysis of water. Used as moderator in nuclear reactors
    • Used to prepare vanaspati by hydrogenation of vegetable oil
  2. Oxygen
    1. Most abundant element on earth’s crust (50% of all elements)
    2. Used for artificial respiration, and along with Nitrogen as an anesthetic
  3. Water
    • About 70% of earth’s surface and 65% of body weight
    • Hardness of water due to dissolved salts of Calcium and Magnesium
    • Temporary hardness due to bicarbonates of Ca and Mg. Can be removed by boiling
    • Permanent hardness due to chlorides and sulphates of Ca and Mg. Can not be removed by boiling
    • Rain water is the purest form of water
    • River water is hard water
    • Spring water purer than river water
    • Sea water is hard water. Contains Sodium Chloride in addition to salts of Ca and Mg
    • Mineral water: spring water with minerals and having medicinal value
  4. Nitrogen
    • Most abundant in atmosphere (78%)
    • Occurs in animals and plants in the form of protein
    • Used to manufacture fertilizers and explosives
    • Liquid nitrogen used in refrigeration
  5. Phosphorus
    • Found in bones, brain and urine
    • Glows in dark
    • Red phosphorus used to make matches
    • White phosphorus used in smoke screens
  6. Carbon
    • Second most abundant element in human body after Oxygen
    • Occurs in free state as diamond, coal and graphite
    • Diamond: purest form of carbon, hardest naturally occurring substance
    • Graphite: only non-metal to act as a good conductor of electricity. Used to make lead pencils and lubricants
    • Coal: formed by bacterial decomposition of plant material. Peat coal has lowest carbon content (60%), anthracite has highest (90%)
    • Carbon gas: not a gas. Obtained by heating powdered coal and tar in absence of air. Good conductor of electricity
    • Coke: obtained by heating coal in absence of air. Used as household fuel and in steel industry
    • Wood charcoal: obtained by burning wood. Used to make gas masks, acts as bleaching agent
    • Bone charcoal: obtained by destructive distillation of bones. Used as a decolouring agent in sugar industry
    • Lamp Black: obtained by burning vegetable oil. Used to make printer’s ink and boot polish
  7. Sodium
    • Does not occur in free state
    • Highly reactive, always kept under kerosene
    • Used to make sodium vapour lamps
    • Removes traces of water in alchohol manufacturing
  8. Silver
    • Best conductor of electricity
    • Used to make jewellery, mirrors and hair dyes
  9. Gold
    1. Highly inert, does not react with water, air, alkalies or acids. Dissolves in aqua regia. Used to make electron microscope
  10. Aluminium
    1. Third most abundant on earth’s crust (8%)
    2. Used to make cooking utensils, transmission wires, paint
    3. Alloys Duralumin and Magnalumin used in aircraft building
HALOGENS
Halogen
Occurrence
Uses

Fluorine
Gas
Found in soil, sea water
Found in tooth enamel
  • Refrigerant
  • Toothpaste
  • Fungicide
  • Polythene (Teflon)

Chlorine
Gas
Found in common salt
  • Chlorination of water
  • Bleaching
  • DDT manufacture
  • Anesthetic
  • Tear gas

Bromine
Liquid
  • Silver Bromide for photographic plates
  • Added to petrol to avoid lead accumulation

Iodine
Solid
Found in sea water, sea weeds
Found in thyroid gland
  • Tincture iodine, iodex
  • Added to salt to avoid goitre
COMPOUNDS OF SODIUM AND THEIR USES
Compound
Uses

Sodium peroxide
  • Bleaching agent

Sodium hydroxide (caustic soda)
  • Soap
  • Paper
  • Petroleum refining

Sodium carbonate
  • Glass
  • Washing soda
  • Softening water
  • Petroleum refining

Sodium bicarbonate (baking soda)
  • Baking powder
  • Fire extinguishers

Sodium chloride (common salt)
  • Food

Sodium nitrate (Chile saltpetre)
  • Food preservative
  • Fertilizer
  • Explosives
  • Dyes

Sodium sulphate (Glauber’s salt)
  • Glass
  • Soap

Sodium thiosulphate (hypo)
  • Photography
  • Textiles
COMPOUNDS OF POTASSIUM AND THEIR USES
Compound
Uses

Potassium hydroxide (caustic potash)
  • Soap

Potassium bromide
  • Photography

Potassium nitrite (nitre)
  • Gun powder

Potassium chlorate
  • Explosives
  • Germicide

Potassium carbonate (potash)
  • Glass
ALLOYS OF COPPER AND THEIR USES
Alloy
Components
Uses

Bell metal
Copper, Tin
  • Making bells
  • Utensils

Brass
Copper, Zinc
  • Utensils
  • Cartridges

Bronze
Copper, Tin, Zinc
  • Utensils
  • Coins
  • Statues

German silver
Copper, Zinc, Nickel
  • Utensils
  • Coils

Gun metal
Copper, Tin, Zinc
  • Guns
  • Gears
  • Casting

BIOLOGY

HISTORY OF CELL STUDIES
  1. 1665: Robert Hooke discovers cells in cork
  2. 1839: Theodor Schwan and Matthias Jakob Schleiden found cell theory
  3. 1931: Ernst Ruska builds first Transmission Electron Microscope at the University of Berlin
  4. 1953: Watson and Crick discover double helix structure of DNA. They, along with Maurice Wilkins, won the Nobel Prize in Physiology or Medicine in 1962
GENETIC MATERIAL IN A CELL
  1. DNA used mainly for storing genetic information
  2. RNA used mainly for information transport. Sometimes used for genetic storage in certain viruses
  3. Human cell encodes genetic information in DNA
  4. Human genetic material found in nuclear genome and mitochondrial genome
  5. Nuclear genome divided into 23 pairs of DNA molecules called chromosomes
  6. Mitochondrial genome codes for 13 proteins used in mitochondrial energy production
COMPONENTS OF A CELL
  1. Cell Membrane
    • Separates interior of a cell from outside environment
    • Semi-permeable
    • Made of proteins and lipids
    • Protein receptors are found on the cell membrane
  2. Cytoplasm
    • Part of a cell enclosed withing cell membrane
    • Contains three major elements: cytosol, inclusions, organelles
  3. Cytosol
    • Translucent fluid made of water, salts and organic molecules
    • Makes up 70% of cell volume
    • Contains protein filaments (that make up the cytoskeleton) and vault complexes
  4. Inclusions
    • Small insoluble particles suspended in cytosol
    • Include energy storage materials such as starch and glycogen
  5. Organelles
    • Compartments withing the cell that have specific functions. Eg: mitochondria, golgi apparatus, lysosomes etc
  6. Mitochondria and Chloroplasts
    • Both generate energy in the cell
    • Mitochondria uses Oxygen to generate ATP
    • Chloroplasts generate carbohydrates and Oxygen from carbon dioxide and water
    • Mitochondria found in plants and animals. Chloroplasts found only in plants
  7. Ribosomes
    • Large complex of RNA and protein molecules
  8. Nucleus
    • Contains chromosomes
    • Site of DNA replication and RNA synthesis
  9. Golgi Apparatus
    • Found in eukaryotes only
    • Process and package proteins and lipids synthesised by a cell
  10. Lysosomes and Peroxisomes
    • Lysosomes have digestive enzymes
    • Digest excess or worn-out organelles, food particles, virus/bacteria
    • Peroxisomes have enzymes that rid the cell of toxic peroxides
  11. Vacuoles
    • Store food and waste
FUNCTIONS OF A CELL
  1. Cell metabolism
    1. Cell metabolism required for cell growth
    2. Metabolism is the process by which cells process nutrient molecules
    3. Catabolism: cell produces energy by breaking down complex molecules
    4. Anabolism: cell uses energy to construct complex molecules and perform other functions
  2. Cell division
    • Required for building tissue and procreation
    • Prokaryotic cells divide by binary fission
    • Eukaryotic cells divide by mitosis or meiosis
    • Mitosis produces two identical daughter cells, meiosis produces two daughter cells each with half the number of chromosomes
    • DNA replication is required every time a cell divides
  3. Protein synthesis
    • New proteins formed from amino acids
    • Consists of two steps: transcription and translation
ASK AND TELL…
  1. Prokaryotes are
    1. animals without developed nervous systems
    2. organisms lacking nucleus
    3. primitive plants without vascular systems
    4. plants that do not produce flowers and fruits
  2. Honey that has high concentration of sugar does not decay because
    1. it contains natural anti oxidants that prevents bacterial attack
    2. bacteria can’t survive in active state in a solution of high osmotic strength as water is drawn out
    3. bacteria can’t survive in active state as it is deprived of oxygen
    4. none of these
  3. The number of chromosomes in a bacterium is
    1. 1
    2. 2
    3. 4
    4. varies with species
  4. Granum is a component of
    1. chloroplasts
    2. golgi apparatus
    3. ribosomes
    4. starch grains
  5. In a plant cell, DNA is found in
    1. chloroplasts
    2. mitochondria
    3. nucleus
    4. all these

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