Question

what do these two changes have in common? milk going sour making paper from wood select all that apply. both are caused by heating. both are changes of state. both are chemical changes. both are only physical changes.

Explanation:

1. Analyze "milk going sour": Milk souring involves the growth of bacteria that produce lactic acid, changing the chemical composition of milk. This is a chemical change.
2. Analyze "making paper from wood": Converting wood to paper involves chemical processes (like breaking down lignin, cellulose modification) to transform the wood's structure into paper. This is also a chemical change.
3. Evaluate the options:

• "Both are caused by heating": Milk souring can occur at room temperature, and paper production isn't solely caused by heating. So this is incorrect.
• "Both are changes of state": Changes of state (like melting, freezing) involve physical state changes (solid - liquid - gas) without chemical composition change. These two processes involve chemical composition change, so this is incorrect.
• "Both are chemical changes": As analyzed, both milk souring and making paper from wood involve chemical reactions and new substances are formed. This is correct.
• "Both are only physical changes": Both involve chemical changes, not just physical. So this is incorrect.

Answer:

Both are chemical changes.