Chapter 1 Objectives Distinguish between elements and compounds. Section 3 How Is Matter Classified? Objectives Distinguish between elements and compounds. Distinguish between pure substances and mixtures. Classify mixtures as homogenous or heterogeneous. Explain the difference between mixtures and compounds.

Chapter 1 Classifying Matter Section 3 How Is Matter Classified? Classifying Matter An atom is the smallest unit of an element that maintains the properties of that element. Matter exists in many different forms but there are only 110 types of atoms. Atoms are joined together to make up all the different kinds of matter.

Oxygen (O) and Silicon (Si) Common elements: More than 90% of the atoms in the universe are…? Hydrogen (H) Which two elements make up 70+% of the mass of the Earth’s crust? Oxygen (O) and Silicon (Si) Living things are composed primarily of these four elements…? Carbon (C), Hydrogen (H), Oxygen (O) and Nitrogen (N)

Chapter 1 Pure Substances Section 3 How Is Matter Classified? Pure Substances A pure substance is a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. Elements are pure substances that only contain one kind of matter. They cannot be separated or broken down into simpler substances by chemical means. Each element has its own unique set of physical and chemical properties.

Chapter 1 Section 3 How Is Matter Classified? Pure Substances

Elements are Pure Substances Chapter 1 Section 3 How Is Matter Classified? Elements are Pure Substances Each elements is represented by a distinct chemical symbol.

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Elements as Single Elements or Molecules A molecule is the smallest unit of a substance that keeps all of the physical and chemical properties of that substance. A molecule usually consists of two or more atoms combined in a definite ratio. Diatomic elements exist as two atoms of the same element joined together.

Diatomic Elements (Molecules): Br I N Cl H O F Nitrogen (N) Bromine (Br) Iodine (I) Oxygen (O) Chlorine (Cl) Fluorine (F) Hydrogen (H)

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Some Elements Have More Than One Form Some elements, such as oxygen, phosphorus, sulfur, and carbon have many different forms called allotropes. An allotrope is the same element with a different arrangement of atoms. In the solid state of matter, carbon has 3 allotropes based on the arrangement of the atoms: diamond graphite fullerene The properties of allotropes vary widely.

Allotropes (of Carbon) Diamond, graphite and the bucky ball are all allotropes of Carbon.

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Some Elements Have More Than One Form, continued Oxygen exists as allotropes. Oxygen gas (O2) is colorless and odorless. Ozone (O3) is toxic and pale blue. Both are pure oxygen

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Compounds are Pure Substances Pure substances that are not elements are compounds. Compounds are composed of more than one kind of atom. example: carbon dioxide (CO2) There may be easier ways of preparing them, but compounds can be made from their elements. Compounds can be broken down into their elements, though often with great difficulty.

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Compounds are Represented by Formulas Because every molecule of a compound is made up of the same kinds of atoms arranged the same way, a compound has characteristic properties and composition. Compounds can be represented by an abbreviation or formula. A formula has subscripts which represent the ratio of different atoms in the compound. example: H2O has 2 hydrogen atoms and one oxygen atom

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Compounds are Represented by Formulas, continued Molecular formulas give information only about what makes up a compound. example: the molecular formula for aspirin is C9H8O4 A structural formula shows how the atoms are connected This two-dimensional model does not show the molecule’s true shape.

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Compounds are Represented by Formulas, continued A ball-and-stick model shows the distances between atoms and the angles between them in three dimensions. A space-filling model attempts to represent the actual sizes of the atoms and not just their relative positions. A hand-held model can provide more information than models shown on the flat surface of the page.

Pure Substances, continued Chapter 1 Section 3 How Is Matter Classified? Pure Substances, continued Compounds are Represented by Formulas, continued These models convey different information about acetylsalicylic acid (aspirin).

Chapter 1 Section 3 How Is Matter Classified? Mixtures A mixture is a combination of two or more substances that are not chemically combined. Air is a mixture of mostly nitrogen and oxygen. All the different gases in air are physically mixed. The proportions of the gases can vary. Water is not a mixture. The H and O atoms are chemically bonded The ratio of H to O atoms is always 2 to 1.

Chapter 1 Mixtures, continued Section 3 How Is Matter Classified? Mixtures, continued Mixtures Can Vary in Composition and Properties The proportion of the materials in a mixture can change. The properties of the mixture may vary. An alloy is a solid mixture. example: An alloy of gold and other metal atoms is stronger than pure gold. 18-karat gold contains 18 grams of gold per 24 grams of alloy. 14-karat gold contains 14 grams of gold per 24 grams of alloy.

Chapter 1 Particle Models for Gold and Gold Alloy

Chapter 1 Mixtures, continued Homogenous Mixtures Section 3 How Is Matter Classified? Mixtures, continued Homogenous Mixtures A homogenous mixture describes something that has uniform structure or composition throughout. examples: gasoline, syrup, and air Because any two samples of a homogenous mixture will have the same proportions of ingredients, homogenous mixtures have the same properties throughout.

Chapter 1 Mixtures, continued Heterogeneous Mixtures Section 3 How Is Matter Classified? Mixtures, continued Heterogeneous Mixtures A heterogeneous mixture describes something that is composed of dissimilar components. example: A mixture of sand and water is a heterogenous mixture. Any two samples of a heterogeneous mixture will have the different proportions of ingredients. Heterogeneous mixtures have different properties throughout.

Chapter 1 Examples of Mixtures Section 3 How Is Matter Classified? Examples of Mixtures Mixtures are either homogenous or heterogeneous.

Chapter 1 Section 3 How Is Matter Classified? Types of Mixtures

Chapter 1 Mixtures, continued Distinguishing Mixtures from Compounds Section 3 How Is Matter Classified? Mixtures, continued Distinguishing Mixtures from Compounds The properties of a mixture reflect the properties of the substances it contains. The properties of a compound often are very different from the properties of the elements that make it up. A mixture’s components can be present in varying proportions. A compound has a definite composition in terms of the masses of its elements.

PURE SUBSTANCE OR MIXTURE? Dirt Paint Dust Diamond Sea- water Water Glucose MIXTURE MIXTURE MIXTURE PURE SUBSTANCE MIXTURE PURE SUBSTANCE PURE SUBSTANCE

Chapter 1 Section 3 How Is Matter Classified? Classifying Matter