In this section, we take a look at physical sciences – which includes both chemistry and physics. You are only required to understand the basic principles of these two subjects, something we go into detail below.
Posted in 1st December, 2014 | General SciencePhysical Sciences
Physical Sciences
A considerable amount of questions on your exam will be devoted to the biology section, which explains why your requirements in the physical sciences are somewhat reduced. When we say physical sciences, what we’re really referring to is chemistry and physics. Thankfully, you are not expected to know these subjects in detail but are, instead, expected to be familiar with the fundamentals of these essential sciences. When you think about it, this should make sense, as many military careers involve some interaction with the principles of chemistry or the application of physics. In this section, we will go through what you are expected to know – detailing the relevant points along the way.
We will begin by looking at chemistry – more specifically at the elements and periodic table. From here, our attention will turn to various physical phenomena, particularly those in relation to simple calculations. Everything referred to in this study guide is examinable material on the ASVAB General Science test – try to become familiar with the topics before engaging with them in any depth, as this will break you in to the subject at hand. At the end of this study guide, you will find a self-assessment quiz which, in part, focuses on the material discussed here.
Basic Principles of Chemistry
We begin by glancing at everything – as it’s everything we can see that makes up matter. Matter, in other words, is the name given to everything that is made up of stuff. More specifically, this stuff is elements. Elements are what constitute matter, in the way that H2O is what constitutes water. When two molecules of hydrogen team up with one molecule of oxygen, we form water. This water can exist in three possible states – known as states of matter – gas, liquid, or solid. Water manifests in each of these three states depending on the temperature. When the temperature exceeds 212°F, the water molecules will separate thanks to the energy provided by the heat. This is what we see as steam.
At room temperature, the molecules of water are neither highly energetic (thanks to too much heat) nor non-energetic (as occurs when water freezes) – and so the molecules flow, which is what we see as regular water. The purpose here is to highlight the relationship that exists between temperature, elements, and molecules. Water is a molecule composed of two different types of element – hydrogen and oxygen. Everything we see around is, similarly, composed of different elements in different molecular structures – all constituting the overarching title of matter. When we say we are heating water, what we’re really saying is that we’re providing water with energy. The more energy, the greater the movement of molecules, and the higher the temperature will become.
- The state of matter with the greatest kinetic (moving) energy is the gas state.
- The state of matter with the least kinetic (moving) energy is the solid state.
Similarly, pressure also has an effect on temperature. Think about cooking a pot of vegetables. When we place the lid on the pot, the heat cannot escape. This heat is forced to remain and, consequently, the temperature of the contents will rise due to this extra pressure. The relationship between temperature, pressure, and elements is an important one, as it underlies many physical phenomena. When we talk about increased temperatures adding extra energy to molecules, what exactly do we mean? To answer this question, we need to turn our attention to the most fundamental structure of matter – the atom. By exploring the structure and function of the atom, we will have a greater understanding of the basic principles outlined above.
Explaining the Atom
So, what is the difference between an atom and an element? An element is not the fundamental state of nature because it can exist as a molecule. For instance, the element hydrogen is stable in the form H2 – what this means is that two atoms of hydrogen are necessary to form the stable element of the same name. An atom, therefore, is the fundamental building block of nature. Atoms are arranged in a certain distinct pattern. At the center of the atom we find the nucleus. Orbiting around the nucleus we find electrons. Electrons are negatively charged particles that orbit around the nucleus of an atom. When an atom loses an electron, it is known as an ion.
The nucleus is composed of two types of particle: neutron and proton. Protons are positively charged particles while neutrons have no charge at all. The number of protons present in the nucleus of an atom is known as its atomic number. So, for example, if a particular atom has eight protons in its nucleus, then the atomic number of that atom is also eight. These atoms can join up together to form molecules, or alternatively if the elements are different, it will be known as a compound. Water, for example, is a compound of hydrogen and oxygen. Hydrogen, in the form H2, is known as a molecule of hydrogen, or molecular hydrogen.
As you study equations, consider two important points – what each variable represents as well as the scientific units of these variables.
You should take some common household substances and analyze the elements present. Let’s take table salt, for example, which is a compound of Sodium and Chlorine (sodium chloride). Alternatively, we could think of gas varieties – where carbon dioxide is composed of one atom of carbon and two atoms of oxygen. When you see the prefix di-, you should be aware that it’s referring to ‘two of’ something. There are many types of element, and its important scientists know how to classify and categorize them. The periodic table of elements is used for these classification purposes. It is arranged based off atomic numbers, so the atom with 1 proton (hydrogen) appears first, while the atom with 2 protons (helium) appears second, and so on.
For your ASVAB General Science exam, you are expected to understand the structure of the periodic table.
- The rows of the table are referred to as periods.
- The columns of the table are referred to as groups.
- Group 17 elements are known as the Halogens; including the elements fluorine, chlorine, bromine and iodine.
- Group 18 elements are known as the Noble Gases; including the elements helium, neon, argon, krypton, xenon, and radon.
- Group 1 elements are known as the Alkali Metals, while Group 2 elements are known as the Alkaline Earth Metals.
When you look at any element on the periodic table, you will see three things. The top number refers to its atomic number i.e. the number of protons in the nucleus. Then, you will be presented with the chemical symbol for that element – so, for hydrogen, this presents as H. The bottom number is the atomic mass, which is the average mass for an atom of that element. We can see that sodium, Na, has an atomic mass of 22.9, while iron, Fe, has an atomic mass of 56 – clearly showing how iron is significantly heavier an element than sodium. You will need to become familiar with identifying these structures, as they regularly appear on the ASVAB General Science exam.
Playing with Physics
When it comes to discussing physics, we have already made great strides. The chemical principles outlined in the previous section are just as much physical principles. This means we can now focus on areas of pure physics. It’s also worth noting that physics is very much a mathematical subject, meaning you will need to become familiar with different types of equations. Don’t worry if you’re not particularly good at mathematics, as we will explain everything you need to know. In addition, you should always consider equations in terms of their context, which means becoming familiar with the theory behind the equation itself. We will look at several equations over the course of this section – and you should note the terms of the equation and what the equation aims to represent.
One of the first sections you should be familiar with is Einstein’s famous equation:
- E=MC^2
In this equation, E stands for energy, while M stands for mass and C stands for the speed of light. While it’s important you become familiar with these variables, you should also understand how the equation works. The equation is simple – if you multiply the speed of light (squared) by the mass of an object, you can determine the overall energy involved. Let’s think about this – if we increase the mass (M) of the object, what will happen? Inevitably, the energy will also rise. Think of M as 2 and C as 32, the answer E would work out as 2 + 9 = 11. If we increase the mass to 4, E is calculated as 13. The point is this – equations might look complex but they’re actually describing simple events. Let’s take a look at another common equation – how to calculate force.
- F = MA
In this case, F refers to force; M refers to mass, while A refers to acceleration. In essence, the force of something can be calculated if we know its mass and acceleration. Consequently, if we increase the mass we will also increase the force. If we decrease the mass we decrease the force. Always try to think of these equations in terms of simple numbers, before worrying about how they work on a more detailed level. What is acceleration? According to physics, acceleration is defined as the rate at which the velocity of an object changes over time. If an object did not increase its velocity at any time, then the acceleration is 0. But, if the velocity changes with time, then the concept of acceleration comes into play.
Force, mass, acceleration, and energy – all concepts you should be familiar with for your ASVAB General Science exam. Before we conclude this particular section, we need to take a closer look at that last variable in that list – energy. Energy is most commonly measured in terms of Joules. In other words, when scientists measure the amount of energy in something, they will refer to that amount in terms of Joules, in the same way yards are used as a unit of measure. However, from a conceptual perspective, there are different types of energy, depending on the way it’s found. If you take a peek at the list below, it will go through all the different forms of energy you are expected to know for the ASVAB test:
- Gravitational Energy – The energy from which objects are pulled toward a center of mass. The Earth, for example, is a center of mass and all objects on Earth feel the gravitational pull toward the center of this mass.
- Kinetic Energy – This is the energy of motion. As something travels around, it is using kinetic energy. In other words, it’s not storing any energy, but actively using it to some appreciable extent.
- Potential Energy – This is the opposite of kinetic energy and is, instead, the energy stored under a particular set of circumstances. If I were to, for example, extend an elastic band, the band would store potential energy and release this energy should I let the band go.
- Electrical Energy – This is the type of energy produced from the flow of electrons. As electrons flow around a substance (such as a conductor, like metal), they can generate an electric current which manifests as a distinct type of energy.
You could be asked on your ASVAB General Science test about these different forms, more particularly they might give you a sample scenario and ask you to name which energy is involved. We go through some of these examples in the sample quiz of this guide. Before we conclude this physical sciences section, we first need to take a closer look at a couple of calculations. In past ASVAB tests, candidates were asked to convert various variables of one form into another – such as temperature calculations. In addition, you will also need to become familiar with the metric system of doing things – as this is the internationally accepted way of standardizing science around the world.
Units, Conversions, and Temperature
In the United States, we always refer to Fahrenheit but, in science, there are three ways of dealing with temperature; the other two referring to Celsius and Kelvin. For your ASVAB General Science test, you will be expected to know the values in the following table and, more importantly, how to convert Celsius into Fahrenheit and vice versa. While your test will not be replete with questions in this area, you should nonetheless be familiar with its operation should you wish to score the best mark you can. The concept of Kelvin will probably be alien to many of you, but it’s quite simple to grasp.
Scientists have determined that the coldest temperature possible is -273.15K. At this temperature, scientist’s claim the movement of molecules would actually stop given it would stop energy movement itself. This is, obviously, quite extreme. So, they based a scale around this temperature, known as the Kelvin scale. It’s quite easy to remember, as the scale is valued in the same way as the Celsius scale – with a 100 difference between the point water freezes and water boils. Scientists tend to use the Kelvin scale quite regularly, and it’s used in areas such as measuring the temperature of the Sun, among other areas.
| # | Temperature Scale | Water Freezes | Water Boils |
|---|---|---|---|
| 01 | Fahrenheit | 32°F | 212°F |
| 02 | Celsius | 0°C | 100°C |
| 03 | Kelvin | 273.15K | 373.15K |
So, how does one go about converting Celsius to Fahrenheit?
- F = 9⁄5 C + 32
If we were asked to convert 50°C to Fahrenheit, we would only need to slot it into the equation. The best approach is to follow these steps:
- Multiply the temperature in Celsius by nine – always the first step!
- This is, obviously, 50°C x 9 = 450.
- Next step is to divide this number by five, as per the equation.
- This is, as you have expected, 450/5 = 90.
- The final step simply involves adding 32 to this number, meaning we arrive at 112°F.
It’s quite a simple mathematical conversion! The only problem you might have is remembering the equation, but this shouldn’t be too difficult if you practice enough temperatures. If you were given the Fahrenheit and asked to convert to Celsius, you would simply reverse this process. You would first eliminate the fraction by multiplying the F by 5, and then divide that temperature by 9. Instead of adding the 32, you would subtract the 32. All in all, this shouldn’t prove too difficult should you encounter it on the day of your ASVAB General Science exam.
This completes our study of the physical sciences. As you can see, the range and depth of topics is not the same as biology, as biology questions tend to appear more frequently than the physical sciences. Nonetheless, the subjects of chemistry and physics play a sufficiently notable role to prompt you to take heed of their importance. As with biology, much of the emphasis here is on memorization, though there are a couple of areas where real understanding helps a lot. Try to keep all the relevant definitions in mind, as it’s these definitions that tend to crop up from time to time. As well as this, take the time to understand how to convert Celsius to Fahrenheit, as it will be well worth the effort.
The next section takes a look at the Earth sciences – in particular looking at weather, astronomy, geology, and the atmosphere.
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