Elements, Compounds, and Chemical Changes

1. Elements, Compounds, and Chemical Changes

2. Separation • How can you separate these solutions?? • Milk (proteins are suspended in solution) • Blood (cells and proteins are suspended in solution) • ___________________ • Yields two layers (solution on top, suspensions on bottom)

3. Density • Review: • Mass- How much matter is contained in an object • Volume- How much space an object takes up • Density- ??

4. Density Derivation • If density is the amount of matter per unit of volume, then what is the equation to calculate density? • Equation  __________________________ • How much space will a 54.8 g sample of Fe occupy if the density is 7.86 g/mL • Note: g/mL = g/cm3 = g*mL-1 = g*cm3-1

5. Graphical Analysis • Volume on the x-axis, Mass on the y-axis • As the volume increases for a given substance, so does the mass, at a constant rate. • The slope of this line is the DENSITY!! • We can determine the identity of an unknown substance using its density.

6. Atoms are the Fundamental Components of Elements • The Periodic Table contains a relatively small number of atoms that form an unlimited number of different materials. • This is based on how they combine or bond together

7. Atoms are the Fundamental Components of Elements • The Periodic Table contains a relatively small number of atoms that form an unlimited number of different materials. • This is based on how they combine or bond together • Element – Any material consisting of only one type of atom. • Atom – Submicroscopic particles in a sample. Each element is designated by a symbol (Atomic Symbol) • Co =/= CO, only the first letter is capital

8. Atoms are the Fundamental Components of Elements • Elemental Formula – How many atoms are bonded together in an element • Au = Gold ii. N2 = Nitrogen iii. Ni = Nickel • Seven Diatomic Elements: • Oxygen, Hydrogen, Nitrogen, Bromine, Chlorine, Iodine, Fluorine • How about diatomic oxygen vs. ozone, O3? • Are they the same? • No, BUT both are elemental forms of oxygen

9. Combining Elements to Form Compounds • Molecule- Consists of two or more atoms combined in a definite ratio • Compound– Atoms of different elements bound to one another • We had an Elemental Formula for elements, how will we represent chemicals bound together to form chemicalcompounds?

10. Combining Elements to Form Compounds • We had an Elemental Formula for elements, how will we represent chemicals bound together to form chemicalcompounds? • Chemical Formula – How much of what is in the compound (symbols and subscripts) • NaCl: One sodium per chlorine atom • MgCl2: One magnesium per two chlorine atoms

11. Combining Elements to Form Compounds • Hydrogen Sulfide is one of the smelliest compounds. Rotten eggs get their characteristic bad smell from the hydrogen sulfide that they release. Can you infer from this information that elemental sulfur is just as smelly? • *Compounds have Physical and Chemical properties that are different from the properties of their elemental compounds

12. Chemical Changes (rxn) • Remember, a change is chemical ONLY when the BONDS are BROKEN and reformed. • This process creates entirely new substances called ________________. • This change is NOT physical because you CANNOT GO BACK!! 

13. Chemical Changes • Compounds (several DIFFERENT elements together) can be broken down CHEMICALLY to their ELEMENTAL forms • Elemental forms are those consisting of ONLY one type of element • Ex: H2O  O2 + H2 (new elemental PRODUCTS were created)

14. Homework • Page 47-48, #32, 33, 34, 35, 37, 44, 45, 46 • Please do on a separate sheet and be ready to turn in for a grade (must have the assignment written on the top line and be neat!!)