Where materials come from: sources and converting them into workable forms

What is the grey core of a pencil made of, the part that leaves the mark? Lead is the obvious answer, because that is what everyone calls it, and it is wrong. The core is graphite, a form of carbon, dug out of the ground and mixed with clay. Graphite was once mistaken for a kind of lead ore, and the name stuck. So how does a lump of grey rock from a mine become the neat core of a pencil you can buy? We will trace that grey rock to a pencil core once the route's stages are named.

Every material starts at a primary source, the place it comes from in nature. Some are grown: timber from forests, cotton from plants, wool from sheep. Paper and board count as grown too, because they are made from wood pulp. Some are mined or quarried, like iron ore, or bauxite, the rock that aluminium comes from. And some are drilled, like crude oil, the starting point for most polymers and synthetic fibres. However different the source, the route to a maker always has the same shape. The material is sourced, then extracted or harvested, then processed, then transported, and it ends in a workable form a maker can buy. Transport also comes between stages, wherever the next machine is. A workable form is the plank, the sheet or the bag of granules that arrives at the factory. Every route in this video ends there, not at the raw material. Now place a stage. Out in a forest, a worker cuts down a pine tree with a chainsaw. Which of the five stages of the route is that? Extracting or harvesting. The tree grew at its source, and felling it is how it is taken.

Now timber, walked in full. A solid pine bookcase is sold in a furniture shop, and this is how its pine reached the maker. Grown: pine is a softwood, grown in managed plantations, where every tree that is felled is replaced by new planting. Felled: the trees are cut down with chainsaws or a harvesting machine, stripped of their branches and cut into logs. Transported: the logs go by lorry, or by ship, to a sawmill. Converted: at the sawmill the bark is stripped off, and each log is sawn into planks and boards. Fresh-sawn planks are full of water. What must happen before they're sold, and why? The planks are seasoned, which means dried, in the open air or in a kiln, a large drying oven. The moisture content falls, so the wood will not warp or shrink later, once it is part of a bookcase. Finished: the dry planks are planed smooth and cut to standard sizes, then sold to the maker as stock planks. That is the workable form, and the end of the route. Here are two openings to that answer. One says: pine comes from trees. The other says: pine trees are felled with a harvesting machine, and the logs go by lorry to a sawmill. Which opening describes how, and what is the other one missing? The second describes how. The first only says where pine comes from, with no action and no machine. One examiner's report names that gap. The majority of candidate responses described where the materials would be extracted from but many descriptions lacked detail of the methods used. The fix is to number your stages and name the tool or machine at each one: chainsaw, sawmill, kiln, planer. A different report, on a later paper, shows what that habit earns. This question was answered well by many candidates. Many candidates gave detailed descriptions of the steps involved in the sourcing and processing of the materials into a useable form and achieved high marks. That makes a route learned in full worth the effort. Walk the stages in order, name the machine at each one, and end on the workable form.

Now a route that looks nothing like a forest. A milk bottle is made from high density polyethylene, HDPE for short, a polymer. What raw material do you think that milk bottle starts out as? Crude oil. A barrel of oil and a milk bottle sit at the two ends of one route, and most plastics begin the same way. Source: crude oil is a fossil fuel, formed over millions of years from the remains of tiny sea creatures and plants. It is drilled from wells on land or under the sea, then sent by pipeline or tanker to a refinery. Refine: at the refinery, fractional distillation separates the oil into parts called fractions, by their boiling points. Crack: long molecules from one fraction are broken into small ones, such as ethene. Ethene is a monomer, a small building block that a polymer can be made from. Polymerise: thousands of ethene molecules are joined into long chains, and those chains are polyethylene. What form will the bottle maker buy it in, and what will it do with it? Granules. The polymer is extruded, squeezed out in strands, which are chopped into small granules, bagged and shipped. At the bottle factory the granules are melted and moulded into bottles. The white bottle in your fridge began as oil from a well, refined, cracked, joined into chains and melted into shape. Every stage is an action done to the material, not just a place it passes through.

Metals follow the same shape of route. Iron ore is mined, and the iron is extracted in a blast furnace, a tall furnace fed with ore, coke and limestone. Aluminium comes from bauxite, and electricity is used to extract it. Here's the route to the steel in a food tin, with one stage missing. Ore is mined, then it goes into a blast furnace with coke and limestone. After the gap, the metal is cast into slabs and rolled into coils. Which stage is missing between the furnace and the slabs, and what does it do? Turning iron into steel. Iron from the furnace carries so much carbon that it is too brittle to be flattened into thin sheet. Oxygen is blown through it while it is liquid, burning most of that carbon off. The full metal route runs like this. Mine the ore, extract the iron in a blast furnace, and blow oxygen through it to make steel. Cast the steel into slabs, roll them into sheet and coil it, ready to sell as stock sheet. Papers and boards take one line: wood is pulped, and the pulp is pressed and dried into reels and sheets. Textiles take one line too: fibres are picked or sheared, cleaned, spun into yarn, then woven or knitted into fabric. Your course asks for at least one material area in full. So learn the route for your own area stage by stage, and know the shape of the others. Here's another trap. A question asks how pine is sourced and processed, and a student writes: cutting down forests destroys habitats. What is wrong with that as an answer to a how question? It answers a different question. A how question wants a sequence of actions, with the tool or machine at each stage. The effect on the planet is a separate topic, with its own questions.

Now back to the pencil core. It starts as graphite dug from a mine, and it ends as the core of a pencil. What has to happen in between to turn mined graphite into a pencil core? The graphite is ground into powder and mixed with clay. The mix is squeezed into thin rods and dried, then fired hard in a kiln. The fired rods are the workable form a factory sets into wood. So the grey core was never lead. It is graphite that has been mined, ground, mixed, shaped and fired, the same route shape as every other material.

To finish, four questions on the route from source to stock.

Cotton for a T-shirt: is its primary source grown, mined or drilled? Grown. It is picked from cotton plants, then cleaned and spun into yarn. Now, logs have just been sawn into planks. Which stage comes straight after that? Seasoning. The planks are dried in the air or in a kiln, so they will not warp or shrink later. Here's a different source: polypropylene for a lunch box. What raw material does it start as? Its raw material is crude oil. Then it is refined, cracked into small molecules, polymerised and sold as granules. Try the pencil to finish: what is the core's source, and what is its workable form? A graphite mine is the source. The workable form is the fired rod of graphite and clay that the factory sets into wood.

If you're sure of all four, the route is yours, and a thumbs up on this video saves you watching it again. If a stage kept slipping, come back to it tomorrow and walk your own area's route once more, because a day's gap is often what makes the order stick.

Next in the chapter: Stock forms, standard sizes and standard components, which picks up the plank, the sheet and the granules where this route leaves them. Hopefully that's next in your feed, but if not, search for ScholaFly D T oh three, oh five.

Every other video is on scholafly.com too, easy to search by video code or by keyword. Whatever you're revising, go there and have a look, or, watch the next video.