Question

what do these two changes have in common? sanding a piece of wood a crayon melting in the sun select all that apply. both are only physical changes. both are chemical changes. both are caused by heating. both are caused by cooling.

Explanation:

• Physical vs. Chemical Changes:
• A physical change alters the form or appearance of a substance without changing its chemical composition. Sanding wood changes its shape and texture, and melting a crayon changes its state (from solid to liquid). In both cases, the substances (wood and crayon material) remain chemically the same.
• A chemical change results in the formation of new substances. Since no new substances are formed in sanding wood or melting a crayon, they are not chemical changes.
• Cause of Changes:
• Sanding wood is a mechanical process (using sandpaper to rub against the wood). Melting a crayon is caused by heat from the sun. So, they are not both caused by heating (only the crayon melting is heat - related in the traditional sense of adding thermal energy, and sanding is a mechanical cause, not a heating - in - the - sense of adding thermal energy for a chemical reaction). And clearly, neither is caused by cooling.

Answer:

A. Both are only physical changes.