In this lesson, we will discuss how physics and chemistry are considered to be the two main branches of physical science. We will also look at the overlap between physics and chemistry.
The Physical Sciences
You probably already have a good idea what a physical object is: stars, cans, water, rocks and baseballs are all physical objects. The physical sciences seek to observe and explain the behavior of physical objects. Everything that's not alive falls within the physical sciences. This is in contrast to the life sciences or social sciences, which deal with living things and people. This leaves a lot of ground to cover, so scientists break the physical sciences up into subfields.
There are many other physical sciences, such as geology, astronomy, and meteorology. However, all these sciences rely heavily on results from physics and chemistry. Therefore, we say that the study of the physical universe is generally broken into these two most fundamental areas. Let's go into more detail.
Physics deals with the laws of motion of physical objects. Put another way, a physicist is most interested in finding how a particular system changes in time. For example, if you throw a baseball through the air, a physicist would want to measure all the forces involved with the throw and be able to predict the path of the ball at each point in time after it left your hand. A physicist would also want to measure how air flowed past an airplane wing or water past the hull of a boat.
Physics is also interested in the fundamental pieces of matter and the nature of space-time. This may seem very abstract, and that's because the smallest pieces of the universe are very, very small. Physicists have found that matter is made up of atoms, which themselves are made of protons, neutrons, and electrons. It doesn't end there either, protons and neutrons are also made of smaller pieces called quarks.
Searching for the fundamental building blocks of matter is a difficult and ongoing task. To help increase their knowledge, scientists from many countries have come together to build large machines, like the Large Hadron Collider (LHC), that slam subatomic particles together at high speeds. It's a little like ramming together two cars and figuring out what they were made of by looking at the wreckage.
In the other direction, the movement of distant stars and galaxies can tell us how to think of space-time. Physicists don't really see space-time as empty, it's more like a very lightly curved surface. For example, physicists now know that a star's gravity can bend space-time and cause light to bend around it, allowing us to see objects that are behind the star. The same physics responsible for bending starlight is needed to accurately calculate the time sent from Global Positioning System (GPS) satellites to Earth, so this stuff is important!
Chemistry deals with the internal properties of matter and how one substance transforms into another. A chemist is most interested in how to create new chemicals from existing substances using heat, solvents, electricity, radiation, and other means. There are only a little over one hundred chemical elements on the periodic table, but they can be combined in a nearly infinite number of ways. For example, the same four elements - carbon, hydrogen, oxygen, and nitrogen - make up most of the living things on the planet.
A chemist would be interested in how baking soda (sodium bicarbonate) and vinegar (acetic acid and water) come together to release carbon dioxide. Another example would be the lead and sulfuric acid in a car battery and how electric charge can slowly transfer from one to the other.
Chemists are also interested in analyzing unknown compounds to discover their exact chemical composition. They use many scientific instruments, such as spectrometers that measure how light is transmitted through a chemical to gather information about chemicals. Another way to determine a chemical's composition is to perform a series of chemical reactions to see if it behaves in certain known ways.
Chemistry is also concerned about what matter is made of; however, most explanations of chemical reactions don't require anything smaller than atoms, in fact different types of atoms were first discovered and organized by chemists into the periodic table. Protons, neutrons, and electrons are often useful in acid-base chemistry and nuclear chemistry.
As with many sciences there are strong areas of overlap between physics and chemistry. The laws of physics underlie chemistry, and the attempt to connect the underlying theories of atomic models to explain chemistry can be studied by both physicists and chemists.
Most chemical systems are too complex to directly apply the laws of physics, and chemical systems themselves can be the subject of scientific experiments. Some chemical reactions actually oscillate between different chemicals for hours before stopping, and many physicists have worked on the laws of how this happens. Physicists and chemists have also been involved with studying the liquid crystals that make up LCD (liquid crystal display) screens in TVs and monitors.
Though there is overlap between them, physics concerns the movement of physical objects in time, while chemistry concerns the transformation of physical matter from one type to another. Both are concerned with what matter is made of, but generally, physics looks at this question on a much smaller scale.