There is a Leaves (Part One) which you could look at before this if you are in any doubt about your leaf knowledge. The above is a cross-section through a typical leaf. There is an actual microscope photograph of a similar leaf below. It should be fairly easy to compare structures between the two pictures. …
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Copper…
After iron and aluminium, copper is probably the third most important industrial metal. It is used in electrical wiring and for printed circuit boards (PCB). The board is completely coated in copper then copper is etched away to leave the path that the electricity needs to follow. Copper is also used for plumbing although it is …
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Units and Calculations…
There are not a great many types of calculation you will be asked to do at this level. You may be asked about speed, density, pressure or perhaps calculating weight from mass and the force of gravity. The question will usually give you enough information for you to work out what sums you need to …
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Leaves (Part One)…
Leaves are the factories of plants. They have a large surface area for gaseous exchange. They can absorb gases from the air through the tiny pores on their undersides called stomata (singular stoma). They also open and close these to regulate water evaporating from the leaf.
Conservation Of Mass…
When a chemical reaction occurs, mass/matter is conserved. This means that the reactants and the products have the same mass. No new atoms are created during the reaction and no atoms are destroyed; they are just rearranged. The following short video attempts to illustrate this principle and although it contains a rather big mistake, it …
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What Have The Romans Ever Done For Us…
Work done by Dr Nikola Koepke (formerly from Oxford University but now at Zurich Universtory) looked at the remains of skeletons from the 8th century BC until the 18th century AD and used changes in people’s heights over this period as a measure of how well fed they were. The study combined biology and archaeology …
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The Hills Are Alive With…
Sound travels as waves at about 340 m/s in air and if you can’t remember some of the terminology about waves you might look here at a previous post. You could also look at this excellent page to play with an animation exploring amplitude, frequency and wavelength. (Don’t forget that you can also use the …
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Sacrificial Protection…
Steel is an alloy of iron containing other elements to improve its physical properties. Mild steel is iron with about 0.25% carbon added; stainless steel is iron with chromium and nickel added to reduce rusting. Iron will rust whenever it comes into contact with both water and oxygen. If you can stop one of those …
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Blast Furnace…
Iron is extracted from its ore (rocks rich in iron oxide) in a blast furnace. The iron ore is mixed with coke (a refined form of coal with a very high carbon content) and limestone. This mixture is baked into a crusty mixture known as sinter (that has a very high surface area) before being …
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Rusty Hinge…
Iron, even in the form of steel, is prone to rust. This is a slow reaction that takes place when the iron is in contact with both water and oxygen. It is quite easy to show that water and oxygen are both needed for rusting by setting up a simple controlled experiment. Things you need …
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