What Is Low Density?
Density is the term given to describe an object and the amount of matter packed into a certain amount of mass. Density is also used to describe the weight of an object. For instance, the weight of a rock is far greater than the weight of a Styrofoam ball. Even though the rock and the Styrofoam ball may have the same dimensions, the rock has more matter packed into its structure than the Styrofoam ball. This type of phenomenon is known as density.
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History
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The density of an object was first used to determine the authenticity of gold. The philosopher and mathematician, Archimedes, was tasked with finding false gold given to the king. Archimedes thought of the idea of density and its relation to water while bathing. He thought of his body floating in water, and envisioned the calculation and experimentation that is even used today.
Evaluating Low Density
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In science, the density of an object is measured relative to water. When the density of an object is low, it floats in water. Because water is used as a reference point, the density of water is measured as 1.00 g/mL. An example of a low density compound is oil, since it floats at the top of water when combined.
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Ice Phenomenon
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An interesting part of nature is the phenomenon of freezing water. Normally, when you freeze a liquid, its density increases because of its phase change from liquid to solid. The substance normally becomes smaller and the matter becomes more compact. This increases a liquid's density and makes it heavier. However, the phenomenon of water is opposite from all other natural elements. Freezing water makes it expand and it becomes less dense. Therefore, ice floats in water, whereas other molecules sink.
The Equation
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Part of discovering elements with low density is using an equation. The equation to calculate density is:
Density = mass / volume
This calculation gives a better understanding of why an object of a certain type of element will have a lower density than another object of the same element with a smaller mass. For instance, if you have hydrogen gas in a container, and you lower the volume of the container, the amount of matter (mass) remains the same, but the volume becomes smaller. As the volume in the denominator of the equation becomes smaller, density increases.
Density and Weight
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Density determines weight by its attraction to other objects of matter. This is exhibited using the common analogy of a man located on the moon. On earth (a planet with greater mass than the moon), a man may weigh 150 pounds. However, even though the density of the man is the same on the moon, the moon's mass is much lower than earth. The decrease in mass on the moon has a lower gravitational pull on the man, so his weight is much smaller.
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