Question

lavoisier heated a piece of tin on a floating block of wood covered by a glass jar. As the tin decomposed, the water level inside the jar rose. How did Lavoisier explain this result?

Short answer

Lavoisier explained the rise as a result of oxygen being consumed, proving gases have mass.

Step-by-step solution

Understand the Setup

Recognize that Lavoisier's experiment involves a piece of tin being heated on a floating block of wood, covered by a glass jar, causing water level changes.

Identify the Process Happening

Understand that heating tin results in a chemical reaction where the tin reacts with oxygen in the air, forming tin oxide.

Chemical Reaction and Product Formation

When tin reacts with oxygen, it forms tin oxide, a solid that does not escape into the air, unlike the gaseous reactant, oxygen.

Explain the Rise in Water Level

As oxygen from the enclosed air combines with tin to form a solid, the volume of gas inside the jar decreases, leading to a partial vacuum.

Understand the Physical Result

The decrease in gas volume inside the jar causes the water level to rise inside the jar to fill the created space by the partial vacuum.

Lavoisier's Explanation

Lavoisier explained the rise in water level as the result of the oxygen gas being consumed in a chemical reaction, proving that gases have mass and take up space.

Key concepts

Chemical Reaction

In Lavoisier's experiment, a fundamental concept is the chemical reaction that occurs when tin is heated. A chemical reaction involves the transformation of substances through the rearrangement of atoms. Here, tin undergoes a specific reaction when it is exposed to heat in the presence of oxygen. This process is characterized by the breakdown of the tin and its combination with oxygen to form a new compound, known as tin oxide. The transformation can be mathematically expressed as:\[ \text{Sn} + \text{O}_2 \rightarrow \text{SnO}_2 \]In this equation, "Sn" represents tin, "O\(_2\)" is oxygen, and "SnO\(_2\)" is tin oxide. Such a reaction is a prime example of oxidation—a chemical process that involves the gain of oxygen or the loss of electrons.

Oxygen Consumption

A key part of the chemical process in Lavoisier's experiment is the consumption of oxygen. When the tin is heated, it attracts oxygen molecules from the air inside the jar. This reaction is not just a surface phenomenon; the oxygen binds chemically with the tin at an atomic level to form tin oxide. This consumption of oxygen is crucial because:

• It demonstrates that oxygen is a reactive agent that combines with other substances.
• It provides evidence that gases like oxygen have mass and significant chemical roles in reactions.

The consumption of oxygen in the reaction is what ultimately leads to observable changes in the experiment, like the drop in air pressure and volume inside the jar, hinting at its absence.

Gas Volume

As oxygen is utilized in forming tin oxide, there's a crucial shift in the gas volume within the glass jar. Initially, the jar contains a certain volume of air, which includes oxygen gas. However, during the reaction, oxygen molecules combine with tin, removing them from the gaseous phase and turning them into part of a solid compound. This change results in:

• A decrease in the overall gas volume inside the jar due to oxygen consumption.
• The creation of partial vacuum, owing to the reduced pressure inside the jar.

Since gases take up space, when the gas volume diminishes, the water level rises to fill the space created by the void, an ingenious method of visualizing and understanding changes in gas volume.

Tin Oxide

The formation of tin oxide is the main outcome of the chemical reaction in Lavoisier’s experiment. When tin comes into contact with oxygen during heating, the result is a transformation into tin oxide, a solid compound. Some important points about tin oxide include:

• Tin oxide itself is a stable compound that remains in the jar as a solid.
• It does not revert back to its original components, showcasing the permanence of chemical changes.

Tin oxide, thus, serves as a visible proof of the chemical reaction that took place. It underscores Lavoisier's revolutionary concept that matter is neither created nor destroyed but simply changes form, which forms the basis of the law of conservation of mass.