Answer the following questions based on the activity:
 
A group of students performed a simple experiment to observe the changes that occur when two substances are mixed.

They poured a small amount of vinegar into a test tube and added a pinch of baking soda. Immediately, they noticed vigorous bubbling and a fizzing sound. The gas produced was passed through another test tube containing fresh lime water, which turned milky.

The students recorded their observations and discussed whether the activity showed a physical or a chemical change.
 
1. Why was the gas passed through lime water?
 
2. Which statement correctly describes the carbon dioxide formed during the activity?