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Chapter 2: Problem 1

When an iron object rusts, its mass increases. When a match burns, its mass decreases. Do these observations violate the law of conservation of mass? Explain.

Short Answer

Expert verified
No, these observations do not violate the law of conservation of mass. When the iron object rusts, it absorbs oxygen from the air, causing an increase in its mass but the total mass of the system (iron and air) remains constant. When a match burns, it releases gases into the air, which may seem like a loss in mass, but if we consider the entire system (match and air), the total mass remains constant. Thus, the law of conservation of mass is not violated in both processes.

Step by step solution

01

Understand the rusting process

Rust is the common name for iron oxide, which is created when iron bonds with oxygen. In this process, iron (Fe) reacts with oxygen (O2) in the air to form iron(III)oxide (Fe2O3). Thus, this process is technically not just involving the iron object, but also the oxygen in the surrounding air.
02

Interpretation of Iron Rusting

This means, when an iron object rusts and its mass seems to increase, it does not violate the law of conservation of mass. Although the iron item itself gets heavier, the increased mass is 'borrowed' from the oxygen in the surrounding air, which decreases equivalently. So, in the overall system (iron plus air), the total mass remains conserved.
03

Understand the burning process

Now, let's consider the burning match. Burning is a chemical process in which a substance reacts with oxygen to produce heat, light, and new substances. The match here reacts with oxygen from the air, creating carbon dioxide, water vapor and ash.
04

Interpretation of Match Burning

When a match burns, it indeed loses mass because some of the substances produced in the reaction (carbon dioxide and water vapor) are gases that dissipate into the air. However, if we could 'trap' these gases and weigh them, together with the remaining ash, we'd find that their total mass equals the original mass of the match plus the oxygen it reacted with. Therefore, the principle of conservation of mass still holds.

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Most popular questions from this chapter

A particular silver solder (used in the electronics industry to join electrical components) is to have the atom ratio of \(5.00 \mathrm{Ag} / 4.00 \mathrm{Cu} / 1.00 \mathrm{Zn}\). What masses of the three metals must be melted together to prepare \(1.00 \mathrm{kg}\) of the solder?

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