I know matter can be classified into groups with similar properties.I know matter is conserved.I know methods for separating mixtures based on the properties of the components.Matter, matter everywhere.There's matter in your hair.Matter in the air.There's even matter in a pear!There's liquid matter, solid matter, and matter that's a gas.Even you are matter, because you have volume and mass!

Poem by: Steve Tomecek

Within the realm of what we know exists - there is a lot of “stuff,” from stars and planets to oceans, wind and microscopic beings. The way that we know this stuff exists is that we can experience it; it all has a mass and takes up some space or has “volume.” All things that have these physical characteristics of mass and volume are considered “matter.” So, what is matter made of? In spite of the many forms that matter may take, at its most basic level, all matter is composed of tiny particles called atoms.

History of Composition of MatterThe earliest humans were curious about the various materials that they found around them—materials used to hunt for food, make clothing and medicines, and the myriad other manifestations of matter that made up their physical environment.

The ancient Greek philosophers and scientists Empedocles and Democritus, who lived around 400 B.C., proposed one of the first documented theories that attempted to describe the things around us. Empedocles argued that all matter was composed of four elements: fire, air, water, and earth. He further theorized that the ratio of these four elements determined the properties of the matter.

Figure 1: Early humans believed every material was made of differing proportions of Fire, Air, Water and Earth

Early scientists also imagined that there might be a point at which you could no longer cut a material in half any further. After much debate and experimentation, they agreed that indeed, an object could not be cut in half again and again indefinitely. They reasoned that sooner or later the object would become so small that it could not be divided again. This raised the question of the existence of a smallest indivisible unit. They called this indivisible particle an “Atom.” (Atom is the Greek word meaning “not to be cut” or “indivisible”).

Atoms and the Differentiation of MatterIf all matter is, at its most basic level, made of the same things—atoms—then what accounts for the seemingly infinite forms of matter we know to exist? Much of the differentiation comes from the fact that we know of approximately 118 different types of atoms, called elements, which interact and combine to create millions of different compounds, all of which are used to

make different forms of matter. These different atoms are made of differing amounts of protons, neutrons and electrons whose proportions determine their physical and chemical characteristics.

Atoms and the Properties of MatterPhysical properties of matter vary based on the density of the atoms which make them up, as well as other characteristics (see Figure 3 below)). Density is a relation of the mass of a substance (how many atoms are present) to the volume which the mass occupies.

Figure 2: Some examples of more specific distinguishing properties of matter

A BFigure 3: Box A represents a greater density of atoms than Box B

The spacing of atoms and the ease with which they can move past each other affects the “state” or form in which the matter appears. For example, in some substances the atoms are spaced far apart so they can easily move past each other and collide infrequently, in which case the substance would then be a gas. If the atoms are compressed so closely that they can only vibrate slightly, the substance will appear as a solid. Matter is able to be transformed into different states by the addition or removal of energy. All of the matter that we experience in the universe is in one of five states: they are solid, liquid, gas, plasma or a newly discovered state, a Bose-Einstein condensate.

Atoms and Classification of MatterScientists have come up with methods of describing and differentiating between the wide varieties of matter in our universe. Because different substances are made of different combinations and types of atoms, they have distinct properties. Scientists have created systems to describe and measure properties of matter. Matter is usually classified generally into different classes of substances and mixtures, and then further, more specifically, classified from there (see Figure 5).

Some properties of matter:

color taste melting

point boiling point density opacity

luster hardness mass volume length shape reactivity

MatterAnything with mass and volume.

Substance Matter with constant composition

MixtureMatter with variable composition

ElementSubstance made up of

only one type of atom

CompoundTwo or more

elements that are chemically combined

Heterogeneous MixtureMixtures that are made up of more than one phase

Homogeneous MixturesAlso called solutions.  Mixtures that are made up of only one phase

Examples - gold, silver, carbon, oxygen and hydrogen

Examples - water, carbon dioxide, sodium bicarbonate, carbon monoxide

Examples - sand, soil, chicken soup, pizza, chocolate chip cookies.

Examples - salt water, pure air, metal alloys, seltzer water.

Figure 4: General Levels of Classification of Matter

Figure 5: Law of the Conservation of Mass, illustrated

MixturesA mixture is a combination of two or more pure substances that maintains its individual chemical properties. They are combinations of elements or compounds. Mixtures are not combined chemically, but instead are held together by physical forces called intermolecular forces, which help determine the properties of the substances.

Intermolecular forces occur when atoms of molecules are attracted to other molecules in a chemical bond. They cause atoms to form solid and liquid phases. In the gas phase, the molecules are too far apart for the intermolecular forces to have any effect. Types of MixturesMixtures do not appear at first glance to be made of a single kind of matter. A mixture that has visibly different parts or is not distributed the same throughout are said to be heterogeneous. Heterogeneous mixtures may also exist in the three states of matter; solid, liquid, or gas. Other mixtures that do not contain visibly different parts or the same throughout are said to be homogeneous. Homogenous mixtures are also called solutions.

Figure 1. Types of Mixtures Heterogeneous MixturesThere are two types of heterogeneous mixtures; suspensions and colloids. A suspension mixture is a mixture containing particles that tend to settle down to the bottom, if left undisturbed. For example, if one were to place sand, clay and water into a bottle, shake it, and then leave it on a table undisturbed, hours later the layer of sand would be settled or suspended at the very bottom with a layer of clay on top, followed by a layer of water on top of the layer of clay. As a result of sand’s density, because it is denser than that of the layer of clay and the layer of water, it settles at the bottom.Homogeneous MixturesHomogeneous mixtures are mixtures that are consistent in appearance and composition throughout. Homogeneous mixtures are too thoroughly combined to be distinguished from one another by visual observation. Many homogeneous mixtures are commonly referred to as solutions or colloids.

ColloidsColloids are homogeneous mixtures in which particle sizes are larger than those in a solution but smaller than those in a suspension. Colloid mixtures may have components that exist in one or two states of matter. In a colloid mixture, particles will remain in its current state of matter, unlike a suspension mixture or heterogeneous mixture where if left undisturbed particles will settle to the bottom. For example, jelly, milk, blood, fog, glue, and paint will not settle but remain in its current state of matter.

Figure 2. Colloid particle sizes are greater than those normally discussed in many chemistry application (i.e., colloids are greater in size than atoms, molecules, and even polymers).

SolutionsA solution is a homogeneous mixture consisting of two or more pure substances in a single physical state of matter. Particles in a solution are very small and unable to be seen by the naked eye, such as atoms, molecules, or ions. They are evenly distributed throughout the solution in a uniform manner. For example, a spoonful from any part of the pitcher of lemonade will taste equally sweet. In addition, regardless of how long a solution is left undisturbed under consistent conditions, the particles in the solution will not separate.

Figure 3. Solutions Properties of SolutionsIn a solution, one substance is usually considered to the solute. A solute is a substance that is being dissolved or broken down in another substance in a solution. The substance that does the dissolving of the solute in a solution is called the solvent. For example, a solution of seawater consists of salt as the solute and water as the solvent. The salt is being dissolved in the water to make a solution of seawater.

Soluble and Insoluble SubstancesSubstances that are able to be dissolved in another substance are said to be soluble in that substance. For example, sugar and salt are both soluble in water because both solutes are able to be dissolved in water. Substances that are unable to be dissolved in another substance are said to be insoluble; unable to be dissolved in a solvent. Mercury and oil are examples of insoluble substances when placed in water. As a general rule of thumb, there will be usually more solvent than solute in a solution.

Figure 5. Concept map of mixtures

Factors Affecting Dissolving RateFactors that determine the rate at which a substance dissolves depend on the solubility of the solvent and solute. The rate at which a substance dissolves may be influenced by factors such as temperature, stirring, pressure, and surface area of dissolving substance.

Temperature and SolubilitySolubility may be influenced by temperature. The higher the temperature of the substance, the farther apart and faster the molecules will move due to the increase average kinetic energy of the molecules. The higher the temperature rises, the greater the average kinetic energy and as a result, molecules of the solvent, will on average begin to collide with the surface of the solute more frequently and with much more force. Thus, the solubility of most solid substances increases as the temperature of the solvent increases. For example, in warmer water, more solid will dissolve.

Conversely, the solubility of most gases becomes greater in colder temperatures rather than in warmer temperatures. The higher the temperature of a gas, the less soluble it becomes and the faster the gas molecules move, escaping from the liquid state. Thus, the solubility of the gaseous substances decreases as the temperature of the solvent increases.

Stirring and SolubilitySolubility may also be influenced by stirring. Stirring affects the rate at which a solute dissolves. By agitating a solution, it will increase the rate of contact among colliding molecules of both solvent and solute with each other. By stirring a solution, one is also increasing the amount of kinetic energy, thus allowing for the molecule’s bonds to become weakened and broken.

Pressure and SolubilityPressure changes have minute effects on solid and liquid solutes’ solubility. However, an increase in pressure of a gaseous solute will have a greater effect on its solubility. Increasing the pressure of a gaseous solute, increases the number of collisions experienced between the particles of the gas and of the liquid, therefore, increasing the solution’s solubility. For example, removing a cap on a soda bottle releases pressure and the gaseous solute bubbles out of solution. Likewise, decreasing the pressure of a gaseous solute, decreases the interaction between particles of the solute and solvent and as well as its solubility.

Surface Area and SolubilityLastly, solubility may be influenced by the amount of surface area of the dissolving substance. The smaller particle is, the faster the solute will dissolve in the solvent. Dissolving solutes in a solution occurs at the surface of the solvent. The larger the surface area of the particle, the slower the process for breaking down the solute will be to the colliding molecules. Conversely, decreasing the size of the particles will increase the solute’s surface area, where one will be able to increase the rate of dissolution. For example, a spoonful of granulated sugar will dissolve faster than a sugar cube because the smaller particles in the granulated sugar render a much greater surface area to the colliding water molecules.

ActionEffect

solid solute gaseous soluteshake or stir increased rate decreased rate

increase temperature increased rate decreased ratedecrease temperature decreased rate increased rate

increase pressure N/A increased rateincrease solute's surface area increased rate N/A

Table 1. Factors Affecting Dissolving Rate

Types of SolutionsThere are several possible combinations of solute to solvent physical states. The most common are solid, gaseous, liquid, and aqueous solutions.

Solution TypeComposition

ExamplesSolvent Solute

Gaseous gas gas air

Liquidliquid gas club sodaliquid liquid vinegarliquid solid Kool-Aid

Solidsolid liquid dental amalgamSolid solid steel, brass

Table 2. Composition of Solutions

The most common solid solutions contain two or more metals and are called alloys. Alloys are constructed by melting the component metals, mixing them together, and then allowing them to cool. Properties of an alloy are different from the properties of the component metals. Alloys may possess characteristics such as greater strength, greater resistance to corrosion, and higher melting points.

Gaseous solutions are mixtures with molecules spread relatively far apart and in constant random motion. When two or more gases are mixed together, the molecules quickly become intermingled in a uniformed composition. Because the molecules in a gas are so far apart, gaseous solutions may easily add more gas particles to change the composition of the solution. Properties of gaseous solutions depend on the properties of its components.

Within liquid solutions, the solvent and the solution are in a liquid state of matter. The solute may be a gas, a liquid, or a solid. Unlike gases, which can easily add more gas particles to change the composition of the solution, have limits to the amount of liquid solutes that may dissolve in liquid solvents. Liquid solutions that have pairs that may mix in any amount are called miscible, such as water and ethanol. Liquids that are unable to mix in any amount are called immiscible. Oil and water are an example of a liquid solution that is immiscible. Solutions that are in water as the solvent are called aqueous solutions. Substances that are able to dissolve in water are categorized to whether they give way to ions or molecules in the solutions. Ionic compounds that dissolve separate into positive and negative ions and become enclosed by water molecules. These positive and negative solute ions are free to move around, allowing for

an electric current to pass through the solution. A substance that dissolves in water separating into positive and negative ions and conducts an electric current is called an electrolyte.

Figure 10. Using a magnet to separate iron filings from sand

1. Incorrect assumption: when mixtures change in physical appearance, the substances also change in chemical make-up.Mixtures can be combinations of elements or compounds. Most substances found in nature are mixtures. A pure element or a pure compound is rarely found. Mixtures can be in any of the four phases of matter or they can be in combinations of different phases. For example, air is a mixture of gases, milk is a mixture of solids and liquids, alloys are mixtures of solids. 2. Incorrect assumption: when things dissolve, they disappear. When a solute dissolves into a solvent, the solute particles fill the spaces between the solvent particles. The solute is still present however now it is in solution. Solutions can be solids dissolved in liquids. They could also be gases dissolved in liquids (such as carbonated water). There can also be gases in other gases and liquids in liquids. If you mix things up and they stay at an even distribution, it is a solution. You probably won't find people making solid-solid solutions in front of you. They start off as solid/gas/liquid-liquid solutions and then harden at room temperature. Alloys with all types of metals are good examples of a solid solution at room temperature. A simple solution is basically two substances that are going to be combined. One of them is called the solute. A solute is the substance to be dissolved (sugar). The other is a solvent. The solvent is the one doing the dissolving (water). 3. Incorrect assumption: solutions can be separated by filtration.Solutions are homogeneous and cannot be filtered to separate into two different substances. Mixtures can be filtered. For example, sugar and water form a solution when mixed together. The sugar becomes evenly distributed throughout the solution, so that one portion is not sweeter than another. The dissolved portion of the solution (sugar) is called the solute and the dissolving portion (water) is the solvent. If more sugar is added to the solution, the entire solution becomes sweeter and we say that it is more concentrated. In solution, sugar and water have not lost their properties, only combined them. Pouring a solution, like sugar and water, through filter paper will not separate the mixture; the sugar particles are too small. The best method is distillation; the water evaporates and the sugar is left behind.4. Incorrect assumption: atoms can be seen with an optical microscope.Atoms cannot be seen with an optical microscope. The extent of an atom’s small size is often not well understood. For example, there are about one million atoms across the width of human hair. With atoms being so small, it is not possible to see them optically.Atoms however, have been “seen,” or more precisely, imaged using electron and atomic force microscopes. Electron microscopes use accelerated electrons instead of light to get increased resolution over optical microscopes. However, even electron microscopes can only see the largest atoms (e.g., uranium). Atomic force microscopes can image even smaller atoms by using nanotechnology. In essences, very small probes move over the atomic structure, providing a “pressure map,” in which the shape, size, and other properties can be inferred. 5. Incorrect assumption: particles possess the same properties as the materials they compose. For example, atoms of copper are "orange and shiny," gas molecules are transparent, and solid molecules are hard. All atoms contain the same three parts, protons, neutrons and electrons, only in different proportions. The properties of matter are determined by the interactions of the atoms with each other and the environment (e.g., how far apart the atoms are, what they are bonded to, and how they interact with light).6. Incorrect assumption: atoms have characteristics of living things.The movement in atomic particles is contributed to electrostatic forces, not life.

1. Mystery: Structure of the Atom - A Case for Indirect Evidence Because we can’t “see” atoms, students may wonder how we know matter is made of these particles. This website provides four activities which use everyday items to illustrate how scientists can use indirect evidence to figure out the properties of substances to small to see by how they interact with other substances. The access the lab information visit http://www.iit.edu/~smile/ch9211.html2. What is Matter? Worksheets On this website Jefferson Labs provides worksheets along with their answer keys which can be used to provide reinforcement when studying the parts of atoms, the building blocks of matter. To access these worksheets, go to http://education.jlab.org/beamsactivity/6thgrade/whatismatter/stu01.l.html3. Describing Matter Vocabulary ActivitiesHosted by Quia, the website provides a medium for educators to create and share educational games, quizzes, and activities, this application provides three different mediums for practicing vocabulary related to matter. Students can test their knowledge of matter related vocabulary and continue to familiarize themselves with terminology through flashcards, a matching game, concentration game and a word search. This application can be found at http://www.quia.com/jg/504943.html.4. Particle Nature of Matter ActivityNeed some ideas for activities that address the particle nature of matter? The following website provides student handouts and teacher keys for many activities which can be used to access and reinforce student understanding of the particulate nature of matter. These activities address molecular motion, density, states of matter, phase changes, and they address misconceptions about the spacing of particles in different states of matter.To download this activity, go to http://www.doe.state.la.us/lde/uploads/4249.pdf5. Harcourt School States of Matter Simulation On this website, Harcourt provides a wonderful interactive simulation on how temperature affects the spacing and movement of particles when a substance moves between a solid, liquid and gaseous state. The students can witness at the atomic level what is happening to the atoms.To view the simulation visit http://www.harcourtschool.com/activity/states_of_matter/6. Ask Grandpa – Interactive trip following the discovery of the composition of matterThe Ask Grandpa website provides a historical tour of experimental research on the topic of matter and atom discovery. The information is presented by cartoon images of the scientists and the information regarding their discoveries is simple and straight to the point.For this interactive tour go to http://www.usoe.k12.ut.us/CURR/SCIENCE/sciber00/7th/matter/sciber/timeline.htm7. Vision Learning – Dalton’s Playhouse This is another website which helps students understand the history and happenstance behind the discovery of the atom. In this virtual tour of the scientist’s laboratories, students are able to take part in the experiments that led to the discovery of the atom. After each experiment, students are asked a series of questions to check their understanding. After completing the virtual labs successfully, the students can even print a certificate. Visit Dalton’s Playhouse at http://web.visionlearning.com/dalton_playhouse/ad_loader.html8. How Big is an Atom? This website provides a very simple, but powerful activity which gives students a better idea as to how small atoms really are. The students are asked the following question. If they are given an atom of gold for every second since the big bang, would they be rich? You’ll have to look at the website to find out…To find the answer, visit http://www.pitt.edu/~jdnorton/Goodies/size_atoms/index.html