Why thing float

But why? Everything is made of molecules. Molecules are very, very tiny. You can only see them with a special microscope. In some objects, like a rock, molecules are squished tightly together.

In others, like wood, the molecules are more spread out. How closely molecules are crowded together in a space is called density. Objects like coins, rocks, and marbles are more dense than water. They will sink. For 6 Resources. Curated resources with practical work that students can complete at home, or that teachers can use when giving demonstrations Remote teaching support One piece of foil will sink and the other will float.

The piece of foil scrunched above water traps some of the air, which Enrichment Activity Food colouring and oil don't mix, and as the two separate the food colouring sinks into the water, leaving trails of colours. Other resources on Density Density Properties of Matter. Density Properties of Matter. Misconceptions Properties of Matter Some students think that heavy objects sink and light object float regardless of shape and size Number of Resources 0 Number of References 2 Number of Diagnostic Resources 2.

We've won an award! Learn more. Objects with tightly packed molecules are more dense than those where the molecules are spread out. Density plays a part in why some things float and some sink. Objects that are more dense than water sink and those less dense float. Hollow things often float too as air is less dense than water. This is partly why huge heavy ships float. Another thing to consider is the shape of an object. Generally the more of the outside of an object that is touching the water the more buoyant it is.

Water pushes back up against objects so the more surface area an object has the more water pushes back against it helping it to float. When an object floats, it pushes water out of the way displacement. Have you ever noticed that when you climb into a bath the water level rises? This easy activity demonstrates how reducing the density of a heavy object allows it to float. Place the bubble wrapped ball on the surface of the water, you should find it now floats.

Although the bubble wrap makes the ball weigh a little more, it also displaces extra water making the ball more buoyant. The pockets of air in the bubble wrap mean that the ball and bubble wrap together are less dense than the water, which means the ball floats!