Physical Science
The study of non‐living things and systems is known as physical science. It comprises studying the earth's minerals and physical properties, and elements found on earth. Physical science deals with matter at its microscopic levels and seeing how elements react with each other to make up certain substances. Apart from that, energy, force and motion are all discussed under physical science as these theories are what govern many of the physical properties of the objects studied by physical science.
Buoyancy
Buoyancy, as discussed earlier in the book is the force that keeps objects afloat in a body of liquid. Remember that all objects that float are able to do so because they are buoyed up by a force equal to the weight of the displaced liquid. This means that when you swim, you float because the amount of water you are displacing equals your weight, and so it keeps you floating and above water.
There are three types of buoyancy. The first type, positive buoyancy is an object that can float. The second type of buoyancy, neutral buoyancy is an object that neither floats nor sinks, which means it doesn't displace enough water to be pushed upward, but it displaces enough not to sink. It stays stable in the water, like fish. The final type of buoyancy is negative buoyancy. This is when an object does not displace enough water to keep it afloat or stable and so it sinks to the bottom of the water container.
The ability for something to float or be buoyant is discussed under physical science. You can determine whether something will float or not by determining the density of the fluid and the density of the object. If the object is denser than the fluid it displaces, then it will not float. The only way an object that is denser than the fluid it displaces will float is if it holds a pocket of air in it, like ships or submarines. This air pocket has a volume that is less dense than water, making the entire vessel's density less than water, and therefore able to float.
Knowing the density of an object is very useful in modern science. Not only does it help determine what floats, but it also aids in purifying metal and in other scientific advances we've seen in this century. For example, sending men on a rocket to the moon could not have been done without calculating the density of the materials that went into making the space ship.
The formula for density uses simple mathematics or basic division. To calculate for density, you divide the object's mass by its volume. It is easiest to use the kilograms over liter or grams over milliliters as your measurements for mass and volume. These are measurements your children will be introduced to in the first grade. And if you keep the numbers low, they can easily calculate for density.
Next Article: What Floats?
