What do these two changes have in common? an old sandwich rotting in a trashcan burning a marshmallow over a campfire Select all that apply. Both are only physical changes. Both are chemical changes. Both are caused by heating. Both are caused by cooling.

## Step 1<br />The problem involves understanding the nature of the changes that occur in two different scenarios: an old sandwich rotting in a trashcan and burning a marshmallow over a campfire. <br /><br />## Step 2<br />The first scenario involves an old sandwich rotting in a trashcan. This is a chemical change because the sandwich undergoes a process called decomposition. In this process, the complex molecules in the sandwich are broken down into simpler substances. This change is not reversible, which is a characteristic of a chemical change.<br /><br />## Step 3<br />The second scenario involves burning a marshmallow over a campfire. This is also a chemical change. When the marshmallow is burned, the heat causes the sugar in the marshmallow to break down into carbon and water vapor. This is a chemical change because the sugar molecules are chemically altered to form new substances.<br /><br />## Step 4<br />From the above analysis, we can see that both scenarios involve chemical changes. The changes are not caused by heating or cooling, but by the action of bacteria in the case of the rotting sandwich and by the heat of the campfire in the case of the burning marshmallow.