Introduction to Chemistry

Transcription

1 Introduction to Chemistry Chapter 11 Student Learning Objectives Distinguish between physical and chemical properties Classify, compare, name, and identify chemical quantities Analyze solubility Apply trends in the periodic table.

2 What is chemistry? Macroscopic Physics is a study of macroscopic properties. Large Scale Visible Microscopic Chemistry is the study of microscopic properties. Small Scale Invisible

3 What are some physical and chemical properties? Physical Properties (Macroscopic) Density Phase Appearance Size Chemical Properties (Microscopic) Atomic make-up Structure Reactivity

4 Practice 1) Name macroscopic properties of water. 2) Name microscopic properties of water. 3) How do carbon dioxide (CO 2 ) and water (H 2 O) compare and contrast?

5 The primary difference between a physical change and a chemical change is that a chemical change produces a new substance. Some Chemical Change Indicators Color change Gas Temperature Change Light Sound The Chemistry of Cookies

6 How are elements, molecules, compounds and mixtures defined? All of one type of atom is classified as an element. How the Elements Got their Names Question: What are the origins of the elements? Chemical bond attraction between atoms Molecular Formula relative numbers of atoms in bond Molecule atoms in a chemical bond

7 A compound contains two or more types of atoms. Type Number of Atoms Diatomic 2 Triatomic 3 Polyatomic 4+

8 Practice H 2 O CaF 2 NH 3 O 2 1) Which is not a compound? 2) How many atoms are contained in each? 3) Classify as diatomic, triatomic, or polyatomic.

9 A substance that is pure contains only one element (copper), or only one compound (salt). Homogeneous Mixture Same uniform appearance and composition throughout Solution (same phase) Soda Pop Heterogeneous Mixture Consists of visibly different substances or phases Suspension (particles settle) Mango Juice + Peach Juice

10 Practice: Classify each substance. 7-up Aluminum Alloy Homogenized milk Raw milk Oil and water Carbon monoxide Distilled water Air Tap water Homogeneous Mixture (Solution) Or Heterogeneous Mixture

11 How can mixtures be separated? Filtration Distilation Desalination separate liquids and solids separate gasses, liquids, solids combines distillation and reverse osmosis Water may cross a semi-permeable membrane. (Osmosis) Osmosis Demonstration With a Raw Egg Osmosis: from less to more concentrated Reverse osmosis: from more to less concentrated

12 Question Distillation and desalination are typically not used to obtain fresh water from salt water. Why?

13 Chemical Classification of Matter Section 11.1

14 What are the properties of a solution? Solvent (larger amount) Does the dissolving Water Solute (smaller amount) Dissolves Sugar Solubility is a measure of how much solute will dissolve in a solvent to produce a stable solution. Why don't Oil and Water Mix? Liquids may be miscible or immiscible. (mix or not mix) Oil and Water

15 Liquid Solutions Solvent the liquid or the substance in the larger quantity Solute the substance dissolved in the solvent Photo Source: Standard HMCO copyright line Section 11.1

16 Solubility is variable. Bond Strength Bond Types Temperature Pressure Molecular attractions Solubility (dissolving) has a limit, based on each individual substance and physical conditions. Concentrated solution Dilute solution Saturated solution Concentration = Grams Liter

17 Practice 1) If you cannot dissolve anymore sugar in your coffee, your coffee is? 2) What is the concentration when 5 grams of sugar is added to ½ a liter of water? 3) If you have 30 ml of 25% HCl solution, how many grams of HCL are in the solution?

18 Relative Abundance (by Mass) of Elements in Earth s Crust Note that 74% of the mass of the Earth s crust is composed of only two elements oxygen & silicon Section 11.3

19 Representations of Molecules Section 11.3

20 What are the basic trends in the periodic table? The genius of Mendeleevs periodic table The periodic table is periodic! Most of the elements in the periodic table are metals. Shiny Opaque Good conductors of electricity Question: Which metals are liquid under normal atmospheric conditions?

21 Atomic Periods (rows) are periodic. Atomic Groups (columns) have similar trends. 1 amu = x grams

22 One way to Classify the periodic table Representative Elements (green) Transitional Elements (blue) Inner Transition Elements (purple) Section 11.4

23 Metals/Nonmetals in the Periodic Table Section 11.4

24 We will basically only discuss the representative elements Groups 1A - 8A Section 11.4

25 Group Name Attributes IA Alkali Metals Highly Reactive IIA Alkali Earth Metals Middle IIIA VIA VIIA VIIIA Transition Metals Metalloids Halogen Gases Noble Gases High Melting Point Metals/ Non-metals Ore Forming Elements Salt Forming Elements Non-Reactive Emerald is a variety of beryl, a mineral that contains the alkaline earth metal beryllium.

26 Lanthanides (58-71): found in geologic zones Actinides (90-103): most are synthesized in labs The periodic table has trends. Chemical reactivity decreases L R. Radius decreases along a period L R. A Uranium Rock Ionization energy increases along a period L R.

27 Practice 1) Which of the following would be most reactive? a. O b. He c. Al d. Cl 2) Which of the following would have the smallest radius? a. Al b. Cl 3) In which group are the precious metals? 4) Use the periodic table to list the defining attributes of Bromine (Br).

28 What does the shell model indicate? No two electrons can have the exact same energy state. (Pauli Exclusion Principle) Electrons in an atom are arranged in particular orbitals Each electron has its own set of quantum numbers (n,l,m l, m s )

29 Atomic period indicates the number of main energy shells available in the ground state. Shell Number e - Allowed n = 1 2 n = 2 8 n = 3 8 n = 4 18 n = 5 18 n = 6 32 n = 7 32

30 Electron Shell Distribution for Periods 1,2,3 This is an important and very useful figure! Protons (Z) Electrons Section 11.4

31 Practice How many shells are available and how many electrons are in each shell? Assume each atom is in the ground state. 1. N 2. Kr 3. Mg 4. O

32 Valence Electrons Electrons attempt to have configurations that match those in group VIIIA. (Octet Rule) 8 Group Number = Number Unpaired e More unpaired electrons = more reactive Valence electrons are what make the physical and chemical properties of the atoms in a group similar.

33 What are some rules for naming compounds? Compounds Metal is named first and then the Non-metal Left then Right + ide NaCl = Sodium Chloride HF = Hydrogen Fluoride Prefixes 1. Mono 2. Di 3. Tri 4. Tetra 5. Penta 6. Hexa 7. Hept 8. Oct CO 2 = Carbon Dioxide

34 Practice What is the chemical name? Does it have a common name? 1. O 2 5. SF 6 2. H 2 O 6. CH 4 3. KBr 7. NH 3 4. O 3 8. PCl 5