Question

what do these two changes have in common?
snails growing shells
ice crystals forming on a window
select all that apply.
both are caused by cooling. both are caused by heatin
both conserve mass. both are changes of state

Explanation:

1. Analyze "snails growing shells": This is a biological growth process where the snail uses materials (like calcium) to build its shell. Mass is conserved as the materials are transformed, not created or destroyed. It's not a change of state (snail's shell growth is biological, not a phase change like solid - liquid - gas) and not caused by cooling or heating in the way phase changes are.
2. Analyze "ice crystals forming on a window": This is a physical change (freezing, a change of state from water vapor to solid ice). Mass is conserved (the mass of water vapor before freezing equals the mass of ice crystals after). It is caused by cooling (the window is cold, causing water vapor to freeze).
3. Now check the options:

• "Both are caused by cooling": Snail shell growth is not caused by cooling, so this is incorrect.
• "Both are caused by heating": Neither process is caused by heating (snail growth is biological, ice formation is cooling - induced), so this is incorrect.
• "Both conserve mass": According to the law of conservation of mass, in both the biological growth of the snail's shell (materials are rearranged) and the physical change of ice crystal formation (phase change, mass of water is conserved), mass is conserved. So this is correct.
• "Both are changes of state": Snail shell growth is a biological process, not a change of state (solid, liquid, gas change), while ice crystal formation is a change of state (gas to solid). So this is incorrect.

Answer:

Both conserve mass.