Chapter+4

=Matter is the Stuff Around You= Matter is everything around you. **Matter** is anything made of [|atoms] and molecules. Matter is anything that has a **mass**. Matter is also related to light and electromagnetic radiation. Even though matter can be found all over the universe, you usually find it in just a few forms. As of 1995, scientists have identified five **states of matter**. They may discover one more by the time you get old.

You should know about solids, liquids, gases, plasmas, and a new one called Bose-Einstein condensates. The first four have been around a long time. The scientists who worked with the [|Bose-Einstein condensate] received a Nobel Prize for their work in 1995. But what makes a state of matter? It's about the physical state of molecules and atoms.

=Changing States of Matter= [|Elements] and compounds can move from one [|physical state] to another and not change. Oxygen (O2) as a gas still has the same properties as liquid oxygen. The [|liquid] state is colder and denser but the molecules are still the same. Water is another example. The **compound** water is made up of two hydrogen (H) atoms and one oxygen (O) atom. It has the same molecular structure whether it is a [|gas], liquid, or [|solid]. Although its physical state may change, its chemical state remains the same.

So you ask, "What is a chemical state?" If the formula of water were to change, that would be a **chemical change**. If you added another oxygen atom, you would make hydrogen peroxide (H2O2). Its molecules would not be water anymore. Changing states of matter is about changing densities, pressures, temperatures, and other physical properties. The basic chemical structure does not change.

=What Is a Mixture?=

A mixture is the blending of two or more dissimilar substances. A major characteristic of mixtures is that the materials do not chemically combine. Mixtures can be divided into those that are evenly distributed (**homogeneous**) and those that aren't (**heterogeneous**). The types of mixtures are a suspension, colloid or solution. Examples of mixtures include various combinations of solids, liquids and gases. Separation of mixtures can be by mechanical means, such as by weight, evaporation or other methods. Questions you may have include:
 * What are characteristics of mixtures?
 * What are examples of simple mixtures?
 * How do mixtures separate?

Mixture characteristics
A mixture is a combination of two or more materials, compounds or elements where there is no chemical combination or reaction. There are two ways material is distributed throughout a mixture. There are also three types of mixtures.

Comparing mixtures with compounds
Mixtures are quite different than chemical compounds.

//**Proportions**//
Mixtures combine physically in no definite proportions. They just mix. On the other hand, in a compound the substances combine chemically, forming molecules. The elements in a compound unite in definite proportions. For example, in the water molecule (**H2O**), there are always two parts Hydrogen and one part Oxygen.

//**No new substances**//
When you create a mixture, there are no new substances formed. Each part of a mixture retains its own properties. When a compound is formed, it is a new substance with new properties. You could mix various proportions of Hydrogen and Oxygen gas. As long as you did not ignite the mixture with a match so that it would explode in a chemical reaction, the combination would form a mixture that could be separated by the different weights of the gases. Each gas would retain its own properties.

//**Separation**//
The parts of a compound can be separated only by chemical means, while a mixture can be separated by physical means and not chemical means.

Distribution of material
The distribution of the materials in a mixture can be heterogeneous or homogeneous. Heterogeneous mixtures are those where the substances are not distributed evenly. They usually involve a mixture of a solid in a solid. A mixture of stones in soil is an example of a heterogeneous mixture. Homogeneous mixtures are those where the materials are evenly distributed throughout.

Types of mixtures
Mixtures can be classified into three types: suspension, colloidal and solution. Some fluid mixtures are solutions.

Suspension mixtures have larger particles and are heterogeneous. Most mixtures are suspension mixtures.
 * Suspension **

**Colloidal**
Colloidal mixtures fall between suspension and solution mixtures. The ingredients in colloidal mixtures are smaller and usually homogeneous. Homogenized milk is a colloidal mixture of cream and butterfat particles in skim milk. From its name, you can assume the particles are homogeneously distributed.

**Solutions**
Solutions are homogeneous mixtures that consist of microscopic particles and even molecules. The solute and solvent in a solution are either both polar or non-polar molecules, under normal conditions. Vinegar is a homogeneous mixture or solution of water and acetic acid. Salt water is another example of a solution.

Mixture examples
Simple mixtures can involve various combinations of solids, liquids and gases.

Solid in solid
Sand is an example of a suspension mixture of solid particles. By sifting the sand, you can separate particles according to size.

Solid in liquid
Muddy water is an example of solid particles mixed in a liquid. Dirt is added to the water and made into a mixture by stirring the ingredients. After a while, gravity will cause the particles to settle to the bottom. Blood is another example of solid particles in a liquid. The blood cells can be separated with a centrifuge.

Solid in gas
Smoke is an example of solid particles mixed in a gas. The solute smoke particles are added to the solvent air and mixed by convection currents. After a while, the particles will settle to the ground. Solid particles in the air are a major part of air pollution.

Liquid in liquid
If you thoroughly mix the solute oil and the solvent water, breaking the liquids into small globules, the mixture will soon separate. Oil and water do not mix on a permanent basis. Note that you could also mix the water in some oil. In that case, the water would be considered the solute and the oil the solvent.

**Homogenized milk**
Standard milk will soon separate into skim milk with cream at the top. By extreme mixing of the combination, they do not readily separate. This is called homogenized milk. Although it is not supposed to separate, it is not a real solution, because after a very long time, the cream will rise to the top. But by then, the milk has most likely gone bad.

Liquid in gas
Liquid particles can mix in a gas but will soon separate out. An example is a fine mist spray of water particles in air.

Gas in liquid
Bubbles of air or a gas can be seen in a liquid. Being lighter, they soon rise to the top.

Gas in gas
Gases mix at a molecule level. Air is a homogeneous mixture of Oxygen molecules, Nitrogen, Carbon Dioxide and some other gases. By the very nature of gases being in constant motion, so the heavier molecules seldom settle. There have been cases where a large amount of Carbon Dioxide gas was naturally discharged and did not immediately mix with the air, but instead settled in a low area for a while. This happened some years ago to a village in Africa, suffocating all the people and animals. By the time authorities came to the village, the **CO2** had been absorbed into the atmosphere. It took scientists to figure out how the people died.

Separation
You can separate a simple mixture by physical or mechanical means.

By weight
In many cases, the difference in weight of the substances will allow the effect of gravity to separate them. A centrifuge will accelerate the effect of gravity by using centrifugal force to separate the materials. It is possible to separate the milk and cream particles (or cream globules) by spinning the liquid in a centrifuge. Hospitals use the centrifuge to separate blood cells from the plasma, which can be preserved longer.

Evaporation
Changing a liquid into a gas can often separate liquid mixtures. This can be done by natural evaporation or by boiling the liquid mixture. This is often done in separating salt-water solutions.

Other methods
There are other miscellaneous methods to separate simple mixtures.

**Sifting**
Sifting materials of different sizes can separate some mixtures.

**Magnetism**
If you had a mixture of iron filings and some non-magnetic material, you could use a magnet to separate the mixture.

Summary
A simple mixture consists of substances that do not react chemically and can be separated by mechanical means, while in a compound the substances react and combine chemically. Mixtures can be heterogeneous or homogeneous. The types of mixtures are a suspension, colloid or solution. Combinations of solid, liquid or gas can be involved in a mixture. Gravity, boiling and sifting are some methods to separate mixtures.

=Pure Substances, Mixtures, and Separations=

The Basics of Separation
One way scientists talk about matter or substance—that is, the stuff in the world—is in terms of //pure substances// and //mixtures//. //Pure substances// are substances that contain only one kind of molecule. Water with nothing else in it is a pure substance. This is because it contains nothing but water molecules. On the other hand, suppose we put a teaspoon of sugar in a glass of water and let it dissolve. Now we have a glass full of mostly water molecules with some sugar molecules here and there between the water molecules. So our sugar-water isn’t a pure substance. It consists of more than one kind of molecule; thus it is a //mixture//.

Separation in the Real World
Mixtures are all around us, and most of the things you can touch or feel are mixtures, not pure substances. A lot of times this isn’t a problem. Orange juice is a mixture of water, sugar, vitamin C, citric acid, and more, and it’s perfectly fine as a mixture. But sometimes we need to separate the different substances in a mixture. For example, milk is a mixture of water, sugar, fat, protein, vitamins, calcium, and more. Calcium and protein are two things your body needs, but fat, while good for growing children, can be unhealthy for adults. To make a healthier milk for adults, we //separate// most of the fat from the milk, creating low-fat or “skim” milk. Crude oil (petroleum) is a mixture of all kinds of substances. Some of the substances are used to make gasoline and other fuels. Others are used to make plastics. Still others are used to make medicines. It takes a lot of work to separate all these substances in crude oil from each other. This is done in giant factories called refineries.

Whether we’re talking about milk or crude oil, //**separation of mixtures**// is very important in our world.

=ATOMS= BUILDING BLOCKS= Atoms are the basis of chemistry. They are the basis for everything in the Universe. You should start by remembering that matter is composed of atoms. Atoms and the study of atoms are a world unto themselves. We're going to cover basics like atomic structure and bonding between atoms. As you learn more, you can move to the biochemistry tutorials and see how atoms form compounds that help the biological world survive.

=SMALLER THAN ATOMS?= Are there pieces of matter that are smaller than atoms? Sure there are. You'll soon be learning that atoms are composed of pieces like neutrons, electrons, and protons. But guess what? There are even smaller particles moving around in atoms. These super-small particles can be found inside the protons and neutrons. Scientists have many names for those pieces, but you may have heard of **nucleons** and **quarks**. Nuclear chemists and physicists work together with particle accelerators to discover the presence of these tiny, tiny, tiny pieces of matter.

Even though those super tiny atomic particles exist, there are three basic parts of an atom. The parts are the **electrons**, **protons**, and **neutrons**. What are electrons, protons, and neutrons? A picture works best. You have a basic atom. There are three pieces to an atom. There are electrons, protons, and neutrons. That's all you have to remember. Three things! As you know, there are over 100 elements in the **periodic table**. The thing that makes each of those elements different is the number of electrons, protons, and neutrons. The protons and neutrons are always in the center of the atom. Scientists call the center of the atom the **nucleus**. The electrons are always found whizzing around the center in areas called orbitals.

You can also see that each piece has either a "+", "-", or a "0." That symbol refers to the charge of the particle. You know when you get a shock from a socket, static electricity, or lightning? Those are all different types of electric charges. There are even charges in tiny particles of matter like atoms. The electron always has a "-" or negative charge. The proton always has a "+" or positive charge. If the charge of an entire atom is "0", that means there are equal numbers of positive and negative pieces, equal numbers of electrons and protons. The third particle is the neutron. It has a neutral charge (a charge of zero). =LOOKING AT IONS= We've talked about ions before. Now it's time to get down to basics. Ions are atoms with either extra electrons or missing electrons. A normal atom is called a neutral atom. That term describes an atom with a number of electrons equal to the **atomic number**.

What do you do if you are a sodium (Na) atom? You have eleven electrons, one too many to have your shell filled. You need to find another element who will take that electron away from you. Bring in chlorine (Cl). Chlorine (Cl) will take that electron away and leave you with 10 electrons inside of two filled shells. You are a happy atom. Now you are also an ion and missing one electron. You are a sodium ion (Na+). You have one less electron than your atomic number.

=ION CHARACTERISTICS= So now you've become a sodium ion (Na+). Now you have ten electrons. That's the same number as neon (Ne). But you aren't neon (Ne). Since you're missing an electron you aren't really a complete sodium (Na) atom either. You are now something completely new. An ion. Your whole goal as an atom was to become a "happy atom" with completely filled **electron orbitals**. Now you have those filled shells. You are stable. What do you do that's so special now? Now that you have given up the electron, you are quite electrically attractive. Other electrically charged atoms (ions) are now looking at you and seeing a good partner to bond with. That's where chlorine comes in.

=ELECTROVALENCE= Don't get worried about the big word. **Electrovalence** is just another word for something that has given up its electron and become an ion. If you look at the periodic table, you might notice that elements on the left side usually become positively charged ions and elements on the right side get a negative charge. That trend means the left side has a positive valence and the right side has a negative valence. Valence is a measure of how much an atom wants to bond with other atoms.

There are two main types of bonding, **covalent** and **electrovalent**. Scientists also call ionic bonds electrovalent bonds. **Ionic bonds** are just groups of charged ions held together by electric forces. Scientists call these groups ionic agglomerates. When in the presence of other ions, the electrovalent bonds are weaker because of outside electrical forces and attractions.

Look at sodium chloride (table salt) as an example. Salt is a very strong bond when it is sitting on your table. It would be nearly impossible to break those ionic bonds. However, if you put that salt into some water the bonds break very quickly. It happens easily because of the electrical attraction of the water. Now you have sodium (Na+) and chloride (Cl-) ions. Remember that ionic bonds are normally strong but very weak in water.

=NEUTRON MADNESS= We have already learned that ions are atoms that are either missing or have extra electrons. Let's say an atom is missing a neutron or has an extra **neutron**. That type of atom is called an **isotope**. An atom is still the same element if it is missing an electron. The same goes for isotopes. They are still the same element. They are just a little different from every other atom of the same element.

There are a lot of carbon atoms in the universe. The normal ones are carbon-12. Those atoms have 6 neutrons. There are a few straggler atoms that don't have 6. Those odd ones may have 7 or even 8 neutrons. As you learn more chemistry, you will probably hear about carbon-14. Carbon-14 actually has 8 neutrons (2 extra). C-14 is considered an isotope of the element carbon.

=MESSING WITH THE MASS= If you have looked at a periodic table you may have noticed that the atomic mass of an element is rarely an even number. That happens because of the isotopes. If you are an atom with an extra electron, it is no big deal. Electrons don't have much of a mass when compared to a neutron or proton.

Atomic masses are calculated by figuring out how many atoms of each type are out there in the universe. For carbon, there are a lot of C-12, a couple C-13, and a few C-14 atoms. When you average out all of the masses, you get a number that is a little bit higher than 12 (the weight of a C-12 atom). The mass for element is actually 12.011. Since you never really know which C atom you are using in calculations, you should use the mass of an average C atom.

=RETURNING TO NORMAL= If we look at the C-14 atom one more time we can see that C-14 does not last forever. There is a point where it loses those extra neutrons and becomes C-12. That loss of the neutrons is called **radioactive decay**. That decay happens regularly like a clock. For carbon, the decay happens in a couple of thousand years. Some elements take longer and others have a decay that happens over a period of minutes.

=COMPOUND BASICS= Compounds are groups of two or more elements that are bonded together. There are two main types of bonds that hold those atoms together, covalent and electrovalent/ionic bonds. **Covalent** compounds happen when the atoms share the electrons, and **ionic** compounds happen when electrons are donated from one atom to another.

We talked about compounds and molecules in the matter tutorials. When we discuss **phase changes** to matter, physical forces create the changes. When we talk about compounds, bonds are built and broken down by chemical forces. **Physical forces** (unless you're inside of the Sun or something extreme) cannot break down compounds. **Chemical forces** are forces caused by other compounds or molecules that act on substances.

There are millions of different compounds around you. Chances are everything you can see is one type of compound or another. When elements join and become compounds, they lose their individual traits. Sodium alone is very reactive. But when sodium and chlorine combine, they form a non-reactive substance called sodium chloride (Salt, NaCl). The compound has none of the traits or the original elements. The new compound is not as reactive as the original elements. It has a new life of its own.

=DIFFERENT BONDS ABOUND= Most compounds are made up of combinations of bonds. If you look at sodium chloride (NaCl), it is held together by one ionic bond. What about magnesium chloride (MgCl2)? One magnesium (Mg) and two chlorine (Cl) atoms. There are two ionic bonds. There's a compound called methane (CH4). It is made up of one carbon (C) and four hydrogens (H). There are four bonds and they are all covalent. Those examples are very simple compounds, but most compounds are combinations of ionic and covalent bonds.

Let's look at sodium hydroxide (Na-OH).

You can see that on the left is the sodium (Na) part and the right has the oxygen/hydrogen (-OH) part. The bond that binds the hydrogen (H) to the oxygen (O) is covalent. The sodium (Na) is bonded to the hydroxide part of the compound with an ionic bond. This is a very good example of how there can be different types of bonds within one compound.

=Elements as Building Blocks= As you probably saw, the **periodic table** is organized like a big grid. The **elements** are placed in specific places because of the way they look and act. If you have ever looked at a grid, you know that there are rows (left to right) and columns (up and down). The periodic table has rows and columns, too, and they each mean something different.

=You've got Your Periods...= Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows is considered to be a different **period** (Get it? Like PERIODic table.). In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of [|atomic orbitals]. Every element in the top row (the first period) has one orbital for its [|electrons]. All of the elements in the second row (the second period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the maximum number of electron orbitals or electron shells for any element is seven.

=...and Your Groups= Now you know about periods. The periodic table has a special name for its columns, too. When a column goes from top to bottom, it's called a **group**. The elements in a group have the same number of electrons in their outer orbital. Every element in the first column (group one) has one electron in its outer shell. Every element on the second column (group two) has two electrons in the outer shell. As you keep counting the columns, you'll know how many electrons are in the outer shell. There are some exceptions to the order when you look at the [|transition elements], but you get the general idea.

=Two at the Top= Hydrogen (H) and helium (He) are special elements. [|Hydrogen] can have the talents and electrons of two groups, one and seven. To scientists, hydrogen is sometimes missing an electron, and sometimes it has an extra. [|Helium] is different from all of the other elements. It can only have two electrons in its outer shell. Even though it only has two, it is still grouped with elements that have eight ([|inert gases]).

The elements in the center section are called transition elements. They have special electron rules.

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