Which of the following is NOT a possible sign of a chemical change? (1 point)
a change in state
a change in color
the release of a gas
the release of energy
To determine which of the options is NOT a possible sign of a chemical change, let's go through each option and understand its relation to chemical changes.
1. "A change in state": This refers to a substance transitioning from one state (such as solid, liquid, or gas) to another due to a change in temperature or pressure. While this can sometimes be an indicator of a chemical change, such as in the case of boiling or sublimation, it can also happen without any chemical reactions occurring. Therefore, a change in state can occur without a chemical change taking place.
2. "A change in color": This is often an observable sign of a chemical change. During a chemical reaction, the arrangement of atoms or molecules may change, leading to the absorption or emission of specific wavelengths of light, resulting in a change in color.
3. "The release of a gas": This is another common sign of a chemical change. When certain substances undergo a chemical reaction, they can release gases as a byproduct. Examples include the effervescence observed when baking soda and vinegar react to produce carbon dioxide gas.
4. "The release of energy": Energy release can also indicate a chemical change. Chemical reactions often involve the breaking and forming of chemical bonds, which releases or absorbs energy. Examples of energy release include combustion reactions, where a substance reacts with oxygen and releases heat and light.
Based on the explanations above, the option that is NOT a possible sign of a chemical change is "a change in state." While a change in state can sometimes accompany a chemical change, it can also occur without any chemical reactions taking place.