Which of the following is an example of a chemical change (change in chemical composition) that involves starting with a liquid and ending up with a gas?
Burning gasoline (combustion).
Boiling acetone.
A pond evaporating.
Condensation of steam.
Burning of gasoline (combustion)
note that phase changes are physical changes only.
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Which of the following is an example of a chemical change?
A change in water from a solid to a liquid
A log burning over a fire Adding salt to a pot of water
Painting a fence brown
To determine which of the given options is an example of a chemical change that involves starting with a liquid and ending up with a gas, let's analyze each option:
1. Burning gasoline (combustion): This involves the chemical reaction of gasoline with oxygen, resulting in the formation of carbon dioxide and water vapor. While it does involve a change from a liquid to a gas, it is primarily a combustion reaction and not just a change in states.
2. Boiling acetone: Boiling is a physical change that occurs when a liquid reaches its boiling point and changes to a gas. It is not a chemical change as the composition of the substance remains the same. Thus, this option does not qualify.
3. A pond evaporating: This is a physical change where the liquid water from the pond is transformed into water vapor through the process of evaporation. Like boiling, it is not a chemical change since there is no change in the chemical composition of water.
4. Condensation of steam: Condensation is the opposite of evaporation. It is a physical change where water vapor (gas) cools down and becomes liquid water. While this process involves a change from a gas to a liquid, it is not a change in chemical composition.
Therefore, the correct answer is option 1: Burning gasoline (combustion). It involves the chemical reaction of gasoline transforming into carbon dioxide and water vapor, which is a chemical change that starts with a liquid and ends with a gas.