Density is the mass of an object compared to its volume. It describes the heaviness of an item. Density can also refer to how tightly packed a material or molecule is. The density of an object depends on its composition, pressure and temperature. By knowing how density works, you can have a better idea about the physical properties of liquids, gases and other objects, and how they will react when exposed to a particular element or environment.
Warm air is less dense than cool air. Because it weighs less, warm air rises. An example of this principle is a hot air balloon floating in the sky. Hot air balloons have torches at their base. When the torch ignites, it heats the air inside the balloon. Because the air in the balloon is warmer than the air surrounding it, it floats. When the operator wants the balloon to lower, he reduces the intensity of the flame on the torch, which allows the air in the balloon to cool.
In most instances, when a liquid transforms into a solid state, its density increases. An exception to this is water. When water turns into ice, its volume increases and the density decreases because the hydrogen bonds change. This is the reason why icebergs float in the oceans and ice cubes float in a glass of water. As water turns into ice, the hydrogen molecules bond to more water molecules. The molecules grow further apart when as ice forms, causing water to expand in volume. The empty spaces that form within the ice fill with air and make it weigh less than liquid water.
Not all liquids have the same density. According to Elmhurst College, chemists compare the density of liquids and other objects to water. Oil is less dense than water. In nature, this is problematic when a tanker spills oil into the water. Instead of sinking to the bottom, the oil floats and contaminates surrounding wildlife. You can see how oil floats on water by making an oil-based salad dressing, like a vinaigrette. Because the vinegar and water have similar densities, they blend together when mixed. When you add oil to the mixture, it will always float to the top of the container, even after you shake or whisk the dressing.
Basic household ingredients like water, sugar and raw eggs offer insight as to how adding or modifying elements affects the density of an object. After filling a glass jar with 1 cup of plain water and placing an egg in the water, the egg will sink because it’s denser than the water. By mixing 7 tablespoons of sugar with 1 cup of water in a different jar, you’ll find that the raw egg floats because the sugar altered the density of the water. If you slowly pour regular water into the jar that has the sugar water and egg, the regular water will float above the sugar water as the egg remains suspended between the two.
