What do these two changes have in common? a penny tarnishing a dinosaur bone turning into rock over millions of years Select all that apply. Both are only physical changes. Both are caused by heating. Both are changes of state. Both are chemical changes.

## Step 1<br />The problem presents two scenarios: a penny tarnishing and a dinosaur bone turning into rock over millions of years. We need to identify the commonality between these two changes.<br /><br />## Step 2<br />The first scenario, a penny tarnishing, involves the reaction of copper in the penny with oxygen in the air to form copper oxide. This is a chemical change because new substances are formed as a result of the reaction.<br /><br />## Step 3<br />The second scenario, a dinosaur bone turning into rock over millions of years, is a process known as fossilization. This involves the replacement of the organic material in the bone with minerals from the surrounding environment. This is also a chemical change because the original bone material is chemically altered to form a new substance.<br /><br />## Step 4<br />By comparing the two scenarios, we can see that both involve the formation of new substances, which is a characteristic of chemical changes. Therefore, the commonality between these two changes is that they are both chemical changes.