What is the difference between a physical change and a chemical change?

Question

Accepted Answer

Welcome back everyone. Which of the following statements correctly describes a physical and chemical change. Choice A states that a physical change results in the formation of a new substance and that a chemical change only results in the physical state changing for a substance. Whereas choice B states that a physical change results in the change in the physical state of a substance. But a chemical change results in the formation of a new substance. And choice C which states that both physical and chemical changes alter the physical and chemical composition of a substance at the same time. So let's begin by outlining some facts beginning with the fact that for a physical change, we would maintain the substances identity. So we would say that the change in the substances identity is equal to no. So that won't happen. Whereas the change in state in physical state of our substance will occur with a physical change. So an example we can consider would be when we have ice which melts and goes from liquid to its solid face. So that is just a change in physical state when ice melts when it goes from its liquid state to its solid physical state. Now let's outline second, what a chemical change would be characterized by. So for a chemical change, we would observe a change in the substances identity. So we'll say that yes, that that happens. And as far as a change in state, we can also say yes for that. And that is due to the fact that a new substance is going to be formed when we have a chemical change. So for example, we can consider when iron rusts, when iron rusts, iron will say F E for iron, as its chemical symbol will react with oxygen gas. So we've got iron three plus reacting with oxygen gas, which forms as a product, iron three oxide, F E two oh three and that is a solid. So this is an entire new substance and that is how we know that when iron rusts, we have a chemical change. So based on these facts that we've outlined, going back to our answer choices, we're going to rule out choice. A which as we stated, said that a physical change results in the formation of a new substance that would be false and incorrect because that correlates to a chemical change. And we would also rule out choice C because as we read earlier, it states that a physical and chemical change can both alter the physical state and chemical composition. But we determined that a physical change will not alter the chemical composition of a substance And so that leaves us with choice B as the only correct choice which states that a physical change is a process that only results in a change in the physical state of a substance. But on the other hand, a chemical change is a process that results in the formation of a new substance. And that is correct. So B is our final answer to complete this example. I hope that this made sense and let us know if you have any questions.

What is the difference between a physical change and a chemical change?

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Key Concepts

Physical Change

Chemical Change

Indicators of Change