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Year 8 Revision booklet One sheet per topic

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1 Year 8 Revision booklet One sheet per topic
Mind map, note or questionnaire type form Some links to the internet For on-line Biology tests go to For on-line Chemistry tests go to For on-line Physics tests go to For a general revision site Year 8 Revision booklet

2 Only fibre (cellulose) is not broken down
8A DIGESTION Food takes about 8 hours to pass through the system: mouth-> Oesophagus-> stomach-> small intestine> colon-> rectum> anus. Only fibre (cellulose) is not broken down Nutrient Use in the body Good sources Carbohydrate To provide energy Cereals, bread, pasta and potatoes Protein For growth and repair Fish, meat, eggs and dairy products Fat To provide energy. Also to store energy in the body and insulate it against the cold Butter, oil and nuts Minerals Needed in small amounts to maintain health Salt, milk (for calcium) and liver (for iron) Vitamins Dairy foods, fruit, vegetables Fibre To provide roughage to help to keep the food moving through the gut Vegetables, bran Water Needed for cells and body fluids Fruit juice, milk, water Special Features Villi (us) are the fingerlike structures located in the small intestine: They have: Thin walls Large surface area Good blood supply so the small soluble molecules can be easily absorbed into the blood circulation Digestion is the process of breaking down large insoluble molecules into small soluble molecules. 2 Ways of breaking down. Mechanical – Teeth Chemical – Enzymes Year 8 Revision booklet

3 The chemical process of making energy
8B Aerobic respiration (with Oxygen) Glucose + Oxygen  Carbon Dioxide + Water +Energy Breathing in Inhaling; Breathing out Exhaling. T= Alveolus, U=Bronchus, V= Bronchiole, W=Lung, X= Heart, Y = Rib, Z = Trachea (windpipe) RESPIRATION The chemical process of making energy Inside the lung Features of the alveolus mean fast gaseous exchange : Numerous 300,000,000 Thin walls Good blood supply Anaerobic respiration (without Oxygen) Glucose  Lactic Acid This causes cramp and gives much less Energy than aerobic respiration Year 8 Revision booklet

4 Microbes and Disease 8C Micro-organisms, or microbes for short, are very small living creatures. They perform the 7 life process (MRSGREN) Microbes (bacterial mould) grow on bread better in warm, wet conditions Yeast is a microbe (fungus) to make bread rise it needs warmth, water and sugar Yeast respires making carbon dioxide and water. The carbon dioxide makes the bread rise! To cause an infection, microbes must enter our bodies. Four ways to enter: Inhaling Cuts to skin Drinking unclean water Eating contaminated food Microbes also perform useful functions such as : Making cheese, yoghurt and wine (fermentation) Bacteria (orange) on the tip of a pin. Magnification x1600 Year 8 Revision booklet

5 Ecological Relationships
8D Ecological Relationships Population Dynamics depend on Predator: Prey Relationships We see that when prey (rabbit) are numerous their predators (lynx) increase in numbers, reducing the prey population, which in turn causes predator number to decline. The prey population eventually recovers, starting a new cycle. Determine a plant population by the quadrat method: Random use of the quadrat Count number of species in quadrat Repeat many times (for a good average) Average per m² multiplied by total area = Population The pyramid of numbers is a useful way of representing a food chain as it shows how the number of consumers at each level decreases, with plants being the most numerous at the base of the pyramid and top carnivores the smallest group. Where the plant being eaten is a tree, however, the pyramid no longer works as a useful model. This is rectified by the use of the pyramid of biomass, where it is the mass of the levels rather than numbers that are represented. REMEMBER 90% of the energy falling on any level of the food chain is used by the species or wasted only 10% is available to the next level of the food chain. Hence food chains are short only 2, 3 or 4 levels. Year 8 Revision booklet

6 Atoms and Elements 8E The Periodic Table holds all the elements in a sensible order. It is made of groups (columns of elements with similar properties e.g. alkali metals, halogens, noble gases) and periods (rows of elements where the element changes from reactive metal on LHS to metal to non-metal to noble gas on RHS. Check out : An Atom is the smallest size of particle which cannot be further subdivided. (atomos is Greek for indivisible) An Element is made up of one type of atom (92 naturally occurring elements) Reactive Metals>> Metals>>>>>>>>>>>…..Non metals>>>>>>>>> Alkali metals Alkaline earth metals Periodic Table Colour groups as shown Noble gases Halogens Year 8 Revision booklet

7 Compounds and mixtures
8F Compounds and mixtures A compound contains different types of atom joined together. The formula tells you the ratio of atoms to each other. A compound is a pure substance. Compounds and elements react (to make new compounds, with new properties) Air is a mixture of oxygen, nitrogen, argon and other gases. Mixtures can be separated by physical means (e.g. liquefaction, evaporation, filtering etc.) Compounds cannot be separated. Carbonates (e.g. Calcium carbonate (limestone or chalk) and copper carbonate, decompose when heated to give off carbon dioxide and leave the oxide, (Calcium Carbonate (heat) calcium oxide + carbon dioxide) with acids carbonates neutralise the acid to give carbon dioxide, water and a salt (calcium carbonate + hydrochloric acid calcium carbonate + carbon dioxide water Year 8 Revision booklet

8 8I Thermal INSULATORS restrict heat flow, Thermal CONDUCTORS allow heat to flow easily. Metals are good thermal conductors; gases are good thermal insulators TEMPERATURE measures the level of heat in a body. We use the centigrade scale. 0°C = freezing point of water; 100 °C = boiling point RADIATION is the transmission of heat energy in the form of waves. Radiation can pass through a vacuum. Solar energy comes to earth by radiation. gbhhy Heating & Cooling EVAPORATION occurs when hotter liquid particles escape into the air, so the liquid disappears and the thing holding it becomes colder. CONVECTION is the transmission of heat in fluids. Hot particles move quicker and expand causing the hot fluid to rise. Conduction causes “thermals” hot air currents near mountains. Coal mines used to use fires to make convection currents to get fresh air into the mine. CONDUCTION is the passage of heat through solids. Hot particles vibrate more knocking into the ones next to them and so the energy passes along the solid. All solids expand slightly when heated. Year 8 Revision booklet

9 Magnets and electromagnets
8J Magnetic materials are iron, cobalt & nickel. Only magnets can repel, unmagnetised iron is attracted to a magnet, copper is not attracted to a magnet because it is not a magnetic material Electromagnets are used for switching on and off secondary circuits using a reed switch. Other uses of electromagnets are in the electric bell and in circuit breaker switches Electromagnets or solenoids are created when current passes through a conductor. Stronger electromagnets are made by: More coils, More current, Adding an iron core Magnets have 2 poles North and South, lines of force () go from North to South. If lines are closer then the magnet is stronger. Like poles repel, unlike poles attract Year 8 Revision booklet

10 8K When light travels through a glass prism the light shows the colours of the rainbow (ROYGBIV). This is called DISPERSION which depends on REFRACTION. White light is made of many colours Light Luminous sources, like the Sun, create light. Non luminous sources like the Moon don’t but we see them because of reflection Light Light travels in straight lines and is shown with an arrow REFRACTION is the bending of light when it moves from one medium to another of different density (e.g. glass to air) Light travels quicker through air than glass that is why refraction occurs Normal (90° to the mirror) Angle of Reflection r Angle of incidence i <i=<r Light from objects enters our eyes MIRROR To see how colours change go to : To see how colours change go to : Year 8 Revision booklet

11 8L Sound travels in longitudinal or compression waves (back and forwards along the direction of the wave). Sound & Hearing The medium is the material through which sound waves travel. They need a medium because they cannot travel through a vacuum. Short, tight thin strings make high frequency or high pitch sounds; Long, loose, thick strings make low frequency or low pitch sounds. AIR Sound & Hearing Vibration is a pattern of movement , up and down or side to Frequency is the rate of vibrations it is measured in cycles per second or Hertz Amplitude is the size of any single vibration and a measure of loudness, expressed in deciBels (dB) To see this in action go to: Outer ear>>>>>>>middle ear>>>inner ear A sound wave is a pattern of vibrations carrying sound energy through the air (or other material) Identify: Ear Drum, 3 small bones, Cochlea, Eustachian tube, semicircular canals, auditory nerve. Year 8 Revision booklet

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