it's harder to make
aluminum is more durable than iron.
every metal is priced based on scarcity, and ease of access. there's a lot more iron than aluminum in the ground... and aluminum's properties and usage for current products make it more expensive. it also cools very quickly, while still being lightweight and durable... making it very useful.
Both iron and aluminum will oxidize. When iron oxidizes the product (rust) easily crumbles away, exposing more iron to oxidation. Aluminum is even more reactive than iron, but the aluminum oxide that forms is one of the hardest known substances and forms a protective layer that, even though it is microscopic, shields the aluminum from corrosion.
The iron chunk will be denser and heavier than the aluminum chunk due to the higher density of iron compared to aluminum. Iron is also more susceptible to corrosion compared to aluminum.
Aluminium would be too brittle, light, and expensive
Aluminum used to be more expensive than gold. In Napoleon's time the chemists hadn't discovered a good way to purify aluminum so pure aluminum was expensive and rare. Aluminum used to be a status symbol because it was more expensive and rarer than gold.
gold is more expensive than iron simply because iron is more common and gold is also a purer metal
For homework: Aluminum is about 7 times more expensive than steel. A full answer: Basically: Aluminum is more expensive. And during 2011 is expected to go higher, because of less demand. Although the price of steel is constantly on the raise. BUT, in some cases making things from steel can turn out to be more expensive. Like boats. But again, in the usual case Aluminum is more expensive. How much more expensive depends: There are different kinds of steel. Also, it depends on how much material you'll need. Sometimes a small amount of aluminum will suffice for a much larger amount (in weight) of steel you would need for the same task. In that case making your project from aluminum will cost less than from steel. But the raw cost of steel is still cheaper than that of aluminum. (The reason is that aluminum, although more "abundant" - meaning found more on the surface of earth, is harder and therefore more expensive to retrieve). The most significant cost difference, is the cost of work: tools, knowledge and the price for fixing mistakes. Working with aluminum is much more expensive than steel. In 2002 (before the price rise of steel) it was 4.2 times more expensive to make a car from aluminum, than from steel. But then a comparison by a boat maker shows that its EASIER to work with aluminum, if you use its features to your advantage: (No need to paint submerged parts, build without bending, use standard profiles etc.) and easier to sell. And then it depends if you need to use new material or can use scrap. Today (March 2011) iron ore (the main part for making steel) is 4 and a half cents per pound, while aluminum is a dollar and 14 cents! 0.045 vs 1.14. That's Aluminum over 25 times more expensive than iron. (But then again, steel is about 3.5 times more expensive than iron, so aluminum is about 7.2 times more expensive now. Please understand that a shortage (like the one during the Chinese Olympics a few years ago) can make the price of steel rocket up, and change everything. So you never know what will be. But currently, Aluminum is more expensive. By the way, Mary Antoinette had a set of cutlery (knife, fork and spoons) from aluminum, that was at that time just discovered, and more expensive than silver.
Aluminum conducts heat faster than iron. This is because aluminum has a higher thermal conductivity value compared to iron, meaning it can transfer heat more efficiently.
Iron was used for thousands of years before aluminum. While aluminum is more abundant, it is not as easy to work with as iron.
AnswerThe question may better be written as, "Which steel is harder than which aluminum?" There are many grades of both, and some alloys of aluminum are actually harder than some grades of steel. For instance, 7075-T6 aluminum at 150 Brinell hardness is harder than low-carbon steel at 120 Brinell. Generally speaking, however, steel is harder than aluminum.
Aluminum is more reactive than iron, meaning it can displace iron in a chemical reaction. In practical terms, this means aluminum will react with certain substances that iron will not.