Question

kelsey made a sand castle at the beach. she mixed 100 grams of seawater with 400 grams of sand to make a 500-gram mixture. she used the mixture to build a sand castle. when kelsey was done, her sand castle had a mass of 450 grams. some sand was stuck to her hands. which statement explains the change in mass? all of the sand and seawater kelsey started with is in the sand castle. the sand on her hands is from somewhere else on the beach. the sand was cool when it lay on the beach. then it warmed up in the sun, so it lost mass. the sand castle is made of sand and seawater. most of the sand and seawater is in the sand castle, but some of it is on kelseys hands.

Explanation:

• First option: Incorrect, as sand stuck to hands means not all is in the castle.
• Second option: Temperature change doesn't change mass (mass conservation), so this is wrong.
• Third option: The mixture was 500g, castle is 450g. Mass conservation implies some (sand) is on hands, so this explains the mass change.

Answer:

The sand castle is made of sand and seawater. Most of the sand and seawater is in the sand castle, but some of it is on Kelsey's hands.