Chemistry Skills and Reasoning Weeks 1 and 2
Chemistry Skills and Reasoning Weeks 1 and 2 CHM1040
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This 3 page Class Notes was uploaded by Freya Kniaz on Monday September 12, 2016. The Class Notes belongs to CHM1040 at Wayne State University taught by Dr. Andrea Matti in Fall 2016. Since its upload, it has received 32 views. For similar materials see Chemistry Skills and Reasoning in Chemistry at Wayne State University.
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Date Created: 09/12/16
Chemistry 1040 Week 1 Lecture Notes Chapter One: Introduction • Chemistry is important, it is the central science • Chemistry: the science of materials and their changes • ScientificApproach: make an observation, formulate a hypothesis, do an experiment • Theory: we are attempting to explain why something happens • Law: tell what happens Chapter Two: Data and Measurements • ancients used body parts to measure (that is where we get foot, inch, etc.) • strange measurements: banana equivalent (amount of radiation you receive from one banana) or beard second (how much your beard grows in one second) • It takes 744 points to get anAin this class (that is a measurement!) • Parts of a quantitative observation: number and unit • Scientific Notation: the base number must be between 1 and 10; the exponent is negative if you move it to the right, positive if you move it to the left • 1 mL = 1 cm ; 1L = 1 dm 3 • Nonzero integers are always significant figures (ex.: 32, 451, 9, or 1798926391) • Leading zeros are NEVER significant figures (ex.: 3000 or 0.0024) • Captivated or trailing zeros areALWAYS significant figures (ex.: 304 or 2.40) Chapter Three: Matter • Matter: anything occupying space and having mass • Types of matter: solid, liquid, gas, and plasma • Solids are rigid and have a fixed volume and shape • Liquids have a definite volume and assume the shape of the container • Gases have no fixed volume or shape; it also takes the shape of its container • Matter undergoes undergoes two types of changes: chemical and physical • Physical change: a change observed without changing its chemical composition; changes to a feature that is unique to the substance such as odor, color, volume, state (s, l, g), boiling or melting point • Chemical change: a change in the chemical composition of a subtance(s), generally forms a new substance(s) (examples: flammability, rust of steel, digestion of food) • Composition generally changes as a result of contact with other matter or the influence of energy • Best way to tell if physical change or chemical is to look at a chemical formula • Element: substance that cannot be broken down into other substances by chemical method • Compound: substance composed of a given combination of elements that can be broken down into those elements by chemical methods • A compound always contains atoms of different elements and always has the same compositions • Homogenous: cannot tell the difference between the parts, they are equally distributed (ex.: air around you, brass, salt stirred into water) • Heterogeneous: can tell the difference between the parts, they are not equally distributed (ex.: oil and vinegar dressing, sand stirred into water) • Mixture can be separated based on different physical properties of the components ◦ Boiling Point → Distillation ◦ State → Filtration ◦ Adherence to surface → Chromatography ◦ Votality → Evaporation Chapter Four • Most elements come from stars but some were made in by scientists • Memorize the periodic table → the names and symbols • Most natural materials are a mixtures of pure substances • Pure substances are either elements or combinations of elements called compounds • Law of Constant Composition: a given compound always has the same composition, regardless of where it comes from • Conservation ofAtoms: atoms are neither created nor destroyed • Atoms are composed of a protons, neutrons, and electrons • Dalton'sAtomic Theory ◦ All atoms of a given element are identical (not necessarily true → isotopes) ◦ The atoms of a given element are different from those of any other element ◦ Atoms of one element can combine with atoms of other elements to form compounds.A given compound always has the same relative numbers and types of atoms ◦ Atoms are indivisible in chemical properties (neither created nor destroyed), it simply changes the way they are grouped together • Chemical formulas describe compounds • Chemical formula: expresses the types of atoms and numbers of each type in each unit (molecule) of a given compound • J.J. Thomas postulated the existence of electrons using cathode ray tubes; plum pudding model ◦ the atom must also contain positive particles that balance exactly the negative charge carried by particles that we now call electrons • Ernest Rutherford explained the nuclear atom ◦ atom has a dense center of positive charge called nucleus ◦ electrons travel around the nucleus at a relatively large distance ◦ a proton has the same magnitude of charge as the electron, but it is positive • Rutherford and Chadwick → most nuclei also contain a neutral particle called the neutron ◦ neutron is slightly more massive than proton but has no charge ◦ finally described the nuclear atom • Electrons are found outside the nucleus ( - charge) • Protons are found in the nucleus (+ charge) • Neutrons are found in the nucleus (no charge) • Nucleus is small compared with over all size of the atom, extremely densel accounts for almost all of atom's mass • CHEMISTRY OFANATOMARISES FROM ITS ELECTRONS • Electrons are the part of the atom that “intermingle” • The number of electrons really determines an atom's chemical behavior • Isotopes: atoms with the same number of protons but a different number of neutrons • Isotopes show almost identical chemical properties because the chemistry of an atom is due to its electrons • In nature most elements contain mixtures of isotopes
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