Classification of Matter

1. CHAPTER 15 Classification of Matter

2. Composition of Matter Matter is anything that has mass and takes up space. Ex: Your textbook, you, your pen/pencil, air, etc. Classification systems are used all the time to organize objects. Ex: The Periodic Table of Elements, organizing your locker, your clothes, etc. In order to make the study of matter easier to understand, scientists have developed ways to classify matter. The properties of materials can be used to classify them into general categories. Ex: Pure substances, elements, compounds, mixtures, etc.

3. Composition of Matter Materials are made of a pure substance or a mixture of substances. Substance: A type of matter with a fixed composition. A substance can either be an element or a compound. Ex: Helium, Aluminum, Water, Salt, etc. Elements are built from atoms. Atom: The smallest particle of an element that still retains the properties of the element. Element: Simplest type of pure substance. Elements cannot be changed into simpler substances by any physical or chemical means. About 90 elements are found on Earth, and more than 20 others have been made in the laboratory (radioactive). Ex: Iron (Fe), Carbon (C), Oxygen (O), Gold (Au), Uranium (U), etc.

4. Composition of Matter Each element is designated by a one or two letter symbol that is used worldwide. Symbols for the elements are always a single capital letter or a capital letter followed by a lowercase letter. Chemical symbols are just a shorthand way of representing the elements. Some of the symbols are from the Latin or German names. Ex: Tungsten (W = Wolfram), Sodium (Na = Nadium), Gold (Au = Aurum), Potassium (K = Kalium), Lead (Pb = Plumbum), etc. Each of the more than 110 elements that we know of is unique and has different properties from the rest.

5. Composition of Matter

6. Composition of Matter Compounds are pure substances made of atoms of two or more different elements that are chemically combined. Ex: Water (Hydrogen and Oxygen), Nylon (Carbon, Hydrogen, Nitrogen, and Oxygen), Table Salt (Sodium and Chlorine), etc. Every compound is different from the elements it contains. Ex: Water � made of two gases (hydrogen and oxygen). Ex: Salt � made of a metal (sodium) and a gas (chlorine). When elements combine to make a specific compound, the elements combine in the same proportions. Ex: Iron Oxide (rust) always has two atoms of iron for every three atoms of oxygen.

7. Composition of Matter Compounds can be broken down into simpler substances. Ex: Sugar = By heating sugar you can separate it into carbon and water vapor. Most compounds are made of molecules. Molecules: Made of two or more atoms chemically bonded together. A molecule is the smallest particle of a compound that has all the properties of that compound. All molecules of a compound are alike. A molecule may consist of two or more atoms of different elements or atoms of the same element. Ex: Water molecule = H2O, Oxygen molecule = O2, Phosphorus molecule = P4, Sulfur molecule = S8, Ozone molecule = O3, Sugar molecule = C6H12O6, Carbon Dioxide molecule = CO2, etc.

8. Composition of Matter A chemical formula shows how many atoms of each element are in a unit of a substance. In a chemical formula, the number of atoms of each element is written after the elements symbol as a subscript. If only one atom is present, no subscript number is used. Ex: Water = H2O, Table Salt = NaCl, Sugar = C6H12O6, Indigo = C16H10N2O2, Octane = C8H18, Hydrogen Peroxide = H2O2, etc.

9. Composition of Matter A mixture is a combination of two or more substances that are not chemically bonded. Ex: Grape juice � the composition is not fixed; it can have different amounts of water or sugar. Elements and compounds are pure substances, but mixtures are not. Mixtures are formed by mixing pure substances. A mixture can be separated into its components. Ex: The components of water, a pure substance, are chemically combined and cannot be separated in the same way that the components of grape juice can be separated.

10. Composition of Matter 3 Properties of Mixtures: Substances keep their own separate identities and most of their own properties. Ex: A mixture of salt and water. Substances can be present in any amount. Ex: 1 cup of water and 1 tablespoon of salt or 1 gallon of water and 1 cup of salt. Substances can be separated by simple physical means. Ex: Boiling the salt water will evaporate the water and the salt will be left behind. No chemical reactions are involved.

11. Composition of Matter There are two types of mixtures: Heterogeneous Mixture: A mixture that is not the same throughout. The substance�s are not mixed uniformly and are not evenly distributed. Ex: A flour and water mixture � they form a cloudy white mixture. Ex: Oil and water � the oil and water will not mix well together, and the water will settle out (immiscible liquids). 2. Homogeneous Mixture: Mixture that is the same throughout. The components are evenly distributed. Ex: A sugar and water mixture � you cannot see the sugar, and the mixture is clear. Ex: Gasoline is a liquid mixture � a homogeneous mixture of at least 100 liquids (miscible liquids).

12. Composition of Matter

13. Composition of Matter A solution is a homogeneous mixture of particles so small that they cannot be seen with a microscope and will never settle out to the bottom of their container. Ex: Lemonade, air, antifreeze, ocean water, etc. There are two properties of solutions: Particles are not large enough to see. Particles are evenly spaced out. Not all solutions are liquids. Ex: Alloys = Metal solutions. (Gold jewelry = Gold + Copper, Brass = Copper + Zinc, Sterling Silver = Copper + Silver, White Gold = Gold + Palladium, Stainless Steel = Chromium + Iron, etc.)

14. Composition of Matter A colloid is a type of mixture with particles that are larger than those in solutions but not heavy enough to settle out. Comes from the Greek word for glue. Ex: Milk (water, fats, proteins), Paint (particles suspended in a liquid), fog (water suspended in air), etc. One way to distinguish a colloid from a solution is by its appearance. Ex: Fog appears to be white because its particles are large enough to scatter light. Sometimes it is not so obvious that a liquid is a colloid. Ex: Shampoos and gelatins are colloids called gels that appear almost clear. You can tell if they are a colloid by passing a beam of light through it. A light beam is invisible as it passes through a solution, but it can be seen as it passes through a colloid. This scattering of light by colloidal particles is called the Tyndall Effect.

15. Composition of Matter Some mixtures are neither solutions nor colloids. A suspension is a heterogeneous mixture containing a liquid in which visible particles settle. Ex: Muddy pond water, river deltas, etc.

16. Composition of Matter

17. Properties of Matter Any characteristic of a material that you can observe without changing the identity of the substances that make up the material is a physical property. Ex: Color, shape, size, density, melting point, boiling point, volume, etc. Many physical properties can be observed or measured to help identify a substance. Ex: You can use your senses to observe some of the physical properties of a substance: shape, color, odor, and texture. Ex: Other physical properties, such as melting point, boiling point, strength, hardness, and the ability to conduct electricity, magnetism, or heat, can be measured.

18. Properties of Matter Because many physical properties remain constant for pure substances, you can use your observations or measurements of these properties to identify substances. Ex: At room temperature and atmospheric pressure, all samples of pure water are colorless and liquid; pure water is never a powdery green solid. A characteristic of any pure substance is that its boiling point and its melting point are constant if the pressure remains the same. Ex: At sea level, water boils at 100�C (212�F) and freezes at 0�C (32�F). At higher elevations, the boiling and melting points increases and vice-versa. Ex: The boiling point of water in a cars cooling system with a 15 psi radiator cap is about 250�F (121�C). It doesn�t matter if you have a lot of water or a little water; these physical properties of the water are the same regardless of the mass or volume involved.

19. Properties of Matter An easily observed physical property is state � the physical form in which a substance exists. Solids, liquids, and gases are three common states of matter. Solid: Matter with a definite shape and a definite volume Liquid: Matter with no definite shape but with a definite volume. Gas: Matter with no definite shape or volume.

20. Properties of Matter A change is size, shape, or state of matter is called a physical change. These changes might involve energy changes, but the kind of substance � the identity of the element or compound � does not change. Ex: Change in state (solid ? liquid ? gas). Because all substances have distinct properties like densities, specific heats, and boiling and melting points, these properties can be used to help identify them when a particular mixture contains substances which are not yet identified.

21. Properties of Matter The process for separating substances in a mixture by evaporating a liquid and recondensing its vapor is distillation. In distillation, the mixture is heated slowly until it begins to boil. Vapors of the liquid with the lowest boiling point form first and are condensed and collected. Then the temperature is increased until the second liquid boils, condenses, and is collected. This is continued until the mixture has been completely separated.

22. Properties of Matter Distillation is often used in industry. Ex: Petroleum When petroleum is separated, it is called fractional distillation. Fractional Distillation: Components of a mixture are separated on the basis of boiling point, by condensation of vapor in a fractionating column.

23. Properties of Matter During its fractional distillation, petroleum is heated to about 370�C. Nearly all the components of the petroleum are vaporized at this temperature. As the vapors rise in the fractionating column, or tower, they are gradually cooled. Those substances with high boiling points have higher condensation temperatures and condense for collection lower in the tower. Ex: Lubricating oils, which have high condensation temperatures than gasoline, are collected lower in the fractionating tower.

24. Properties of Matter A chemical property is a characteristic of a substance that indicates whether it can undergo a certain chemical change. Ex: Reactivity, flammability, etc. In general, chemical properties are not as easy to observe as physical properties. Ex: The brown color of medicine bottles tells you that the medicine inside may react to light. Chemical properties are related to the specific elements that make up substances. A chemical property describes how a substance changes into a new substance, either by combining with other elements or by breaking apart into new substances.

25. Properties of Matter A change of one substance to another is a chemical change. Ex: Foaming of an antacid tablet in a glass of water, the burning of gasoline, etc. In some chemical changes, a rapid release of energy � detected as heat, light, and sound � is a clue that changes are occurring. Three indications of a chemical change: Evolution of heat and light. Production of a gas. Formation of a precipitate. Precipitate: An insoluble solid formed by a reaction in solution. Ex: Lead Nitrate + Potassium Iodide ? Lead Iodide (precipitate) + Potassium Nitrate

26. Properties of Matter Because new substances are formed in a chemical change, you cannot reverse chemical changes by using physical changes. Ex: You cannot �un-bake� a cake by separating out each ingredient. Some chemical changes can be reversed under the right conditions by other chemical changes. Ex: The water formed in a space shuttle�s rockets can be split back into the starting materials � hydrogen and oxygen � by using an electric current (electrolysis) to initiate a reaction that separates the hydrogen and oxygen atoms in the water molecules. Electrolysis: The decomposition of a substance by an electric current.

27. Properties of Matter Compounds can be broken down through chemical changes. Ex: When Mercury (II) Oxide is heated, it breaks down into the elements mercury and oxygen. Ex: If an electric current is passed through melted table salt, the elements sodium and chlorine are produced. Ex: Cleaning silver tarnish � Tarnish is a chemical reaction between silver metal and sulfur compounds in the air which results in silver sulfide. It can be changed back into silver using a chemical reaction when the item is placed in a warm water bath with baking soda and aluminum foil. Ex: In a thunderstorm, the pungent smell of ozone (O3) indicates that a chemical reaction also took place. Lightning converts oxygen gas (O2) into ozone (O3). Ozone is unstable and soon breaks up forming oxygen again.

28. Properties of Matter According to the Law of Conservation of Mass, the mass of all substances that are present before a chemical change equals the mass of all the substances that remain after the change. In other words, matter is neither created nor destroyed during a chemical change. Ex: Burning a piece of paper/wood, combustion of gasoline, etc.

29. Properties of Matter Example: When a chemical reaction takes place, the total mass of reactants equals the total mass of products. If 18-grams of hydrogen react completely with 633-grams of chlorine, how many grams of Hydrogen Chloride are formed? H2 + Cl2 ? 2HCl 18-g H2 + 633-g Cl2 = 651-g HCl

30. Properties of Matter Weathering can involve both physical and chemical changes. Ex: Large rocks can split when water seeps into small cracks, freezes, and expands (Physical Change). Ex: Streams can cut through softer rock, forming canyons, and can cut and sculpt harder rock (Physical Change). Ex: Limestone (calcium carbonate) reacts with acid rain to form a new substance. Ex: The formation of stalactites.