Video Transcript
Which of the following properties is not correct for pure iron? (A) Pure iron has a shining luster. (B) Pure iron has magnetic properties. (C) Pure iron has a low melting point. (D) Pure iron is very soft with low hardness. Or (E) pure iron is easily pulled or stretched into a wire.
This question is asking about the physical properties of pure iron. As we will see in a moment, some of these properties are properties of metals in general, while other properties are specific to pure iron. Keep in mind, this question is asking us to find the property that is not correct for pure iron. In other words, four of the answer choices will be properties of pure iron. And the correct answer will be the one that is not a property of pure iron.
First, we can say that, like most metals, pure iron is lustrous and ductile, lustrous meaning its outer surface can be polished to have a shine and ductile meaning it can be easily pulled or stretched into a wire. These properties correspond to answer choice (A) and answer choice (E). Since they are properties of iron, we can eliminate these answer choices from consideration.
One property specific to a small group of metals is that iron is magnetic. Other magnetic metals include nickel and cobalt. Since pure iron does indeed have magnetic properties, we can eliminate choice (B) from consideration.
While we might think of a metal as a stereotypically hard substance, compared to other substances, iron is actually quite soft. It is easier to dent, cut, or otherwise change the shape of pure iron compared to other substances. To increase the hardness of iron, we can make an alloy, adding carbon to make steel. Since iron is soft with a low hardness, we can eliminate choice (D) from consideration.
The melting point of iron is 1538 degrees Celsius. We can say that pure iron remains a solid at high temperatures. In other words, it has quite a high melting point. So this last answer choice, answer choice (C), does not accurately describe pure iron, making it the correct answer.
Like many other metals, pure iron is lustrous and ductile. Like some other metals, it is magnetic and soft. But it does not have a low melting point. So which of the following properties is not correct for pure iron? That’s choice (C). Pure iron has a low melting point.