Question

Circle the less dense item wood or water steel or water helium or air oil or water

Answer 1

1) Wood

2) Water

3) Helium

4) Oil

Step-by-step explanation:

In order to compare the densities in each pairt, let's have a look at the values of the density for each substance/material.

1) Wood vs water

Density of wood is variable, between
`0.2 g/cm^3` and
`1.0 g/cm^2` depending on the type of wood, while density of water is
`1.0 g/cm^3`: therefore, wood is less dense than water.

2) Steel vs water

Density of steel is around
`8-9 g/cm^3`, while that of water is
`1.0 g/cm^3`, so water is less dense than steel

3) Helium or air

Helium density is (at standard temperature and pressure) around
`9\cdot 10^(-5) g/cm^3`, while the air density is about
`0.001 g/cm^3`, so helium is less dense than water.

4) Oil or water

Oil density is around
`0.93 g/cm^3`, while water is
`1.0 g/cm^3`, so oil is less dense than water.

We can also use another method to compare the densities, without knowing their exact value. In fact, a substance 1 which is less dense than a substance 2 will float in substance 2, otherwise it will sink.

From common experience, we know that:

- Wood floats in water, so wood is less dense than water

- Steel sinks in water, so water is less dense than steel

- Helium floats in air (a helium balloon goes up), so helium is less dense than water

- Oil floats in water, so oil is less dense than water