Chemistry 20 Review - Introduction and Quick Review
Welcome to Classroom
The goal in this room is …. SUCCESS !!
As a team (student, parent, teacher) we will all work towards the achievement of this goal !
The expectations set out are there to help ensure that students can realistically reach this goal
If you have any questions or concerns, make an appointment with me and we can discuss
Do you have the skills ?
Let’s go over a few things that you need to make sure you have before you start this course
Scientific Knowledge
Scientific Knowledge is built on the results of countless ______ conducted by many investigators.
In order to find answers to questions in science, the scientific process must be ______, ______and ______.
A useful, ______ scientific investigation generally has all of the following parts
Introduction, Problem, Design, Data collection, Analysis and Conclusion.
** We will be discuss designing and reporting scientific investigations more later on **
Science deals with two types of knowledge:
Empirical Knowledge – this type of knowledge is ______. (facts)
Theoretical Knowledge – this type of knowledge is ______. (interpretations and theories)
Empirical (directly observable ) knowledge is considered more certain than interpretations or theoretical explanations.
Scientific Knowledge
Observations Versus Interpretations in Science
An observation is any report from your 5 senses. It doesnotinvolve an explanation. An observation can also involve measurements. Such an observation is a ______ one, as opposed to a ______one (no measurements).
An interpretation is an attempt to figure out what has been observed. Here are some examples designed to help you distinguish between them.
When doing labs, it is important not to confuse observations with interpretations. If you are asked to observe, you should not identify gases. “Hydrogen gas was produced when zinc was added to acid” is not an observation. What you see is the liquid getting cloudy with bubbles rising from the area surrounding the metal. The latter is what you should be reporting as an observation. Later if you collect the gas and it has hydrogen’s characteristic property, then it will be time to conclude that the bubbles contained hydrogen gas.
Precision, Error and Accuracy
A major component of the scientific inquiry process is the comparison of experimental results with predicted or accepted theoretical values.
All measurements have some degree of ______.
Uncertainty, often referred to as error , is not the result of a mistake necessarily, but can be caused by ______ of the equipment or experimenter.
______– describes the exactness and repeatability of a value or set of values.
______– describes the degree to which the result of an experiment or calculation approximates the true value.
Percent Difference & Percent Yield
______– determines how precise a set of measurements is. Compares experimental values to constants or theoretical values. (acceptable values for high school labs are ±10%.)
______– determines how close an actual(experimental) yield is to the predicted or theoretical value. (acceptable values for high school labs are >90%.)
Significant Digits
Examples
How many significant digits does each number have ??
1. 4568
2. 3.49
3. 0.0000862
4. 0.05009
5. 50.17
Significant Digits – Calculations Examples
How many significant digits would each answer have ??
Don’t forget to round properly
1. 5.3 + 7.62 – 3.298 =
2. 4.88 / 2.3 x 1.16 =
Scientific Notation
Used to ______ large numbers (and to clarify the number of significant digits), when reporting them and doing calculations.
MAKE SURE YOU CAN PUT THIS INTO YOUR CALCULATOR ACCURATELY!!!
Rules for Scientific Notation
If you want to make an exponent larger move the decimal to the left
If you want to make an exponent smaller move the decimal to the right
Scientific Notation Examples
1. 0.000000000523
2. 5110300000000000
Complete the following
1. 6.7 x 10 -4 + 3.3 x 10 -3 =
2. 4.6 x 10 7 - 2.1 x 10 5 =
3. (8.9 x 10 2) x (5.2 x 10 4 ) =
4. (4.4 x 10 8) / (1.2 x 10 3) =
SI Units
The International System of Units, ______, from the French Name, systéme international d’unites.
The measurement and communication system used ______ by scientists
Physical quantities are ultimately expressed in terms of 7 fundamental SI units, called ______All other quantities are derived from these units
SI Units – Base units Universality
SI Units – Prefixes Convenience
With the exception of centi-, we use prefixes that change by multiples of 1000
Tables and Graphs
Both tables and graphs are used to summarize information and to illustrate ______or ______.
It is important to prepare them ______, following accepted conventions, in order to best communicate the information.
Tables
1. All tables must have descriptive titles that mention both the manipulated and responding variables.
2. The row or column containing the manipulated variable precedes the responding
3. Headings of rows or columns are labelled with the units in parentheses where applicable and not included in the body of the table.
Graphs
1. Descriptive title (manipulated & responding variables are mentioned)
2. Labeled axes with units in parentheses
1. X-axis has the manipulated variable
2. Y-axis has the responding
3. Use appropriate scales, with equal increments, on the axes so the graph takes up at least ½ of the paper
4. Use a pen for data points
5. Draw, in pencil, a line of best fit if the data appears in to be in a straight line, if not use a smooth curve to connect the points
Interpolation
Finding a value between a set of data points
Extrapolation
Finding a value past a set of data points (dotted line)
Manipulating Formulas
Opposite Operation
What is done to one side must be done to the other.
Now down to the Chemistry Let’s get ready for Unit 1
Remember …
Chemistry is the physical science that deals with the composition, properties and changes in matter.
Classifying Matter
Matter: anything that has mass and takes up space.
Chemists can classify matter as solid, liquid, or gas. But there are other ways to classify matter, as well — such as pure substances and mixtures. Classification is one of the basic processes in science. All matter can be classified as either a pure substance or a mixture
PURE SUBSTANCES:
Apure substancehas a definite and constant composition — like water or sulfur. A pure substance can be either an element or a compound, but the composition of a pure substance doesn’t vary.
Pure substances have definite properties that are always the same (e.g. mp, bp, density, etc). You cannot distinguish a solution from a pure substance by looking at it, as they appear homogenous. There are two types of pure substances:
Elements:
are pure substances that cannot be broken down into simpler substances. They are the smallest particle that is the element. Empirical
They are composed of one type of atom (Theoretical), and are the building blocks of all compounds.
Each element has its own symbol, the first letter always being capitalized, and the second letter being lower case. Currently there are 118 different elements
*** Every element has very unique properties (i.e. (s), (l), (g), reactivity, density etc.).
Compounds:
are pure substances that contain two or more elements in definite proportions (fixed ratios) Theoretical
Compounds can be broken down into the elements they are made of. Empirical
Even though there are only 118 elements, there are millions of compound possibilities that can be formed from these elements.
Mixtures:
Mixturesare physical combinations of pure substances that have no definite or constant composition — the composition of a mixture varies according to who prepares the mixture.
Although chemists have a difficult time separating compounds into their specific elements, the different parts of a mixture can be easily separated by physical means, such as filtration or evaporation
Heterogeneous Mixtures:
aka Mechanical Mixtures have visible different parts (e.g. concrete, salt & pepper, soil, granola, chocolate chip cookies, etc.).
Homogeneous Mixtures
aka solutions are type of mixture where you only see one part. It appears to be one substance (e.g. soft drinks, clear tea, Kool-Aide, salt water, metal alloys, etc.) and cannot be easily distinguished from a pure substance without further testing.
Periodic Table
Dmitri Mendeleev created the periodic table in 1869
Periodic Law
Chemical & physical properties of elements repeat themselves in regular intervals when elements are arranged in order of increase atomic #
How its put together
Family (or Group): are the vertical columns on the periodic table numbered 1-18. Elements within a group have similar chemical properties to each other.
Periods: are the horizontal rows on the periodic table numbered 1-7. As you move left to right, you see an increase in the number of protons. On the far left we start with metals, and as we move farther to the right we end up in non-metals. Reactivity in metals usually decreases as we move to the right.
Atoms:
Atoms are the basic units of matter and the defining structure of elements. Atoms are made up of three particles: protons, neutrons and electrons.
Electrons are extremely lightweight and exist in a cloud orbiting the nucleus. The electron cloud has a radius 10,000 times greater than the nucleus
Atomic number:
represents the number of protons an atom contains. The atomic number is found in the top left corner of each element.
Atomic Mass:
is the mass of each element. This mass is made up of the number of protons plus the number of neutrons found in an atom (remember electrons have very little mass).
Isotopes:
Atoms of the same element that have a different number of neutrons.
IONS
Are atoms that have either lost or gained electrons in order to have a full outer shell of electrons.
Metals will lose electrons to become positively charged ions(CATIONS).
Non-metals will gain electrons to become negatively charged ions (ANIONS).
*** It is important to remember that electrons are negatively charged, so if an atoms gain electrons the charge becomes negative.
Bohr Model/Energy Level Diagram
Write # of protons and neutrons in the nucleus (or under a line)
Draw circles (or lines) to represent electron shells
Draw on Electrons
Remember:
2 – 8 – 8- 16
If there are more than 4 electrons there will be pairs
Bohr Model/Energy Level Diagram Examples
Diatomic Elements
Always in pairs. KNOW THESE!!!!
H2, N2, O2, F2, Cl2, Br2, I2
Polyatomic Elements
S8 and P4
Know these too! *This is SUPER important for writing and balancing chemical reaction equations*
Compounds
Ionic & Molecular Compound properties
Naming Ionic compounds
Naming Molecular compounds
Ionic Compounds
Ionic compounds are pure substances formed from a metal and a non-metal.
Ex. NaCl
All ionic compounds are solids at room temperature (High mp. And bp.)
When an ionic compound is dissolved in water, it will conduct electricity (because of the presence of charged particles)
Ionic Bond formed by the transfer of electrons creating ions that are attracted to each other
Example: Na + and Cl - NaCl
Molecular Compounds
Molecular compound- when two non-metals combine and electrons are shared
They can be solids, liquids or gases at room temperature
They tend to be insulators (poor conductors of electricity) even in solutions, because there are no IONS in MC
Have low melting and boiling points
Names and Formulas
The chemical formula of an element or compound indicates which elements and how much of each one is present in a compound.
Chemical nomenclature is the systematic method of naming substances
Ex. table salt has the chemical name sodium chloride and its formula is NaCl.
International Union of Pure and Applied Chemistry
IUPAC for short
The governing body for scientific communication which specifies rules for chemical names and symbols (**Remember the universality of science )
These are the rules we follow for naming all elements and compounds.
Naming Ionic Compounds
When you have a chemical formula
LiF(s) MgCl2 (s) FeS(s) Fe2S3 (s)
1. Identify the metal first, and name
Check the periodic table to see if the metal is multivalent (more than one ion charge)
If not move on, if it is use subscripts to determine which charge and use roman numerals between the names
2. Name the non-metal second
The name of the non-metal changes its ending to –ide
**In high school chemistry, we name BINARY COMPOUNDS, so there is only one cation and one anion**
When you have a chemical formula
LiF(s)
MgCl2 (s)
FeS(s)
Fe2S3 (s)
Polyatomic Ions
Polyatomic ions are groups of atoms acting as one. Ex. Carbon and oxygen can act as one - CO32-
Polyatomic ions are composed of two or more elements covalently bonded with an overall negative or positive charge.
These are found on your periodic table.
This table is found on the back of your periodic table, and is used as a reference for you to help identify them in the compounds.
Polyatomic Ions - Examples
NaCH3COO (s) –
K2Cr2O7 (s) –
MnHPO4 (s) –
Steps to writing formulas
1. Write the metal ION symbol with its ion charge. Next to it write the non-metal elements symbol with its ion charge.
Ex. Ca2+ Cl-
2. Balance the ION charges to ZERO.
There must be two chlorine atoms each with an ion charge of 1- to balance the 2+ ion charge of one calcium atom.