Unit 1/2

MEASUREMENT

Accuracy –how close a measurement is to the accepted value

Precision–how close a series of measurements are to each other

Significant Figures

Indicate precision of a measurement.

Recording Sig Figs

Sig figs in a measurement include the known digits plus a final estimated digit

Counting Sig Figs

Count all numbers EXCEPT:Leading zeros -- 0.0025

Practice

Calculating with Sig Figs

Multiply/Divide - The # in the question with the fewest sig figs determines the # of sig figs in the answer.

Add/Subtract - The # with the lowest decimal value determines the place of the last sig fig in the answer.

Exact Numbersdo not limit the # of sig figs in the answer.

Counting numbers: 12 students

Exact conversions: 1 m = 100 cm

“1” in any conversion: 1 in = 2.54 cm

Practice Problems

Scientific Notation

Converting into Sci. Notation:

Move decimal until there’s 1 digit to its left.

Places moved = exponent.

Large # (>1)  positive exponent
Small # (<1)  negative exponent

Only include sig figs.

Practice Problems

1. 2,400,000 g

2. 0.00256 kg

3.7  10-5 km

4.6.2  104 mm

Calculating with Sci. Notation

(5.44 × 107 g) ÷ (8.1 × 104 mol) =

Notice

We can only add and subtract numbers with the same units

However, when we divide the units are divided and when we multiply the units are multiplied.

Ex: 100km / 1 hour = 100km/hr

ex: 5.0m * 2.0m = 10m2

Unit Conversions

  1. Find the difference between the exponents of the two prefixes.
  2. Move the decimal that many places.

Practice Problems

1) 20 cm = ______m

2) 0.032 L = ______mL

3) 45 m = ______nm

4) 805 dm = ______km

Dimensional Analysis

The “Factor-Label” Method

Units, or “labels” are canceled, or “factored” out

Steps:

Identify starting & ending units.

Line up conversion factors so units cancel. (conversion factor = need/got)

Multiply conversion factor by given amount

Check units & answer

Practice Problems:

  1. How many milliliters are in 0.946 L of milk?
  1. Your European hairdresser wants to cut your hair 8.0 cm shorter. How many inches will he be cutting off?
  1. A piece of wire is 1.3 m long. How many 1.5-cm pieces can be cut from this wire?

Section 1.1: Science and Technology
Outcomes:
C1.1k / recall the categories of pure substances and mixtures and explain the nature of homogeneous mixtures
A1.2sts / explain that scientific knowledge and theories develop through hypotheses, collection of evidence through experimentation, and the ability to provide explanations

Chemistry:

Observation:

Interpretation:

Types of Knowledge:

Lesson 1: The Atomic Theory

I can outline the role of evidence in the development of the atomic model consisting of protons and neutrons (nucleons) and electrons; i.e., Dalton, Thomson, Rutherford, Bohr.

Dalton:

-Atoms cannot be created nor destroyed

-Atoms are constantly moving

Thomson:

-Atoms have electrons

-e- are extremely tiny compared to the size of an atom

-chocolate chip cookie

Rutherford:

-nucleus exists with protons (p+) in it

-nucleus is majority of mass

-e- orbit around the nucleus

Bohr:

-Electrons exist in stable energy levels around the nucleus

Lesson 2: The Atom

I can describe the basic particles that make up the underlying structure of matter, and investigate related technologies.

Nucleons:

Nuclear Notation & Isotopes

Elements from the periodic table:

Isotopes:

** Elements often have 2 or more isotopes*

Atomic Number: (Identifies the element)

Mass Number: (Identifies the isotope)

**For atoms, the number of protons (p+) = the number of electrons (e-)

To calculate the number of neutrons:

Lesson 3: The Periodic Table

I can explain, using the periodic table, how elements combine to form compounds, and follow IUPAC guidelines for naming ionic compounds and simple molecular compounds.

Groups are VERTICAL columns.

Periods are HORIZONTAL rows.

Group 1: Alkali Metals

Group 2: Alkaline Earth Metals

Group 17: Halogens

Group 18: Noble Gases

Alkali Metals:

Alkaline Earth Metals:

Halogens:

Noble Gases:

Metals:

Non-metals:

Metalloids:

Energy Level Diagrams (BOHR)

*Electrons exist in fixed energy levels

*Each energy level can hold a certain number of electrons.

Period Number= # of energy levels

Ex. Nitrogen has 2 energy levels, it is located in the second period

Definition:

VALENCE ELECTRONS: Electrons in the outermost energy level. They are the electrons that react.

Group #= # of valence electrons

Ex. Nitrogen has 5 valence electrons and is located in group 5

Ex. Magnesium has 2 valence electrons and is located in group 2

Lesson 4: Electron Dot Diagrams

I can explain, using the periodic table, how elements combine to form compounds, and follow IUPAC guidelines for naming ionic compounds and simple molecular compounds.

Electron dot diagrams are a useful way to represent an atom and its valence electrons.

Ex. Lithium has 1 valence electron (v.e), since it is in group 1, so the electron dot diagram for Li looks like:

Rules for creating an electron dot diagram:

  1. Place a dot (represents an electron) on any side of the element symbol.
  2. When an element has more than 4 dots (v.e.), begin to arrange the dots in two’s.

** There is no rule for where to place the first dot**

Lesson 5: The Formation of Ions

I can explain, using the periodic table, how elements combine to form compounds, and follow IUPAC guidelines for naming ionic compounds and simple molecular compounds.

An ATOM has the same number of protons and electrons.

Ex. H, Li, B, BeATOMS are neutral (they don’t have a charge)

An ION does NOT have the same number of protons and electrons.

Ex. IONS have a (+) or (-) charge

CATIONS have a (+) charge / ANIONS have a (-) charge
-They are metals / -They are non-metals
-More p+ than e- / -More e- than p+
-Names stay the same / -Name changes to end in “-ide”
Ex. Lithium ion, Magnesium ion / Ex. Oxide, Chloride

Ions do not form in isolation… they form COMPOUNDS.

-Metals give up electrons (that’s why they have a positive charge)

-Non-metals either accept or share electrons

Lesson 6: Forming Compounds

I can predict formulas and write names for ionic and molecular compounds and common acids.

The Ionic Compounds

Metals react with a non-metal

Electrons transfer from the metal to the non-metal

Ions are held in place by ionic bonds.

Naming Ionic Compounds

Rules:

  1. Write down the name of the cation (metal) first.
  2. Write down the name of the anion (non-metal) last.
  3. Change the ending of the anion to –ide.

MolecularCompounds

Non-metals share electrons.

Form covalent bonds.

Naming Molecular Compounds

Rules:

  1. Remove the ending of the second element, and add "ide" just like in ionic compounds.
  2. When naming molecular compounds prefixes are used to dictate the number of a given element present in the compound. " mono-" indicates one, "di-" indicates two, "tri-" is three, "tetra-" is four, "penta-" is five, and "hexa-" is six, "hepta-" is seven, "octo-" is eight, "nona-" is nine, and "deca" is ten.
  3. If there is only one of the first element, you can drop the prefix. For example, CO is carbon monoxide, not monocarbon monoxide.
  4. If there are two vowels in a row that sound the same once the prefix is added (they "conflict"), the extra vowel on the end of the prefix is removed. For example, oneoxygenwould be monooxide, but instead it's monoxide. The extra o is dropped.