The density of Matter - exciting 3D animation video

Attention Getting Question:

What do pumpkins, pencils, and ping pong balls have in common? They all float in water. We can determine if matter sinks or floats by measuring the mass and volume of a substance.

Introduction:

Matter is anything that has mass and takes up space. There are three states, or forms, of matter: solids, liquids, and gases. Properties describe the characteristics of matter. Mass and volume are properties of matter than can be measured. Mass is the amount of matter in a substance. Volume is the amount of space matter takes up.

Subject:

What Is Density?
When thinking back to the pumpkins, pencils, and ping pong balls, we know that they can float because their density is less than that of water. Density is another property of matter. Density is the amount of mass in a given amount of volume. To calculate the density of a substance, divide the mass by the volume.

An Illustration of Density
Pretend you have two boxes that are identical. What if you filled the first box with cotton balls and the second box with marbles? You could say that the box with marbles is denser than the box with cotton balls.

To determine if a substance can float in water, the substance must have a density that is less than the density of water. The density of water is 1.0 g/cm3. If the density of the substance is greater than 1.0 g/cm3, then the substance will sink in water.

The Density of a Domino
Let’s find out if this domino will sink or float in water. First we must determine the mass of the domino. We can measure the mass on a balance. We can see that the mass of the domino is 18 g.

Now let’s measure the volume of the same domino. If a solid is a rectangular prism like this domino, then you measure the length, width, and height. Multiply all three to determine the volume. We can see the length of the domino is 5 cm, the width of the domino is 2.5 cm, and the height of the domino is 1 cm. The volume of the domino is 12.5 cm3.

Once the mass and volume are identified, you can determine the density of a substance. When we divide the mass of 18 g by the volume of 12.5 cm3, we get a density of 1.44 g/cm3. Since the density of the domino is more than the density of water, the domino will sink when placed in water. It’s important to know that this does not mean that all dominoes will sink. Different domino sets can be made out of different materials. The density of each particular type of domino would have to be determined in order to know if the dominoes in each set will sink or float.

Summary:

You can determine if a substance will sink or float by determining the density of matter. Density equals mass divided by volume. If the density of a substance is less than that of water, it will float. If the density of a substance is more than that of water, it will sink. Scientists use density to describe matter and you can, too.
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