Circle the letter for all examples of chemical change. Circle all correct answers.

Question

Circle the letter for all examples of chemical change.  Circle all correct answers.

BlackTom AI · Accepted Answer

To determine which options depict a chemical change, we need to consider whether a new substance is formed, accompanied by a change in composition or chemical identity. 
Option 1: 'Burning of gasoline in your car' This is a combustion reaction where gasoline reacts with oxygen to form new substances such as carbon dioxide and water, releasing energy. This clearly represents a chemical change because the original fuel is transformed into entirely different compounds. 
Option 2: 'Adding HNO3 to Cu to produce NO2 gas' Here copper reacts with nitric acid to yield nitrogen dioxide gas and copper ions in solution, which involves breaking old bonds and forming new ones, i.e., a chemical transformation. This is another true chemical change. 
Option 3: 'Subliming NH4Cl' Sublimation involves a physical change where a solid transforms directly into a gas without passing through a liquid phase. No new substance is created, so this is not a chemical change. 
Option 4: 'Decanting a solution of NaCl from sand' Decanting separates components based on density but does not alter the chemical identities of NaCl or sand; it is a physical separation. There is no chemical reaction occurring, so this is not a chemical change. 
Overall, the first two options illustrate chemical changes, while the last two illustrate physical changes. Remember, chemical changes involve new substances and changes in chemical composition, whereas physical changes involve changes in state or physical separation without new substances forming.

Circle the letter for all examples of chemical change. Circle all correct answers.

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