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Science Key Concepts Series

Website: http://www.benchmarkmedia.info

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Build a solid foundation in your knowledge of science by learning a few key concepts in physics, chemistry and biology. Each title in this series explains three key science concepts. Experiments, many of which would be too difficult or dangerous to be conducted in a school lab, illustrate each concept. Artwork and animation illuminate what is happening both visibly and at the molecular level. The process of scientific reasoning and the nature of scientific evidence are demonstrated, with thought-stimulating questions interspersed throughout.

Episodes:

  • Applied Chemistry

    Explore three concepts with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level: Ammonia and Fertilizers / Plastics and Polymerisation / Sulphur and Sulphuric Acid.

    Length: 00:15:16
    Usage rights: 12/1/2012 to 11/30/2017
  • Cells and Tissues

    The three concepts below, each run 5 minutes , and clearly show with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level. Animal Cells: Structure and Tissues Plant Cells: Structure and Tissues Cell Division: Mitosis and Meiosis

    Length: 00:14:55
    Usage rights: 12/1/2012 to 11/30/2017
  • Cellular Energy and Metabolism

    Explore three concepts with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level : Photosynthesis /Respiration /Enzymes.

    Length: 00:15:57
    Usage rights: 12/1/2012 to 11/30/2017
  • Electric Current, Voltage and Circuits

    Explore the interplay in series and parallel circuits of votlage, current, resistance, and electrical devices. CONTENT SUMMARY : The program introduces electric current and voltage and measures these in series and parallel circuits. An experiment to measure resistance is demonstrated and results are shown graphically. Resistance is introduced and calculated from the gradient of V–I graphs. Ohm’s Law is discussed and the V–I graph for a light bulb is plotted. Resistance is shown to depend on the type of metal, the length of a wire, the thickness of a wire and on the temperature, concluding with a demonstration of a superconductor. Animations of positive ions and free electrons explain the observed behaviour. Chapter 1: Current, Voltage, and Circuits (6 min) Small electrical devices require a source of electrical energy, a path for current to flow and a component to work. Electric current is a flow of electrons. An animated model is shown in which an escalator is the source of energy (this is analogous to a battery giving electrons electrical energy). It gives balls (electrons) potential energy by lifting them to a higher level. The balls move around the circuit and a paddle wheel represents a component. The balls turn the wheel giving it kinetic energy and then fall to a lower level, losing potential energy. Current is the amount of charge passing a point in one second. It is measured with an ammeter. Voltage is the amount of potential energy the electrons are carrying. The voltage between two points in a circuit is measured with a voltmeter. Components can be connected in a continuous loop called a series circuit. They can also be connected in a parallel circuit in which each component is connected directly across the power supply and there is more than one path around the circuit. As more bulbs are added in a series circuit the brightness decreases. As more bulbs are added in a parallel circuit the brightness is unchanged. The current is measured in a series circuit. With one bulb it is 0.4A with two bulbs the current is halved and with three bulbs it is reduced to 0.13A. In a parallel circuit, with one bulb the current either side of the bulb is 1.5A. When a second bulb is added in parallel the current from the power supply is doubled to 3.0A, each bulb is taking 1.5 A. When three bulbs are in parallel the total current is 4.5A. The voltage is measured across components in a series circuit and the sum of the voltage across each component is the same as the total supply voltage. In a parallel circuit the voltage across each component is the same as the voltage across the battery. Chapter 2. Ohm's Law (5 min.) A bulb is connected to a power supply and an ammeter measures current while a voltmeter measures voltage. As the voltage is increased, the current increases. More energy is transferred to the bulb, which gets brighter. To investigate this effect, the bulb is replaced by a fine wire. Voltage is increased by regular amounts and current is measured. In general, current increases as voltage increases, but to investigate in more detail a graph is plotted of voltage against current. The graph gives a straight line through the origin showing that voltage is directly proportional to current. The gradient of the straight line is R so V =RI. The experiment is repeated with the wire replaced by a resistor. This graph is plotted on the same axes, giving a steeper straight line. The value of R is calculated and shown to be 5.0 for the wire and 14. 7 for the resistor. R is then explained to be the resistance of the wire or resistor, measured in ohms (symbol W). Resistance is a measure of how difficult it is for electrons to flow through a circuit. The escalator and paddle wheel model is used to describe increasing resistance by changing the paddle wheel for a larger heavier wheel. This wheel is more difficult for the electrons to turn, so they move more slowly and so the current is reduced. As the V–I graphs are straight lines through the origin the wire and the resistor obey Ohm’s Law, which states that, at constant temperature, voltage and current are directly proportional. The graph for a light bulb is then plotted. This graph is a curve so the bulb does not obey Ohm’s Law. Devices like this are said to be non-ohmic. Chapter 3. Factors Affecting Resistance (6 min) Two bulbs are shown. The energy from the power supply is the same, but one is brighter than the other and so they must have different resistance. Two wires made of different metal, but of the same thickness and length, are compared. An ohmmeter is used to measure resistance. One is made of nichrome and has a resistance of 5W. The other is made of tinned copper with a resistance of 0.2W. An animation of the positive metal ions making up the lattice in a sea of free electrons is shown. When a voltage is applied some of the free electrons will move, forming a current. In a low resistance metal, the electrons will move easily giving a higher current. A different metal with fewer free electrons will have a higher resistance. As the electrons collide with the metal ions energy is transferred, so the metal will heat up. A tungsten light bulb will heat up so much that it glows. At a high enough current the filament melts. The effect of changing the length of wire is demonstrated. If the length is halved, what happens to the resistance? It also halves, from 1.4W to 0.7W. If the length is increased the resistance increases. A variable resistor is a long coil of wire. Sliding the handle changes the length of the wire in the circuit. The bulb is brighter with less wire in the circuit because there is less resistance. With two wires there is double the thickness of metal for electrons to flow through so the resistance is lower. This is shown with the lattice animation of a thick wire and a thin wire. Finally the effect of lowering temperature is investigated. The wire is put in liquid nitrogen. The resistance is less. The animation shows that as the positive ions vibrate less it is easier for the free electrons to pass through the lattice. Some materials become superconductors at very low temperatures. In superconductors, the positive ions hardly vibrate at all so there is little or no resistance. A superconductor is put into liquid nitrogen with a magnet on top. The magnet causes a small current in the superconductor and as it cools further this current increases and the magnet levitates. The superconductor produces a magnetic field strong enough to repel the magnet.

    Length: 00:17:26
    Usage rights: 12/1/2012 to 11/30/2017
  • Electricity and Magnetism

    Explore three concepts with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level: Static Electricit / Magnetism / Generating Electricity.

    Length: 00:14:37
    Usage rights: 12/1/2012 to 11/30/2017
  • Electrochemistry

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level: Electrolysis of Molten Lead Bromide and Zinc Chloride / Electrolysis of Sodium Chloride Solution / Electroplating With Copper.

    Length: 00:14:13
    Usage rights: 12/1/2012 to 11/30/2017
  • Electromagnetic Spectrum

    Explore three concepts with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level : The Visible Spectrum / Longer Waves / Shorter Waves.

    Length: 00:14:24
    Usage rights: 12/1/2012 to 11/30/2017
  • Energy Transfer and Biogeochemical Cycles

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level : Food Chain Energy Transfer / The Carbon Cycle / The Nitrogen Cycle.

    Length: 00:15:27
    Usage rights: 12/1/2012 to 11/30/2017
  • Force and Motion

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level: Constant Speed / Acceleration / Gravity and Falling.

    Length: 00:14:58
    Usage rights: 12/1/2012 to 11/30/2017
  • Heat Energy: Transfer and Properties

    The transfer of heat energy, thermal expansion, and specific heat capacity. Chapters: 1. Heat Transfer 2.Thermal Expansion 3. Specific Heat Capacity EDUCATIONAL OBJECTIVES: To help the student understand these key concepts: • heat transfer by conduction convection and radiation • thermal expansion in metal, liquids and gases • specific heat capacity in liquids, and metal. CONTENT Chapter 1. Heat Transfer 8 min. A thermal imaging camera is used to show a saucepan being heated. We can see the hot plate and the heat spreading through the base into the pan. The pan is being heated by conduction. A hot and a cold block are placed in contact and we can see that the cold block warms up as the hot block cools. Eventually they will both be at room temperature. Metals are good conductors. Identical sized metal rods all have a rivet stuck to the end with petroleum jelly. They are simultaneously heated at their other end. The jelly melts soonest on the best conductor. The order from best to worst conductor is copper, aluminium, brass, steel. Liquids are poor conductors as can be shown by holding ice at the bottom of a test tube of water and heating the water at the top until it boils. The ice does not melt. Gases are poor conductors as shown by a thermal image of a flame and by bringing a match very close to the side of a bunsen flame before it lights. Convection occurs in gases. A convection current is set up using a candle flame to heat the air. Smoke is drawn in to show the convection current. Convection also occurs in liquids. A crystal of potassium permanganate is placed at the bottom of a beaker of water. When heated the purple dye from the dissolving crystal shows convection currents. Energy from the Sun reaches us because of radiation. The part of the electromagnetic spectrum for heat transfer is infrared. A grill uses infrared radiation to cook food. All objects absorb and emit radiation which depends on their temperature. Some images using the thermal imaging camera are shown. An ice cream is cold and does not radiate as much as the human face. A dull can and a shiny can are compared. Although they are at the same temperature, but the dull can is radiating more as shown by the thermal image. So the dull can is radiating more heat and will cool more quickly. Chapter 2. Thermal Expansion 6 min. Bridge builders need to know that as solids get hotter they expand. The expanding bar experiment is shown. An iron bar is held tight between a nut and a cast iron pin. The bar is heated and the nut on the end turned so that the bar stays tightly held. When it is cooled it contracts again and the force is enough to snap the cast iron pin. A ball passes through a metal ring, but when the ring is cooled in liquid nitrogen the ball will no longer fit through the contracted metal ring. Railway tracks can buckle in hot weather so either sliding joints are used or expansion gaps are left. Some bimetallic discs are shown. These are brass on one side and iron on the other. Can you explain what will happen when the discs are heated? When heated they will bend, as the brass expands more than the iron. This makes them jump upwards. A candle under a bimetallic strip works as a switch. The candle heats the strip so that it bends downwards, completing the electrical circuit which operates the fan. The fan cools the strip, which straightens again and the fan turns off. This shows how bimetallic strips are used as switches in thermostats. Liquids expand more than solids. Three liquids are compared. They are: water, colored red; methylated spirits, colored blue; and paraffin which is clear. The flasks are placed in a water bath and as the temperature rises the liquid expands up the tube. Methylated spirits expands the most, a similar liquid is used in thermometers. Why is it so suitable? It gives a larger difference in liquid level for a degree change in temperature, which will be easier to read from the thermometer. Gases also expand when heated. When a flask of air has the exit tube placed under water and the air is heated with warm hands bubbles of air can be seen leaving the exit tube. Air is leaving the flask as it expands. If the flask is now cooled it will contract and water is drawn into the flask. If a helium-filled balloon is put into liquid nitrogen the gas contracts. As it is taken out of the nitrogen the balloon starts to reinflate. Why does the balloon re-inflate? Answer: Gas expands as it warms up to room temperature. A flask of air is connected to a glass syringe so that as the gas expands the plunger will be pushed back and the change in volume can be measured. The flask is placed in ice and the plunger moves towards the flask as the gas contracts. The flask is heated and the readings of the temperature and the change in volume of the air in the syringe are noted: Chapter 3. Specific Heat Capacity 6 min. Identical pans containing 200g and 400g of water at the same temperature are heated on identical hobs. Which will boil first? The 200g will boil first. The heat capacity depends on the mass. Does it depend on the material? To find out, the same mass of oil and of water are placed in a pan and heated. When the water reaches 100°C the oil has reached 130°C. This shows that oil has a lower specific heat capacity than water. If Q is the heat supplied then: Q = mc (T2 – T1) where m is the mass (kg), c is the specific heat capacity (J kg-1 °C-1) and T2 – T1 is the change in temperature in °C. Re-arranging gives: c = Q ÷ m(T2 – T1) This equation can be used to calculate the specific heat capacity of a material. An experiment to find the specific heat capacity of aluminium is demonstrated. A 1kg aluminium block has two holes in it, one for an immersion heater and one for a thermometer. The starting temperature is T1 = 27°C and the final temperature after 20 minutes is T2 = 37° C. The mass m = 1kg. If all the heat supplied is received by the aluminium then Q = VIt where V = 5.0V, I = 1.85A and t = 1200s. Then Q = 11100J and c = 11100/10 = 1110 J kg-1°C-1. The actual value is 908 J kg-1°C-1. Can you suggest causes of error and improvement? (Answer: The main error will be heat lost from the aluminium block. This could be reduced by insulating the block.)

    Length: 00:20:18
    Usage rights: 12/1/2012 to 11/30/2017
  • Homeostasis

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level: Controlling Body Temperature / Controlling Blood Sugar / Controlling Water Level.

    Length: 00:15:04
    Usage rights: 12/1/2012 to 11/30/2017
  • Human Body Systems

    Explore three human body systems: lungs, heart, skeleton. Chapters: 1. The Lungs 2. The Heart 3. The Skeleton EDUCATIONAL OBJECTIVES: • the structure of the lungs • exchange of gas in the lungs • ventilation of the lungs • the structure of the heart • how the heart works as a pump • the different structure of arteries and veins • the role of the skeleton in providing support, protection and anchorage for muscles • the importance of bone marrow • the importance of calcium in giving strength to bones.

    Length: 00:15:23
    Usage rights: 12/1/2012 to 11/30/2017
  • Human Digestive System

    See how the human body digests fat, carbohydrates, and protein with these key concepts: • testing for fat, carbohydrate starch, carbohydrate reducing sugars, and protein in nutrients. • the structures and functions of the digestive system's parts. • the specific foods on which some important digestive enzymes and bile salts act. • the effect of pH on the speed at which various enzymes work.

    Length: 00:18:50
    Usage rights: 12/1/2012 to 11/30/2017
  • Molecular Motion

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level: Brownian Motion/ Diffusion / Changes of State.

    Length: 00:14:21
    Usage rights: 12/1/2012 to 11/30/2017
  • Periodic Table: Element Groups

    Element groups in the periodic table have common properties. Chapter 1. Mendeleev's Periodic Table: In 1869, Dmitri Mendeleev, a brilliant Russian chemist, was searching for a possible relationship between an element’s atomic mass and its chemical properties. With the symbol for each then known element (60) and its mass represented on a card, he arranged the cards in order of increasing atomic mass in a series of vertical columns. He then adjusted elements within the vertical columns so that those with similar chemical properties were next to each other in the same horizontal rows. His genius was that where ever an empty space appeared, he predicted an element would be discovered with a given atomic mass and its expected chemical properties. And so they were with approximately the same atomic mass. Since Mendeleev, new discoveries of an atom’s nucleus, which contains protons and neutrons, while electrons orbit the nucleus, has led to a different arrangement of elements in the modern periodic table. Now each element, reading from left to right along a row, called a period, and from top row to bottom, has exactly one more proton in its nucleus. An element’s atomic number equals the number of protons in its nucleus. One proton more or less creates a different element. An element’s atomic mass equals the number of protons plus neutrons it its nucleus. For every positively charged proton in the nucleus of an atom, there is one negatively charged electron circling that nucleus. In the modern periodic table, it is now elements in the same column, called a group, which share the same chemical properties Chapter 2. Noble Gases: Properties and Uses. The six elements, all gases, in the far right column (or group) of the periodic table, group 18, like all groups, share a common structure in their outermost electron shell. That outermost shell, whatever its electron capacity, is always full. That makes these elements extremely non-reactive, and that’s why they are called the Noble Gases. Being non-reactive chemically is a very useful property. Luminescent lights, known as neon lights, are a familiar use of the noble gases neon, helium, or argon or a mixture of them within a clear glass tube. Pass an electric current through the gas, and the color we see is electrical energy absorbed by the gas, then emitted as light energy in a visible color – different gases, different colors. Because there is no chemical reaction, their chemical properties remain unchanged, and these lights can last for up to 30 years. Fluorescent lights have a fluorescent coating on the inside of a glass tube, and are filled with a noble gas. Electrical energy passed through the gas is absorbed and emitted as light energy, which in turn can be absorbed by a variety of fluorescent coatings and then radiated as visible light energy in any one of a spectrum of colors. A welding torch releases a flow of the noble gas argon, so unreactive, it shields the hot metal from oxygen in the air to prevent oxidation or an explosion. Deep divers replace a nitrogen-oxygen mixture with a helium-oxygen mixture because helium being a smaller, lighter molecule than nitrogen, allows for faster passage through body cell membranes during a rapid ascent. The physical property of density in which helium is lighter than air, makes it both useful and safe in airships. An experiment shows that as one goes down the group of noble gases, each is more dense than the preceding one. Chapter 3. Transitional Metals: Properties and Uses. A large block of elements in the middle of the periodic table, are the transitional metals with common properties that are very useful. They are not as reactive as elements in groups 1 & 2 on the far left of the periodic table. All have the following common, useful properties with examples given for each. They are hard for tools; shiny for decorative purposes, malleable, ductile, good tensile strength for construction, conduct heat and electricity well, sonorous for musical instruments, high melting points for safe use as a tungsten light filament, combine in alloys which are stronger & harder than pure metal, as catalysts in automobile catalytic converters to change noxious gases into safe ones. Solutions of transitional metal compounds are colorful, and how they are used artistically as glazes for kiln fired pottery is illustrated.

    Length: 00:16:29
    Usage rights: 12/1/2012 to 11/30/2017
  • Periodic Table: Structures of Atoms

    The periodic table organizes elements according to their properties. Chapter 1. Discoveries of Atomic Structures 6 min Discovery of the Electron J.J. Thomson in 1897 was investigating the then mysterious cathode rays using an apparatus which is replicated in the video. By measuring the deflection of the cathode ray by a positive and a negatively charged plate above and below the ray, Thompson brilliantly calculated that the ray was composed of tiny negatively charged particles, parts of atoms. He had discovered the electron and for that won the Nobel Prize. Discovery of the Nucleus In 1911, Ernest Rutherford’s experiment is replicated in which he passes high energy alpha particles through gold foil, and particle detectors record that most pass straight through, but unexpectedly, a few are deflected backwards. Rutherford reasons that the few deflected particles must have hit a very small dense center in the gold atom, a center he chose to call a nucleus, which was surrounded by vast empty space which was why most of the alpha particles passed straight through. Since Thomson and Rutherford, scientists have discovered many more atomic particles, three of which you should know more about, protons, neutrons, and electrons. Chapter 2. Atomic Numbers and Mass Numbers 5 min. The atomic number is simply the number of protons in the nucleus. There is always one negatively charged electron for each positively charged proton in the nucleus. Hydrogen has one proton so its atomic number is 1. Helium with two protons has the atomic number 2, and Lithium with three protons, has atomic number 3. Each element in the periodic table reading left to right in each row (called a Period), has one more proton, and so has an atomic number which increases by one. The mass number is the number of protons plus neutrons in the nucleus. Hydrogen has one proton, no neutrons, so its mass number is 1. Helium has two protons plus two neutrons, so its mass number is 4. Lithium has 3 protons and 4 neutrons, so its mass number is 7. Chapter 3. Electron Shell Configurations 7 min. Electrons moving around the outside of an atom occupy a series of shells at different distances from the nucleus. This orbital picture is visualized using a group of roller blade skaters, each representing one electron moving around a set of rings drawn on the floor representing electron shells. The players illustrate how the first three shells can hold a fixed number of electrons (2.8.8) and how they fill up starting with the shell closest to the nucleus. The skaters visualize how the electrons fill up shells in Hydrogen (1 electron), Helium (2), Lithium (3), Fluorine (9), Neon (10), and Sodium (11). Elements in the same column, called a group, of the periodic table have the same number of electrons in their outer shell, which gives them similar chemical and physical properties. Group 18 on the far right, the noble gases, has no free electrons on their outer shell, and their common chemical property is virtually no reaction with other elements. In the far left group, group 1, starting with Lithium top left, and reading down the group, each element in this and every other group has one additional shell, which holds a of varying maximum number of electrons. But the outer shell of each element in this group 1, holds just one electron. Reading left to right along a row, called a period, each element will have one additional electron in its outer shell.

    Length: 00:18:24
    Usage rights: 12/1/2012 to 11/30/2017
  • Properties of Natural Resources

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level: The Fractional Distillation of Petroleum / Oxygen and Nitrogen / Reducing Metal Oxide/

    Length: 00:14:42
    Usage rights: 12/1/2012 to 11/30/2017
  • Radioactivity

    Explore three concepts with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level: Detection and Origin / Types and Properties / Measuring and Using Half Life.

    Length: 00:15:21
    Usage rights: 12/1/2012 to 11/30/2017
  • Reactions and Energy Changes

    Explore three concepts below with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level: Exothermic and Endothermic Reactions /Reaction Rates / Catalysts.

    Length: 00:15:56
    Usage rights: 12/1/2012 to 11/30/2017
  • Reactivity of Elements

    Explore three concepts with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level: Highly Reactive Metals, Group 1, Periodic Table / Highly Reactive Halogens, Group 17, Periodic Table / Range of Reactivity among Metals.

    Length: 00:14:18
    Usage rights: 12/1/2012 to 11/30/2017
  • Sensory Responses and Tropisms

    Explore three concepts clearly shown with excellent experiments and computer animation what is happening visibly during the experiments and invisibly at the molecular level: The Eye / The Nervous System / Plant Tropisms.

    Length: 00:15:20
    Usage rights: 12/1/2012 to 11/30/2017
  • Waves

    Explore three concepts with excellent experiments and computer animation showing what is happening visibly during the experiments and invisibly at the molecular level: The Nature of Waves: Transverse and Longitudinal / Reflection of Waves / Refraction of Waves.

    Length: 00:14:04
    Usage rights: 12/1/2012 to 11/30/2017

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