Final answer:
Mixing chocolate syrup into milk and an iceberg melting slowly are both physical changes because no new substances are formed and these processes are reversible.
Step-by-step explanation:
The commonality between mixing chocolate syrup into milk and an iceberg melting slowly is that both are physical changes. A physical change involves a change in the properties of a substance without changing its chemical identity. When we mix chocolate syrup into milk, we are combining two substances to create a mixture, but the chocolate and milk can still be separated, meaning no new substance is formed. The process is reversible. Similarly, when an iceberg melts, the ice turns into liquid water. This is a change of state from solid to liquid. The water can be refrozen, so again, it's reversible and no new substances are created in this transition.
Melting ice is a classic example of a physical change, in which the water changes form but maintains its composition of hydrogen and oxygen. Dissolving, like when chocolate syrup mixes with milk, is also a reversible physical change, as the syrup can be separated from the milk, and the chocolate's chemical composition remains unchanged.