Chapter 18 Section 1

1. Chapter 18 Section 1 Composition of Matter

2. Pure Substances • A type of matter with a fixed composition • Can be either an element or compound • Examples • Helium • Aluminum • Water • Salt

3. Elements • All atoms in the substance are the same identity • About 90 elements are found on Earth • More than 20 others have been made in labs • Usually unstable • Exist for a short period of time

4. Diamond Mine South Africa

5. Background • Ancient Greeks thought everything derived from 4 elements: fire, earth, air and water • In the 1600’s chemists realized those were not elements like the ones we know now: carbon, gold, silver, copper, lead, tin, sulfur, mercury, and iron. • But what did they have in common with each other?

6. Dmitri Mendeleev: 1869 • Russian scientist developed the modern Periodic Table with 63 known elements. • Collected information on element properties and grouped elements by their: • Atomic mass • Physical and Chemical properties • He noticed a periodic pattern (periodic means repeating)

7. First Periodic Table • The 63 known elements were NOTfirst 63 in the Periodic Table. Some were missing! • He put elements in similar groups and left blanksin the table where he predicted that new elements would be found and placed. • He even used the patterns in the table to predict the properties of the new elements. • Later scientists proved he was right!

8. Mendeleev’s Table

10. Modern Periodic Table • Everything is made from only 115 elements. • Elements represented by a symbol, either • One uppercase letter, like C for carbon, or • An uppercase and lowercase, like Cu for copper

11. Families or Groups • There are several “families” or groups: • Non-metals - Alkali metals • Alkaline earth metals - Transition metals • Rare earth metals • Other metals • Halogens • Noble gases

12. Label Your Periodic Table - 1 • Label the groups (columns) as 1-18 at the top • Label the periods (rows) as 1-7 down the left. • Using a dark color, draw a zig-zag staircase line dividing metals from non-metals. • Left of B, between B & Al, between Al & Si, between Si & Ge, between Ge & As, between As & Sb, between Sb & Te, between Te & Po, between Po & At • Draw circles around Br (35), Hg (80), and UUB (112). These are liquids at room temperature.

13. Label Your Periodic Table - 2 Label Oxidation Numbers above columns: • Above column 1 put +1 -> Label columns 1 and 2 as • Above column 2 put +2 Most Reactive Metals • Above column 13 put +3 -> Label columns • Above column 14 put +/- 4 3 through 16 as • Above column 15 put -3 Middle Reactive • Above column 16 put -2 • Above column 17 put -1 -> Most Reactive Non-Metals • Above column 18 put 0 -> Label as Least Reactive

14. Color Your Periodic Table - 1 • Color H & above zigzag line Light Green label these Non-Metals • Color the rest of column 1 Dark Blue, label these Alkali Metals • Color column 2 Red, label these as Alkaline Earth Metals • Color columns 3-12 Light Blue, label as Transition Metals

15. Color Your Periodic Table - 2 • Color below zigzag line Purple, label as Other Metals • Color column 17 Orange, label these as Halogens • Color column 18 Dark Green, label as Noble Gases • Color bottom two rows Gray, label as Rare Earth Metals

16. Solid, Liquid, or Gas • Most elements are solid at room temperature. Their symbols are shaded black. • The 11 elements that are gases tend to be at the top right corner of the table. Their symbols are shaded white. • 3 elements are liquid at room temperature. Their symbols are shaded gray.

17. Reactivity • React:when elements combine chemically • Elements likely to combine= highly reactive, so they will react with other substances. • The least reactive elements are the noble gases in the far right column. • Most reactive metals are two left columns • The most reactive non-metals are in the halogen family in column 17.

18. Compounds • A substance in which two or more elements are combined in a fixed proportion • Examples • H2O • NaCl

19. Forming Compounds • The 118 elements form millions of compounds. • This is similar to how many words in the dictionary are formed from just 26 letters. • Compounds and their elements have different properties. H2O is different than elements H or O.

20. Molecules • Substance consisting of two or more atoms that are bonded together • Elements or Compounds • Examples • H2O2 • O2 • Diatomic, or 2- atom molecule

21. Mixtures • A material made up of two or more substances that can be easily separated by physical means • Examples • Pop • Pizza • Chicken Noodle Soup

22. Heterogeneous Mixtures • Mixture in which different materials can be distinguished easily • Examples • Granite • Dry soup mixtures • Trail mix • Candy bowl

23. Homogenous Mixtures • Two or more substances blended evenly throughout • Remains constantly and uniformly mixed • Examples • Pop • Kool Aid • Jello

24. Colloids • A type of mixture with particles larger then the solution, but not large enough to settle • Example • Milk • Paint • Detecting Colloids • Tyndall Effect • The scattering of light by colloidal particles

25. Suspensions • Heterogeneous mixture containing a liquid in which visible particles settle. • Example • Pond Water

26. Ch 18.1 Composition Analysis(answer in 1 paragraph each) • How is a compound similar to a homogeneous mixture? Different? • Distinguish between a substance and a mixture. Give 2 examples of each. • Describe differences between colloids and suspensions. • How do the words “Shake well before using” tell that juice is a suspension? • If a fabric is 90% cotton and has a mass of 500g what is the cotton mass?

27. Chapter 18 Section 2 Properties of Matter

28. Physical Properties • Any characteristic that you can observe without changing the identity of the substance • Color • Size • Shape • Density • Melting Point • Boiling Point • Behavior

29. What Physical Properties can you use to describe the following?

30. Separating using physical properties • Sifting • Evaporation • Magnet

31. Physical Changes • The identity remains the same • Physical changes are changes in shape, size or state of matter • You use physical change to separate • Distillation • Evaporating a liquid and recondensing it

32. Chemical Properties • Characteristic of substance that can indicate whether it can undergo a certain chemical change • Flammability • Changes when exposed to light

33. Chemical Changes • A change of one substance into another • You cannot change the substance back without chemical means. • Chemically combine hydrogen gas with oxygen gas to make H2O, or liquid water.

34. Detecting Chemical Changes • Heat • Cooling • Bubbles • Formation of a precipitate

35. Conservation of Mass • Mass of all substances before chemical change equals mass of all substances that remain after the change.

36. Ch 18.2 Properties Analysis(answer in 1 paragraph each) • Explain why water evaporation is a physical change, not a chemical one. • List 4 physical properties for liquids. • Explain why flammability is a chemical property and not a physical property. • Explain how the law of conservation of mass applies to chemical changes.