Which of the following is an example of only a physical change?
the smell of rotten eggs
the green color of the statue of liberty
dry ice becoming vapor
the creation of table salt
dry ice becoming vapor
which of the following example demonstrates the reversibility of a chemical change?
refreezing carbon dioxide gas into dry ice
the rotting of eggs
recharging batteries
dehydrating sugar water
refreezing carbon dioxide gas into dry ice
The example of only a physical change among the options given is "dry ice becoming vapor."
To determine which of the following options is an example of only a physical change, let's first understand what a physical change is. A physical change refers to a change that alters the physical characteristics of a substance without changing its chemical composition. In other words, the substance remains the same at a molecular level.
Now, let's examine each option and identify if it corresponds to a physical change:
1. The smell of rotten eggs: This is an example of a chemical change. When eggs rot, certain compounds break down, leading to the release of hydrogen sulfide gas, which produces the characteristic unpleasant scent. Chemical changes involve a rearrangement of atoms and a modification of the substance's chemical properties.
2. The green color of the Statue of Liberty: This is also an example of a chemical change. Over time, the copper surface of the statue reacts with air and moisture, forming a layer of copper oxide known as patina. This chemical reaction alters the composition of the copper, resulting in the green color. Again, a chemical change has occurred.
3. Dry ice becoming vapor: This is an example of a physical change. Dry ice is solid carbon dioxide, and when it sublimes, it directly transitions from a solid to a gas without going through a liquid phase. The dry ice molecules rearrange themselves, but the substance remains carbon dioxide, only changing its physical state from solid to gas.
4. The creation of table salt: This is an example of a chemical change. Table salt, or sodium chloride, is formed through a chemical reaction between sodium and chlorine. The atoms rearrange themselves and form a new compound with different properties than the individual elements.
Therefore, among the given options, the example of only a physical change is "dry ice becoming vapor."