Classification of matter

1. Classification of matter

2. Find your lab tour paper to study for your safety test.

3. Qualitative/Quantitative Sucrose is composed of the elements carbon, hydrogen, and oxygen. This is a qualitativeexpression of composition. A qualitative observation is one that can be made without measurement. In 100 g of sucrose contains 42.1 g of carbon, 51.4 g of oxygen, and 6.5 g of hydrogen. This is a quantitativeexpression of composition. A quantitative observation is one that uses measurement. You make quantitative measurements every day when you answer such questions as What’s the temperature? How long was the pass?

5. Pure Substances/Mixtures A substance is matter with the same fixed composition and properties. A substance can be either an element or a compound. Any sample of pure matter is a substance. Most of the matter you encounter every day is a mixture. A mixtureis a combination of two or more substances in which the basic identity of each substance is not changed. Unlike pure substances, mixtures do not have specific compositions.

6. Physical Properties Physical properties are characteristics that a sample of matter exhibits without any change in its identity. Examples of the physical properties of matter include its solubility, melting point, boiling point, color, density, electrical conductivity, and physical state (solid, liquid, or gas).

8. Chemical Properties Chemical properties are those that can be observed only when there is a change in the composition of the substance. Chemical properties describe the ability of a substance to react with other substances or to decompose. Lack of reactivity is also a chemical property.

9. Atom • The smallest particle of an element that retains the properties of that element. • Idea of the atom was first suggested by Democritus

10. Electrons (e-) • first subatomic particle discovered • have a negative charge • equal to the number of protons and atomic number • discovered by J. J. Thomson • found in the electron cloud • amu 1/1897

11. Protons (p+) • have a positive charge • equal to the atomic number of the element • found in the nucleus of the atom • amu 1

12. Neutrons (n0) • have a neutral (no) charge • found in the nucleus of the atom • approximate amu 1

13. Nucleus • center of the atoms • composed of protons and neutrons • very dense • has a positive charge • discovered by Rutherford in his gold foil experiment.

14. Isotopes • atoms that have the same number of protons (thus the same element), but a different number of neutrons. • alike chemically, but have different masses • written with the name or symbol of the element followed by the mass number • Carbon-12 or carbon-14

15. Dalton’s Atomic Theory John Dalton (1766-1844) - an English schoolteacher and chemist The following statements are the main points of Dalton’s atomic theory. 1. All matter is made up of atoms. 2. Atoms are indestructible and cannot be divided into smaller particles. (Atoms are indivisible.) 3. All atoms of one element are exactly alike, but they are different from atoms of other elements.

17. Periodic Table

18. Electrons, Protons and Neutrons An atom’s atomic number is the number of protons in its nucleus. The number of electrons in an atom equals the number of protons. Atoms of the same element always have the same number of protons and electrons but vary in the number of neutrons. protons = atomic number electrons = protons neutrons = atomic mass - protons

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26. Electrons in Energy Levels Each energy level can hold a limited number of electrons. The lowest energy level is the smallest and the closest to the nucleus. This first energy level holds a maximum of two electrons. The second energy level is larger because it is farther away from the nucleus. It holds a maximum of eight electrons. The third energy level is larger still and holds a maximum of 18 electrons. The electrons in the outermost energy level are called valence electrons.

27. Lewis Dot Diagram A Lewis dot diagramillustrates valence electrons as dots (or other small symbols) around the chemical symbol of an element. Each dot represents one valence electron. The maximum number of dots on a the diagram is 8.

28. Lewis Dot Diagram

29. Lewis Dot Diagrams

30. Electrons in Energy Levels The period number tells the number of energy levels of an atom. Example sodium is in the _____ period, so it must have _____ energy levels.

31. p+ = ______ n0 = ______ e- = ______ Bohr Diagram Lewis Structure Na _____ Na _____________ _______