Question

what do these two changes have in common? dust settling out of the air your breath becoming visible on a cold day select all that apply. both are changes of state. both are caused by heating. both are only physical changes. both are chemical changes.

Explanation:

1. Analyze "dust settling out of the air": Dust settling is a physical process where particles move due to gravity; no new substance is formed, and it's not a change of state (dust is solid, air is gas, settling is just movement). It's caused by gravity, not heating.
2. Analyze "breath becoming visible on a cold day": Breath (water vapor, gas) condenses to liquid droplets (change of state: gas to liquid). This is a physical change (no new substance, just state change) and is caused by cooling (not heating).
3. Evaluate options:

• "Both are changes of state": Dust settling is not a state change, so wrong.
• "Both are caused by heating": Both are caused by cooling/gravity, not heating, wrong.
• "Both are only physical changes": Dust settling (physical, no new substance) and breath condensation (physical, state change, no new substance) are both physical changes. Correct.
• "Both are chemical changes": Neither involves new substance formation, so wrong.

Answer:

Both are only physical changes.