Which of the following is an example of only a physical change?(1 point)
Responses
the green color of the Statue of Liberty
the green color of the Statue of Liberty
the smell of rotten eggs
the smell of rotten eggs
dry ice becoming vapor
dry ice becoming vapor
the creation of table salt
the creation of table salt
The example of a physical change in this list is dry ice becoming vapor.
To determine which of the following options is an example of only a physical change, let's understand what physical changes are. A physical change refers to a change in the physical properties of a substance without altering its composition or chemical identity.
1. The green color of the Statue of Liberty: The green color of the Statue of Liberty is an example of a physical property, specifically its appearance or color. However, the green color is due to a process called oxidation, which is a chemical change. Therefore, this example involves both physical and chemical changes.
2. The smell of rotten eggs: The smell of rotten eggs is caused by a compound called hydrogen sulfide. Although the odor may change our perception, it does not alter the chemical composition of the substance. Hence, it is an example of a physical change.
3. Dry ice becoming vapor: Dry ice is solid carbon dioxide (CO2) at a temperature of -78.5°C. When it comes into contact with warmer air, it undergoes a process called sublimation, where it transitions directly from a solid to a gaseous state without becoming a liquid. This change is purely physical since it does not involve any alteration in the chemical makeup of CO2, making it an example of a physical change.
4. The creation of table salt: The creation of table salt involves a chemical reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) to produce sodium chloride (NaCl), which is the common table salt. This process involves the formation of new substances with different chemical properties and is therefore an example of a chemical change.
Based on the explanations provided, the correct answer is "dry ice becoming vapor," as this is the only option that represents a purely physical change without any chemical alterations.