7.2 Fluids and Density

7.2 Fluids and Density

What are fluids?

A fluid is any form of matter that can flow.

Liquids and gases are fluids. (They are able to flow, because they do not have a fixed shape)
Solids are not fluids. (They have a fixed, rigid shape)

How does temperature affect density?

As energy is added to the air inside the balloon, the heated air gets less dense than the air outside the balloon.

his means that a substance gets less dense as energy is added to it.

Solid, liquid and gas density

Why are gases less dense than liquid?

Density is the mass of a given volume.
Density describes how closely packed together the particles are in a material.

You can find density of a substance if you know its mass and volume.
Measuring the volume a solid object depends on its shape.

Ex: a block (rectangular)
Multiply the length and by its width and by its height.
Ex: Length =4cm width= 3cm height= 2cm
Volume of a block= 4×3×2= 24

Displacement

If the object has an irregular shape, you can use a technique called displacement.

Displacement is the amount of space that an object takes up when it is placed in a fluid.
The amount of fluid that is displaced by an object is equal to the volume of the object.

Calculating Density

Once you know the mass and volume of a substance, you can calculate the density.

※ You can calculate both fluids and solids.

Density equals the mass of something divided by its volume.

The mass units for solids, liquids and gases are often grams (g) or kilograms (kg)

If the object is solid, the volume units are often cubic centimeters.

If the object is a fluid, the volume units are often milliliters (mL)