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Matter

Matter. Chapters 2.1, 3.1, 3.2, 3.3. Standards for this Unit. California Science Standard 8.3: Structure of Matter c. Students will know atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers.

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Matter

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  1. Matter Chapters 2.1, 3.1, 3.2, 3.3

  2. Standards for this Unit California Science Standard 8.3: Structure of Matter c. Students will know atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers. d. Students will know the states of matter (solid, liquid, gas) depend on molecular action. e. Students will know that in solids the atoms are closely locked in [position and can only vibrate; in liquids the atoms and molecules are more loosely connected and can collide with and move past one another; and in gases the atoms and molecules are free to move independently, colliding frequently.

  3. Section 2.1: Describing Matterpage 58 • What kinds of properties are used to describe matter? • What are elements, and how do they relate to compounds? • What are the properties of a mixture?

  4. What is Matter? • Matter is anything that • has mass, and • takes up space

  5. Characteristic Properties • Every form of matter has two kinds of characteristic properties: physical properties and chemical properties. • Characteristic properties: Properties that hold true for a particular kind of substance no matter what the sample is. • EXAMPLES: All diamonds have the same hardness; All water has a density of 1 gram/mL at STP • Since characteristic properties for a given substance never change, they can be used to identify the unknown matter.

  6. Physical Properties • A physical property is an observable characteristic of a pure substance. • Freezing point Flexibility / brittle • Boiling point Magnetic • Density Luster • Hardness Conductor of electricity • Texture State: liquid, solid, gas • Color

  7. Some Characteristic Properties • Boiling Points: The temperature at which a liquid boils • All liquids have a specific temperature at which they begin to boil • Examples: Water: 100o C Ethanol: 79o C Propane: - 42o C Table Salt: 1,465o C

  8. Some Characteristic Properties • Density: The amount of mass an object has in a specific volume • Density = mass (in grams) volume (in mL or cm3) • All pure substances have a characteristic density • Examples: Water: 1.0 g/mL Iron: 7.80 g/cm3 Gold: 19.30 g/cm3

  9. Chemical Properties A chemical property is a characteristic of a pure substance that describes its ability to change into another substance. • Flammability • Rust / tarnish • Chemically react with other substances

  10. The Make-up of Matter • All matter is made up of atoms. • Matter of one specific kind of atom is an element. • Matter of 2 or more elements chemically combined is a compound. • Elements and compounds occurring by themselves make up pure substances. • Matter of 2 or more substances not chemcially combined is called a mixture.

  11. Elements An element is a pure substance that cannot be broken down into any other pure substance by chemical or physical means. They are the simplest substances.

  12. Modeling an Atom Pencil “lead” is made of mostly graphite, a form of carbon. Two ways to model atoms used in this presentation are shown here for carbon.

  13. Modeling Molecules • Models of molecules often consist of colored spheres that stand for different kinds of atoms.

  14. Compounds • A compound is a pure substance made of two or more elements chemically combined in a set ratio. • Examples: • Salt: NaCl … ratio 1:1 • Sugar: C12H22O11 … ratio 12:22:11 • Carbon dioxide CO2 … ratio 1:2 • Water: H2O … ratio 2:1

  15. Ratios • A ratio compares two numbers. It tells you how much you have of one item compared to how much you have of another. For example, a cookie recipe calls for 2 cups of flour to every 1 cup of sugar. You can write the ratio of flour to sugar as 2 to 1, or 2:1. • The chemical formula for rust, a compound made from the elements iron (Fe) and oxygen (O), may be written as Fe2O3. In this compound, the ratio of iron atoms to oxygen atoms is 2:3. This compound is different from FeO, a compound in which the ratio of iron atoms to oxygen atoms is 1:1.

  16. Mixtures • A mixture is made of two or more substances (elements, compounds, or both) that are not chemically combined. • In a mixture: • All the substances retain their individual properties • The substances do not come in a set ratio • The substances are not chemically combined; they can be readily separated.

  17. Mixtures • There are two types of mixtures: • Heterogeneous mixtures --- a mixture where it is easy to tell that it is made up of different substances (like a salad) • Homogeneous mixtures --- a mixture where it looks like it is one substance; the parts are so evenly mixed (like salt water)

  18. The Make-up of Matter • All matter is made up of atoms. • Matter of one specific kind of atom is an element. • Matter of 2 or more elements chemically combined is a compound. • Elements and compounds occurring by themselves make up pure substances. • Matter of 2 or more substances not chemically combined is called a mixture.

  19. End of Section: Describing Matter

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