Maya stirs a spoonful of sugar into warm water until she can no longer see any sugar. She tastes the water and it is sweet. What does the sweet taste show about the sugar?

A class leaves a shallow dish of salt water on a sunny windowsill. After several days there is no liquid left, but a white solid coats the bottom of the dish. Where did that solid come from?

A student seals the tip of a syringe that holds air, then pushes the plunger in. The air now takes up less space, and the plunger springs back when released. What best explains this?

When sugar dissolves completely in water, the sugar is still matter and still has weight.

A basketball feels soft. Each time it is pumped, the ball feels firmer, but its size barely changes. What is happening inside the ball?

A student crushes a sugar crystal into a fine powder. Even the smallest speck of that powder she can pick up still tastes sweet. What does this show about sugar?

A sealed jar of water sits on a balance and reads 250 grams. A student adds 20 grams of sugar, seals the jar again, and shakes it until no sugar can be seen. What does the balance read now?

Sand mixed in water is poured through filter paper, and the sand stays on the paper. Sugar water is poured through the same kind of filter, and the liquid that drips out still tastes sweet. Why?

A student caps the tip of a syringe that looks empty and pushes the plunger in partway. The plunger presses back on her hand and springs out again when she lets go. What does this show?

On a warm afternoon a puddle of salty ocean water on the sidewalk slowly shrinks. By evening the puddle is gone and a thin white ring is left on the pavement. What happened to the water?

A student stirs sugar into a tall pitcher of water until no sugar can be seen. She pours one cup from the top of the pitcher and one cup from the very bottom. Both cups taste equally sweet. What does this show about the sugar?

A ball pumped full of air weighs a little more than the same ball when it is flat.

A cup of salt water is left uncovered on a warm shelf. After two days about half of the liquid is gone, and the water still in the cup tastes much saltier than it did at the start. Why does it taste saltier?

A student opens a bottle of perfume at the front of the classroom. A minute later, students at the back can smell it, even though no one can see anything moving through the air. What does this show?

A jar of salt water is covered with a lid and set in the sun. Hours later, clear drops are hanging from the underside of the lid. What formed those drops?

A student wants to get solid salt back from a cup of salt water without adding anything to it. What method will work?

A student dips a spoon into a glass of clear sugar water and shakes a few drops onto a warm plate. Later the drops are gone and a sticky white speck is left where each drop had been. What does the speck show?

When salt water in an open dish dries up in the sun, the salt evaporates into the air along with the water.

One sealed syringe is full of water and another is full of air. Pushing the plunger moves it far in on the air syringe but almost not at all on the water syringe. What does this show?

A student argues that the air in a dry-looking room has no water in it at all. What evidence best shows the student is wrong?