Language of substances

1. Language of substances • Classification of matter • Properties of matter • Element groupings

2. Classification of matter: degree of uniformity Heterogeneous matter: sample is not uniform throughout Homogeneous matter: sample is uniform throughout We will expand this classification scheme of matter significantly in the days ahead. Note that the degree of uniformity is completely dependent upon the scale upon which the sample is viewed.

3. Element: matter that cannot be chemically or physically broken down into simpler substances Chemists abbreviate elements with one, two, or three letter symbols, most of which are relatively obvious. Some, however, only make sense in other languages. Elements display certain properties. But before we can explore them, we must establish a language of properties.

4. Intensive properties: do not depend upon size of sample Extensive properties: do depend upon size of sample

5. PhysicalPropertiescan be determined without changing the chemical makeup of the sample. • Some typical physical properties are: • Melting Point, Boiling Point, Density, Mass, Touch, Taste, Temperature, Size, Color, Hardness, Conductivity. • Some typical physical changes are: • Melting, Freezing, Boiling, Condensation, Evaporation, Dissolving, Stretching, Bending, Breaking.

6. Chemical Propertiesare those that do change the chemical makeup of the sample. • Some typical chemical properties are: • Burning, Cooking, Rusting, Color change, Souring of milk, Ripening of fruit, Browning of apples, Taking a photograph, Digesting food. • Note: Chemical properties are actually chemical changes.

7. Periodic Table: a visual organization of all the elements that highlights similarities in properties or organized progression in properties • Periods:The seven horizontal rows of the periodic table. • Groups: The 18 vertical columns of the periodic table. The periodic table is a vast storehouse of information. You would be wise to make it your friend. There are very few topics we will cover that will not become easier with Competent use of the periodic table.

8. Main Groups: • s-block elements: Two groups on the left (1 & 2) • p-block elements: Six groups on the right (13–18) • Transition Metal Groups: • d-block elements: Ten groups in the middle (3–12) • f-block elements: Fourteen groups between 3 & 4 are called inner transition metals.

9. Metals: Found on left side of periodic table. Nonmetals: Found on the right side of periodic table. Semimetals: Form a zigzag line at the boundary between metals and nonmetals.

10. SI Units: prefix + unit

11. Scientific Notation Scientific Notation and SI: hand in glove Example From Table 1.4 (p.11): pico (abbrev. as “p”) = 10-12 so 1pA = 1* 10-12 A To eliminate a metric prefix, replace the prefix with its mathematical factor.

12. Temperature Celsius to Fahrenheit Fahrenheit to Celsius To convert from Celsius to Kelvins, add 273.15 to the degrees Celsius and change units to Kelvins. To convert from Fahrenheit to Kelvins, first conver to Celsius and then convert to Kelvins.

13. Volume

14. Density Density is a ratio of mass to volume. It can be used to change knowledge of one into knowledge of the other.

15. Accuracy and Precision Accuracy refers to the degree to which the measurements match a “correct” value. Precision refers to the degree of closeness between the measurements. Comprehension question

16. Watch the zeroes!!! 00.0007805900 leading zeroes interior zeroes trailing zeroes Significant figures is, at heart, a topic for labs. In a lab, it is a set of rules for establishing how much “credit” you get for a given measurement. In the lecture hall, it is a set of rules for limiting the output of calculators. Significant Figures1. Counting sig figs In scientific notation, all of the number part (not the exponent part) are sig figs.

17. Significant Figures2. Math with sig figs Multiplication and Division: Answer has same # sig figs as number with FEWESTsig figs Addition and subtraction: Answer has same # digits to the right of the decimal as number with FEWEST # digits there (# sig figs can change!!!) Exponents and logs: Don’t ask, don’t tell.

18. Factor-Label Method Creating conversion factors: Using conversion factors: Comprehension question

19. Practice your skills • 1 nautical mile is the distance something travels in one hour if they are travelling at 1 knot. • A knot (in practice) is 47 feet and 3 inches in 28 seconds. • How many feet are in one nautical mile? • How many meters? (1” = 2.54 cm)

20. Solution First, convert knot into a rate with familiar units Then convert that rate into a distance per hour. Given that 1 nautical mile is the distance travelled at 1 knot in one hour, One nautical mile is 6075 feet (or 1852 meters).

21. Factor-Label Method #1: Conversion Factors Conversion factors are fractions in which the numerator and denominator have different units • Problem-solving technique that focuses on doing math that makes the units correct • The most key skill in this technique is the ability to create and use conversion factors • Conversion factors are (1) created from equalities and (2) found in all derived units (material properties) From your exams: Non-SI Unit Equivalencies 1 inch = 2.54 cm 1 pound = 0.4535924 kg 1 ounce (mass) = 28.3495 kg 1 cal = 4.184 J 1 BTU = 1055.06 J 1 hp = 745.700 W 1760 yd = 1 mi 1 L = 1.057 qt 16 oz (mass) = 1 lb Conversion Factors or Diamond has a density of 3.513 g/mL or

22. You want Works as well Because Sometimes you cannot get a conversion in a single step—multiple-step conversion work like this: A A C A C A B C B C B B x = Factor-Label Method #2: unit cancellation The units are a mathematical entity just like a number and can be multiplied, divided, and cancelled just like numbers too. Just like you would: you can also: So, to convert from unit “X” to unit “Y” you need to create a conversion factor that allows you to cancel the “X” you already have and add a “Y” unit you don’t have. Comprehension questions