What defines how heavy an item is? e.g. WHY does a brick weigh more than a sponge?

Answer 1

A brick has a greater mass than a sponge. This is because it is denser. Density is basically how many molecules an item has for its size. So even though a sponge is the same size, it is lighter because it has far less molecules (most of it is air).

Answer 2

One item weighs more than another because it contains more or heavier atoms.

A brick has more atoms in it than a dry sponge of the same size would.

Well- OK, the sponge has a lot of air inside of it... maybe there are about as many atoms of the air gases as there are of the elements making up the brick.

That brings us to the weight of the atoms themselves. Each element has an 'atomic weight'- the weight of the atom. The lighter the atom, the lower the atomic weight (and the smaller the element's number).

Just for simplicity, we will use the elements of oxygen to represent air, and calcium to represent the brick. Each of these is actually made up of many different components- some lighter some heavier, but this is just a simplified example.

Oxygen's atomic weight is almost 16, while calcium's is 40- over twice as heavy. A million atoms of calcium will weigh over twice what a million atoms of oxygen will.

But... a brick weighs more than twice what a dry sponge of the same size would. That is because of the spacing of the atoms. Bricks are made by pounding materials together, driving out air space, shoving atoms closer together while sponges are designed to grow in a light and fluffy way that makes lots and lots of air spaces, spreading the atoms further apart.

(Again, this is simplified- but that's OK!)

So- to make something heavy, you add more atoms (change the 'density') and/or use heavier atoms (change the 'mass').

Answer 3

An item's mass defines how heavy it is. weight is the effect of gravity on an object.
If an object has a mass of 1 kilogram it will weigh approx 10 newtons.

a brick has a larger mass than a sponge because it contains more heavier molecules than a sponge.

Answer 4

It's ALL about density and volume.

A ton of bricks has the same mass as a ton of feathers. The key is the density of the substance. If you have a certain volume of bricks with an equal volume of feathers, the bricks will weigh more. The masses of the two different volumes are different because there is more matter within the same volume in the case of the bricks, hence, they will have more mass, if the volume is the same.

Answer 5

Are you're getting mass and density mixed up.

The sponge has a low density because it has less matter per unit volume and hence a sponge with the same volume as a brick has less matter and hence is lighter.

Answer 6

The number and density of the atoms. Weight is not a result of the amount of gravity pulling it down. It's the result of everything in the universe pushing it down towards the compression.

Answer 7

it depends on what the item is made of.

If it's made of molecules that contain more particles, then gravity will pull them towards the centre of the earth with a bigger force, therfore they will be heavier, or have a larger 'weight'.

Answer 8

density of the materials the item is made of;
higher density = greater weight

Answer 9

The effect of gravity on mass and density.

Answer 10

MAss and density