Question: Maria weighed a small, wet sponge. It weighed 38 grams. She left the sponge on the balance. The next day, Jose found the sponge on the balance. It weighed 22 grams. Both students weighed the sponge accurately. Why were the masses different?
Reference answer: Some water evaporated from the sponge between the time Maria weighed the sponge and the time Jose weighed the sponge.

Student answer: Their masses were different because the water on the sponge evaporated. If you leave water out for a certain period of time, it will evaporate.

Student answer: The mass was different because water evaporated from the sponge before they weighed it again so the weight changed.

Student answer: Well because the water probably evaporated 16 grams the day Maria weighed the sponge. When Jose weighed it, it was probably lighter.

Student answer: They were different because if you leave water out it will evaporate. Some of the water in the sponge evaporated.

Student answer: Because water is really strong and it could make a sponge heavier but when it dried, water was not on the sponge no more so that made it weigh lower.

Student answer: They were different because all of the water in the sponge evaporated and water is heavy so it made the sponge heavy but when it evaporated it made the sponge weigh lighter.

Student answer: Overnight the water in the sponge had evaporated so that sponge weighed less.

Student answer: Because over the hours the sponge evaporated.

Student answer: The masses were different because Maria probably left the balance by a heated source. If she had left it by a heated source, the wet sponge the water in it might have evaporated.

Student answer: Because when Maria weighed it, it had water in it and when Jose weighed it, the water had already evaporated.

Student answer: Because some of the water from the sponge evaporated.

Student answer: The water in the sponge evaporated.

Student answer: The sponge has water in it. The water evaporated and made the sponge not as heavy.

Student answer: That happened because when you leave something out it will get evaporated.

Student answer: Because it evaporated.

Student answer: The masses were different because the water on the sponge evaporated.

Student answer: The masses were different because some water evaporated.

Student answer: The masses were different because some of the water in the sponge had evaporated.

Student answer: Because overnight some of the water in the sponge evaporated.

Student answer: Water has evaporated from the sponge over the night, making the sponge less heavy.

Student answer: The masses were different because some of the water evaporated.

Student answer: The sponge evaporated some water.

Student answer: The masses were different because when Maria left it on the balance, the water evaporated and made the sponge lighter.

Student answer: The masses were different because within the next day some of the water evaporated out of the sponge, so now that it has lost some of its water, it weighs less.

Student answer: The masses were different because some of the water on the damp sponge evaporated.

Student answer: The mass was different because some water evaporated from the sponge and made it weigh less.

Student answer: Because maybe Maria put in more water than Jose.

Student answer: The masses were different because some water evaporated overnight.

Student answer: Because the sponge was evaporating to the air.

Student answer: Because some of the water on the towel evaporated.

Student answer: Because they both evaporated and lost weight.

Student answer: Because of evaporation from the sun.

Student answer: Because the sponge evaporated.

Student answer: Evaporation.

Student answer: The wind and the water.

Student answer: Because overnight, the water got warmer somehow.

Student answer: That must have been from evaporation. The water on the sponge probably evaporated.

Student answer: Because the sponge was left there all night, so most of the water from the sponge evaporated. Maria weighed the sponge when it was still very wet, but Jose weighed it when the water had already evaporated.

Student answer: Because the sponge evaporated.

Student answer: Maria let the sponge sit and water from the sponge evaporated and took water out of the sponge and turned it into water vapor so the sponge got lighter since it had less mass.

Student answer: Because the sponge dried when Maria left.

Student answer: The water on the sponge was evaporated, so Jose's sponge was lighter than Maria's.

Student answer: Because the water inside the sponge had partly evaporated.

Student answer: They were different because the first day the sponge was heavy with water, but the next day the water had evaporated, so it had lost weight since the day before.

Student answer: Because Jose wet it the day before he looked at it, so it evaporated.

Student answer: Because the water in the sponge evaporated.

Student answer: Because some of the water evaporated, making it turn into water vapor.

Student answer: The water evaporated. That made it weigh less.

Student answer: Because the next day the water in the sponge evaporated. If she put the sponge in a case, it would not evaporate fast.

Student answer: Because it evaporated so there is not more water in it. Water cause weight too.

Student answer: The water in the sponge evaporated the next day which made it lighter.

Student answer: Because the water from the sponge evaporated.

Student answer: Because some of the water in the sponge might have evaporated.

Student answer: Because some of the water evaporated from the sponge.

Student answer: The water in the wet sponge evaporated.

Student answer: It is called evaporation. It evaporated because it could have been in heat or the sun.

Student answer: Some of the water in the sponge evaporated.

Student answer: Maria weighed the sponge when it was wet. Then the water evaporated and Jose weighed it.

Student answer: Some of the water evaporated from the cup.

Student answer: They were different because the water caused the sponge to get heavy and the next day when Jose found the sponge some of the water on the sponge has evaporated.

Student answer: Because overnight the water in the sponge evaporated so there was no water and it weighed less.

Student answer: The sponge's water evaporated.

Student answer: Since it was a wet sponge, the water that was inside of it evaporated so it made it weigh less.

Student answer: Because the water in the sponge start to evaporate because some of the water gets hot and contracts to the less dense molecules. So then there is less water in the sponge.

Student answer: Because some water in the sponge evaporated and less water meant less weight.

Student answer: Because the water in the sponge evaporated, so a bit of weight went with it.

Student answer: Because some of the water evaporated. So that caused the weight of the sponge to decrease.

Student answer: Because some of the water from Maria's cup evaporated.

Student answer: Because it was getting dry easily because it evaporated.

Student answer: Because the water in the sponge evaporated.

Student answer: Because some of the water evaporated overnight.

Student answer: Because the water in the sponge evaporated overnight and that means it would not be as heavy.

Student answer: Because some of the water in the wet sponge evaporated.

Student answer: Well the sponge must have evaporated a little since the day before.

Student answer: Because the water evaporated in the sponge.

Student answer: Because the sponge soaks up the water in it.

Student answer: Because water does weigh something. If the sponge is wet one day the next it will be dryer, and weigh less.

Student answer: Because the water in the sponge evaporated.

Student answer: Because the water evaporated, and the sponge weighed its normal weight without water.

Student answer: Because most is closest of evaporation.

Student answer: Because if it was outside all the water dried up which made it weigh less. It weighed more with the water in.

Student answer: The water in the sponge evaporated so it weighed less because water weighs a certain amount.

Student answer: Because the water in the sponge evaporated overnight. Water is more dense than air. So when there was water in the sponge other than nothing but air in the sponge!

Student answer: The masses were different because part of the water evaporated.

Student answer: Because some of it evaporated into the air.

Student answer: Because when Maria weighed it was full of water but when Jose weighed it the sponge had dried.

Student answer: Water can weigh a substance down. When water from the sponge is evaporated, it gets lighter.

Student answer: Because of evaporation.

Student answer: Because of evaporation the water from the sponge evaporated into the Air!

Student answer: Overnight the water must have evaporated.

Student answer: The masses were different because some of the sponge's water evaporated overnight.

Student answer: Because it dried out it soaked up the water.

Student answer: Because some water evaporated overnight.

Student answer: Because overnight it probably soaked into the sponge.

Student answer: They used different sponges.

Student answer: Because some of the water evaporated from the sponge!

Student answer: Because some of the water might have evaporated into the sky. It might have turned into water vapor.

Student answer: Because some of the water evaporated and turned into water vapor.

Student answer: Because it evaporated the water.

Student answer: Because the water on the sponge was evaporated.