1 2 3 Compounds, Mixtures, and Elements Topic 3 Oh My!!! http://dsc.discovery.com/videos/assignment-discovery-shortselements-compounds-and-mixtures.html 1. Three types of matter A. Mixture made of two or more kinds of matter that are physically combined or mixed together. Example: Salad 4 5 Observations of mixtures i. The properties of a mixture can vary because the composition of a mixture is not fixed. Other examples: Cinnamon and sugar, a bag of skittles? Hmmmm.. 6 7 ii. Can separate mixtures based on the physical properties of the matter Example: Salt water How do you separate the salt and the water? Gee, I can t even see the salt in the water. iii. Separate mixtures using: Evaporation separate solutions with heat Filtering remove visible solids in liquid Special properties like magnetic- works on solids 1
8 9 10 11 12 How would you separate this mixture? What will this separate? QUESTIONS iv. Homogenous vs heterogeneous mixture homogeneous: the same throughout heterogeneous: parts are different from Homogeneous or heterogeneous one another 13 v. Three types of mixtures Solutions, suspension, and colloids Solutions can be solids dissolved in liquids gases dissolved in liquids (such as carbonated water) gases in other gases and liquids in liquids. 14 15 16 17 18 Making a solution Making Solutions 1. The solute is placed in the solvent and the solute slowly breaks into pieces. 2. The molecules of the solvent begin to move out of the way and they make room for the molecules of the solute. Example: The water has to make room for the sugar molecules. 3. The solute and solvent interact with each other until the concentration of the two substances is equal throughout the system. To be or not to be a mixture? 2
Question: Are a bag of skittles a mixture? Design a procedure to answer the question. Your experiment must have the following: Question (1 pt) Hypothesis (1 pt) Procedure (2 pt) Must have one diagram Data Table (1 pt) Graph (1 pt) Conclusion (1 pt) 19 20 Colloids a mixture consisting of tiny particles dispersed in a solid, liquid, or gas Mixture Summary No definite chemical composition Each type of matter keeps its properties Can be separated by physical means Return to its original form Three types of mixtures Solutions, colloids, suspension Video quiz 21 B. Compounds: made up of atoms of two or more elements that are chemically combined. The elements are combined in a fixed ratio. 3
22 23 Example: Salt is made up of 1 atom of sodium and 1 atom of chlorine. NaCl Elements combine with other elements to become compounds. Example: hydrogen and oxygen are both elements that are gases but when they combine they make WATER!! 24 Properties of compounds are very different than the properties of the elements that make them up. Some elements may be very dangerous but when they combine to make a compound they are not. 25 26 Harvesting Salt 27 28 29 30 31 Poland Salt Mine 32 33 34 Quick video activity Salt Homework Compounds have physical and chemical properties that can be used to identify the compound. 4
Compounds have physical and chemical properties that can be used to identify the compound. 35 So how exactly are mixtures different than compounds? Compounds combine chemically (new bonds form)where mixtures combine physically (no bonds form). You can separate a mixture manually by their physical means but a compound you have to separate chemically with heat or with electricity (break bonds). 36 C. Ionic Bonding 1. Electron configuration Arrangement of electrons 2. Stable electron configuration The highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react 37 3. Electron dot diagram (Lewis diagram) model of an atom in which each dot represents the number of valence electrons (outer most shell) Valence electrons are equal to the elements group number (1-8) except He which only has 2 38 39 40 41 4. Ionic Bond Some elements achieve stable electron configurations through transfer of electrons between atoms. Who gives and who takes? Handout identifying ions and atoms 5
Handout identifying ions and atoms 42 6. Formation of ionic bonds Negative and positive charges are attracted A chemical bond is the force that holds atoms or ions together as a unit. Ionic bond is the force that holds cations and ions together 43 7. Ionization energy The amount of energy required to remove an electron 44 8. Ionic Compounds compounds that contain ionic bonds (look for a metal and a non-metal) 45 46 47 D. Covalent Bonding 1. When two atoms share a electrons a. One pair = a single bond b. Two pairs = a double bond c. Three pairs = a triple bond Let s practice- How many atoms in the valence orbit? Create a Lewis dot of the atoms So what are the differences between ionic and covalent bonds? -Atoms in Ionic Bonds gain or lose electrons. -Atoms in covalent bond share electrons. This means that the atoms do not become positively or negatively charged. The atoms remain neutral. 6
atoms do not become positively or negatively charged. The atoms remain neutral. 7