Question

what do these two changes have in common? building a tower out of magnetic blocks ice crystals forming on a window select all that apply. both are caused by cooling. both are changes of state. both are only physical changes. both conserve mass.

Explanation:

1. Building a tower with magnetic blocks: This is a physical change (arranging blocks, no new substance) and mass is conserved (mass of blocks remains). It's not caused by cooling or a state change (blocks are solid, tower is solid).
2. Ice crystals forming: This is a physical change (water to ice, state change - liquid to solid, caused by cooling) and mass is conserved (mass of water/ice remains).

Now, analyze each option:

• "Both are caused by cooling": Building the tower isn't caused by cooling. Eliminate.
• "Both are changes of state": Building the tower doesn't involve a state change. Eliminate.
• "Both are only physical changes": Both processes don't create new substances (tower is arrangement, ice is water's solid state). This applies.
• "Both conserve mass": In physical changes, mass is conserved (tower: blocks' mass same; ice: water's mass same). This applies.

Wait, initial check was wrong. Let's re - evaluate:

• Building a tower with magnetic blocks: Physical change (no chemical reaction), mass of blocks is conserved (mass before = mass after).
• Ice crystals forming: Physical change (state change, liquid to solid), mass of water is conserved (mass before = mass after).
• "Both are only physical changes": Correct, as both don't involve chemical reactions (tower is arrangement, ice is state change).
• "Both conserve mass": Correct, as physical changes conserve mass (Law of Conservation of Mass applies to physical changes too, as no matter is created or destroyed).

The options "Both are only physical changes" and "Both conserve mass" are correct. The options "Both are caused by cooling" (tower building isn't) and "Both are changes of state" (tower building isn't) are incorrect.

Answer:

Both are only physical changes, Both conserve mass