1. 2.1 Atoms, Ions, and Molecules KEY CONCEPT All living things are based on atoms and their interactions. 4

2. 2.1 Atoms, Ions, and Molecules Living things consist of atoms of different elements. An atom is the smallest basic unit of matter. Matter is anything that occupies space and has mass An element is one type of atom. H O Hydrogen atom (H) Oxygen atom (O) 4

3. 2.1 Atoms, Ions, and Molecules –The nucleus is made up of protons and neutrons. –Electrons float around in “energy levels” outside nucleus. Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) An atom has 2 parts: a nucleus & electrons. 4

4. 2.1 Atoms, Ions, and Molecules –water (H 2 O) O HH _ ++ A compound is a molecule containing atoms of different elements that are chemically combined (bonded) in a fixed ratio. 4

5. 2.1 Atoms, Ions, and Molecules –carbon dioxide (CO 2 ) –There are many other carbon-based compounds in living things!! A compound is made of atoms of different elements bonded together. –water (H 2 O) 4

6. 2.1 Atoms, Ions, and Molecules Warm - Up Sketch an atom. Label the nucleus, energy levels, electrons, protons, and neutrons.

7. 2.1 Atoms, Ions, and Molecules Analogy – baseball teams Ionic Bonds – 1 player (electron) switches to other team Covalent – The catcher catches for both teams The atoms in compounds can bond together in 2 different ways: –Ionic bonds form when atoms gain or lose electrons to each other (Ionic bonds are strong bonds) –Covalent bonds form when atoms share electrons (Covalent bonds are weak bonds) 4

8. 2.1 Atoms, Ions, and Molecules Ionic bonds form because of “ions” An ion is an atom that has gained or lost one or more electrons. –positive ions (made when an electron is lost) –negative ions (made when an electron is gained) Therefore…Ionic bonds can form form between the oppositely charged ions! Sodium atom (Na) Chlorine atom (CI ) Sodium ion (Na + ) Chloride ion (CI - ) Na loses an electron to CI ionic bond gained electron 4

9. 2.1 Atoms, Ions, and Molecules Atoms share pairs of electrons in covalent bonds. A covalent bond forms when atoms share a pair of electrons. covalent bonds Oxygen atom (O)Carbon atom (C)Oxygen atom (O) Carbon dioxide (CO 2 ) 4

10. 2.1 Atoms, Ions, and Molecules Molecules Molecules are formed when 2 or more atoms are held together by covalent bonds. Chemical formula: tells you the number and types of atoms in a molecule (example: H 2 O tells you that water has 2 hydrogen atoms and 1 oxygen atom) Structural formula: shows how atoms in a molecule are connected (by bonds) 4

11. 2.1 Atoms, Ions, and Molecules PRACTICE!!! 1.Determine if each is the chemical or structural formula of the molecule. KMnO 4 MgSO 4

12. 2.1 Atoms, Ions, and Molecules Chemical Reactions Chemical reaction: The breaking apart of old bonds and forming of new chemical bonds…resulting in a TOTALLY NEW SUBSTANCE. ( its like a math problem!) –Reactants: starting materials for a reaction –Products: ending materials from a reaction 1 + 1 = 2

13. 2.2 Properties of Water KEY CONCEPT Water’s unique properties allow life to exist on Earth. Objectives: Describe the structure of a water molecule List and describe water’s unique properties Distinguish between an acid & base Explain how Earth’s conditions are fit for life

14. 2.2 Properties of Water O HH _ ++ Life depends on hydrogen bonds in water. Water is a polar covalent molecule. –Polar molecules have slightly charged regions. –Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative oxygen atoms. – Nonpolar molecules do not have charged regions.

15. 2.2 Properties of Water Hydrogen bonds are responsible for 3 important properties of water: 1. High specific heat - water must absorb A LOT of heat before it gets “hot” (increases temp.) 2. Cohesion: tendency of like molecules to stick together 3. Adhesion: type of attraction that occurs between unlike molecules

16. 2.2 Properties of Water Cohesion & Adhesion --- DEMO Cohesion: tendency of like molecules to stick together Adhesion: attraction that occurs between unlike molecules

17. 2.2 Properties of Water Explain this picture using 2 of the 3 unique properties of water!

18. 2.2 Properties of Water Many compounds dissolve in water ------ DEMO. A solution is formed when one substance dissolves in another. –Solvents dissolves other substances. (H2O) –Solutes dissolve in a solvent. (NaCl) –Aqueous Solution – any solution where water is the solvent. solution

19. 2.2 Properties of Water “Like dissolves like” –Polar solvents dissolve polar solutes. –Nonpolar solvents dissolve nonpolar solutes. –Polar substances and nonpolar substances generally remain separate.

20. 2.2 Properties of Water Some compounds form acids or bases. An acid releases a hydrogen ion when it dissolves in water. –high H + concentration –pH less than 7 more acidic stomach acid pH between 1 and 3

21. 2.2 Properties of Water A base removes hydrogen ions from a solution. –low H + concentration –pH greater than 7 bile pH between 8 and 9 more basic

22. 2.2 Properties of Water A neutral solution has a pH of 7. See page 85 to view examples of Acids & Bases pure water pH 7