Gen Chem Chapters 1-3 Exam

Chemistry is the study of?

Matter and its Properties

What is Matter?

Anything that has mass and takes up space. Basically they physical material that is all around us.

What are Properties?

Properties of matter are characteristics that help us identify the substance. These include: size, color, flammability, reactivity.

What are physical properties of matter?

displayed without a change in chemical composition. such as:

• temperature where phases changes occur (boiling point, melting point, sublimation point)

• color

• odor

• size

• density

• malleability and ductility

• compressibility

What are chemical properties of matter?

displayed during a chemical change (change in composition). such as:

• flammability

• stability

• acidity

• toxicity

• corrosiveness

What are Physical Properties?

Characteristics of matter that are not associated with the matter changing chemical composition. Such as:

• Color

• Odor

• Size

• Density

• Temperature

• Electrical Conductivity

• Boiling Point

• Freezing Point

What are Physical Changes?

Changes that can occur to matter that do NOT affect the chemical nature of the matter. Such as:

• Freezing

• Melting

• Dissolving

• Cutting up the objects into smaller pieces

• Warming or cooling the object

• Changing the objects shape

NOTE!!

SOME Physical Properties are not observed unless the substance is undergoing a Physical CHANGE

What are Chemical Properties?

Characteristics of matter that are displayed when matter changing chemical composition. Such as:

• Flammability

• Reactivity

• Stability

• Acidity

• Temperature of thermal decomposition

What are Chemical Changes?

Changes that ALWAYS result in one or more types of matter that are different than what you had before. Such as:

• Burning

• Chemical Reaction

• Wait until decomposition occurs spontaneously

• Heat added until decomposition noted

Physical Properties:

• Red

• Shiney

• Density (slightly less dense than water)

• 85% is water

Physical Changes:

• Dehydrating

• Cutting

• Juicing

Chemical Properties:

• Easily Oxidized

• Rots Quickly

• Flammable

• Acidic

Chemical Changes:

• Oxidation

• Burns after water is removed

• Reacts with bases to neutralize them

States of Matter (Physical Property)

• Solid

• Liquid

• Gas

States of Matter: SOLID

Molecular Spacing:

• Very closely spaced

• Molecules DO NOT move past each other

Compressible?

• NO

Flow? (Assume Shape of Container?)

• NO

States of Matter: LIQUID

Molecular Spacing:

• Very closely spaced

• Molecules DO move past each other (packed jr. high hallway)

Compressible?

• NO

Flow? (Assume Shape of Container?)

• YES

States of Matter: GAS

Molecular Spacing:

• Widely spaced

• Molecules move independently (kansas)

Compressible?

• YES

Flow? (Assume Shape of Container?)

• YES

Classifying Matter by Composition

Classifying matter based on its composition involves categorizing substances into pure substances, which can be elements or compounds, and mixtures, which can be homogeneous or heterogeneous.

Pure Substance (Element and Compound)

• Contains only one type of atom

• Diatomic elements are still considered elemental

• P4, O3, S8

• Need a nuclear reactor to break down further

Pure Substance (Compound)

• Contains more than one type of atom, but the atoms must be separated through chemical means

• Each unit in this substance is the same, with the same atoms bonded in the same way

Mixtures (Homogeneous and Heterogeneous)

Homogeneous:

• Mixed on the molecular level

• Same composition throughout

• EX (Saltwater, Air, Vinegar, Steel, Black Coffee)

Heterogeneous:

• Often, you can see the components

• Composition varies from one area to another

• EX (Oil and Water, Salad, Chicken Noodle Soup, Sand and Water, Pizza)

Homogeneous Mixture: Aqueous Solution

• Awuenous (aq): Dissolved in water

What are the differences in components?

State of matter (solid and liquid)

NOTE!!

All substances of the same state will stay together. You may still need to separate further to get to pure substances/

Chemical Notation

Elements are identified by their symbols which are one or two letters long.

• The first letter is ALWAYS capitalized and is the ONLY letter capitalized in a chemical symbol

• Elements bond together to form compounds

• The compound will have unique chemical and physical properties

Writing Reactions

Reactants → Products (Read this arrow as “yields” or “forms”)

Chemical: CH4(g) + 02(g) → CO2(g) + H20(g)

Physical: (physical changes are also sometimes described using reactions)

• H20(I) → H20(g) = boiling

• H20(I) → H20(s) = freezing

• C6H12O6(s) → C6H12O6 (aq) = dissolving

The importance of units

The unit is just as important as the number you report!

Scientific Notation

Large numbers in standard notation always have POSITIVE EXPONENTS:

• 4,605 = 4.605 × 10³

• 46,052,222 = 4.6052222 × 10^7

Small numbers in standard notation always have NEGATIVE EXPONENTS:

• .0258 = 2.58 × 10^-2

• .0000258 = 2.58 × 10^-5

Prefixes and Scientific Notation

Often, we use a prefix in front of a metric unit to replace the “x10” part of a large or small number. For example:

• 14 × 10³ g → 14 kg

• 14 × 10^-6 g → 14 μg

• 14 × 10^-3 g → 14 mg

Note: the portion of the number in green is directly replaced by the symbol for the prefix

Prefixes you need to memorize!!

• We will begin to use these prefixes to MAKE unit conversion factors!

• The most important concept that I can pass to you is that the letter literally is a placeholder for the number given.

• “kilo” is code for “times ten to the third” when you see it used with a unit.

What is temperature?

Temperature is a measure of the average kinetic energy of a sample.

What is Absolute Zero?

Absolute Zero is the coldest temperature possible. It is where all motion ceases. A lower temperature cannot exist.

Temperature

• Not only are the temperatures different, but the size of a degree is different for celsius and fahrenheit

• In contrast, the size of a Kelvin is the same as a degree Celcius

Derived Units

• Units formed by multiplying or dividing basic SI units

• Volume (distance³): cm³ m³ ft³

• 1 dm³ = 1 cm³

• Speed (distance/time): m/s mi/hr km/hr

60 mi/hr → 60 mi = 1hr

234 m/s → 234m = 1s

• Density (mass/volume): g/cm³ kg/L kg/m³

.862 g/cm³ → .862g = 1cm³

2.3 kg/L → 2.3 kg = 1L

Sig Fig Rules:

1. All nonzero digits ARE significant

2. Zeros

   1. Interior zeros ARE significant

   2. Leading zeros ARE NOT significant

   3. Trailing zeros ARE significant IF they are after a decimal point

3. Exact numbers (counted, or integral numbers used in an equation) have infinite sig figs.

Sig Fig Math:

1. In Multiplication of Division, the result carries the same number of sig figs as the factore with the least

2. In add/subtract, the result carries the same number of decimal places as the quantity with the fewest decimal places.

Rounding

1. When rounding, round up if the digit dropped is 5 or more

2. Avoid rounding errors by rounding only the final answer

Dimensional Analysis:

1. Simple: Where the conversion factors are given

2. Metric/Prefix: Still pretty simple, but the conversion factors are built by you from the prefixes you memorized

3. Derived Units: How to use a derived unit as a conversion factor. Also, how to conver one set of derived units to another

4. From word problems. Here, you use the words in the problem to build conversion factors to use.

Modern Atomic Theory (model of nature that explains those laws)

1. All matter is composed of atoms

2. All atoms of a given element share the same chemical properties that are unique to that element

3. Atoms combine in simple, whole number ratios to form compounds

4. Atoms of one element cannot change into atoms of a different element

   1. In a chemical reaction, atoms only change the way that they are bound to each other, the atoms themselves do not change.

Subatomic Particles (modern): PROTONS

• POSITIVE charge

• Relatively large mass

• Located in nucleus

• Determines the elemental identity of the atom

Subatomic Particles (modern): NEUTRONS

• NO charge

• Relatively large mass (Almost the same as the proton)

• Also located in nucleus

• (Isotopes)

Subatomic Particles (modern): ELECTRONS

• NEGATIVE charge (Charge is the same magnitude as the proton, but opposite sign)

• Very small mass compared to proton and neutron

• Located outside of the nucleus

AMU (Atomic Mass Units)

A unit that was invented to deal with the very small masses of subatomic particles. It was defined as 1/12 of the mass of a carbon atom (with 6 protons and 6 neutrons)

Atomic Theory:

• The protons and neutrons are packed closely together in a dense core called the NUCLUES

• Surrounding the nucleus, the electrons move about rapidly through a large volume of space

Atomic Theory: Electrical Charge

• Opposite electrical charges attract each other

  • The negative charged electrons are held near the positively charged nucleus

• Like charges repel each other

  • The electrons try to get as far away from one another as possible

Atomic Number & Mass Number

Atomic Number: Z = Number of protons in all atoms of that element

Mass Number: A = Number of protons AND neutrons

What are Isotopes?

• Atoms with the same atomic number but different masses are called ISOTOPES

• Since the chemical behavior of atoms is determined by electrostatic attraction between the nuclei and the electrons, atoms with the same number of protons (Z) behave identically

Isotope Symbol:

Mass Number = Number of Protons + Number of Neutrons

Atomic Number = Number of Protons

Atomic Mass:

• Atoms have measurable masses

• The Atomic Mass of an element is the average mass of an atom of the element

Isotopes Mart the Spot

Ratios of stable isotopes help locate the origin of corpses, follow migration routes, and authenticate items as different as bottled water and expensive cheese

Monatomic Ions:

• Ions are atoms or groups of atoms with electric charge

• CATIONS: have a POSITIVE charge

• ANIONS: have a NEGATIVE charge

Because removing protons would change the atom’s identity, when we form ions, we are implying that the number of electrons in the atoms is changing

Elements that exists as diatomic or Triatomic Molecules

The Periodic Table of Elements (Dmitri Mendeleev)

A Simple Periodic Table

Periodicity

Periodicity: Note how the pattern of this plot repeats for each “Period” or row of the periodic table

Electron Configuration: How are electrons distributed in an atom?

Elements That Forms Ions with Predictable Charges