How does water stay in an upside down glass?

When you first turn the cup upside down, the pressure of the air inside the cup and the air pressure outside the cup are equal. The pressure of the air outside the cup is now greater than the pressure inside the cup and the card stays in place.

What is it called when water is over the top of a glass?

A meniscus is a curve in the surface of a molecular substance (water, of course) when it touches another material. With water, you can think of it as when water sticks to the inside of a glass.

Why does the water not spill out of the glass when it is turned over?

When we fill the glass with water, we notice right away that it can go over the brim of the glass without spilling. This is because of surface tension. This attraction causes the molecules to stick together and avoid spilling down the side of the glass like gravity would like them to.

How do you keep a jar of water upside down?

Hold the card in place as you turn the card and the jar upside down. Let go of the card. Surprisingly, the card remains attached to the lid of the upside-down jar. Carefully remove the card from the opening and the water mysteriously stays in the jar!

Why does water bulge above the rim of the glass?

Why it works: Surface tension allows the water to bulge over the limit of the rim of the glass. Surface tension is the tendency of water molecues to want to stick together until forced apart. The water bulge will grow until it over hangs the rim so much that gravity forces the molecules apart.

Why does water dip in the middle?

Also, the water extends the highest close to the sides of the tube, and dips down in the middle of the tube. This is because the water molecules are more strongly attracted to the sides of the tube than to each other. The curved surface of the water in the capillary tube is called the meniscus.

What keeps the water inside the glass?

There is another separate effect that helps keep the water in the glass. Water molecules have a strong attractive “cohesive” force between them due to the fact that each water molecule can make four hydrogen bonds with other water molecules. (This cohesive force is the origin of surface tension.)

Why did water enter the upside down can in the water?

When the water in the can is heated, it changes to steam. This steam fills the can, replacing most of the air that was inside of it. When the inverted can is placed in cold water, the steam condenses, leaving the can mostly empty, and thus with a very low pressure inside of it.