Question

What do these two changes have in common?

sauce burning on a stove
making jam

Select all that apply.

A. Both are only physical changes

B. Both are chemical changes

C. Both are caused by heating

D. Both are caused by cooling

Answer 1

Both changes in question are physical changes, involving alterations in state or appearance without changing the substance's chemical identity. One is caused by cooling, and the other is a mechanical change without any alteration in the chemical composition.

Step-by-step explanation:

The commonality between the two changes mentioned is that both are examples of physical changes. A physical change is characterized by the alteration of the state or appearance of matter without changing its chemical identity. For instance, when water vapor condenses and freezes into snow, the water molecules rearrange but their chemical structure as H2O remains unchanged, exemplifying a physical change due to cooling. Another example is cutting hair; the hair’s structure is merely shortened, its chemical makeup remains the same, indicating a physical alteration.

It is essential to discern that these changes differ greatly from chemical changes, where new substances with different chemical compositions are formed, such as when making bread or burning coal. These transformations result from chemical reactions where the molecular bonds are broken and new ones are established, unlike physical changes where the form or phase changes but the substance's molecules stay intact.