CHEM 101 FIRST WEEK NOTES
CHEM 101 FIRST WEEK NOTES Ch 101
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This 5 page Class Notes was uploaded by Lauren Faris on Friday September 30, 2016. The Class Notes belongs to Ch 101 at University of Alabama - Tuscaloosa taught by Dr. Bakker in Fall 2016. Since its upload, it has received 54 views. For similar materials see Chemistry 101 008 in Science at University of Alabama - Tuscaloosa.
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Date Created: 09/30/16
CHEM 101 FIRST WEEK NOTES VERY BRIEF REVIEW By Lauren Faris Chapter 1 Cliff Notes Matter is composed of particles (neutrons, protons, and electrons, atoms, and molecules), and is defined as anything that has mass and occupies space. Atoms are basic submicroscopic particles that constitute the fundamental building blocks of ordinary matter. Molecules are substances formed when two or more atoms come together (bond) in specific geometric arrangements. In solid matter, atoms or molecules pack close to each other in fixed locations. In liquid matter, atoms or molecules pack about as closely as they do in solid matter, but they are free to move relative to each other. In gaseous matter, atoms or molecules have a lot of space between them. o These qualities make gases compressible. A pure substance is made up of only one component, and its composition is invariant. o Elements: An element is a substance that cannot be chemically broken down into simpler substances. o Compounds: A compound is a substance composed of two or more elements in fixed definite proportions. A mixture, by contrast, is a substance composed of two or more components in proportions that can vary from one sample to another. o Heterogeneous mixtures: A heterogeneous mixture is one in which the composition varies from one region of the mixture to another. Made of multiple substances, whose presence can be seen (example: a salt and sand mixture). o Homogeneous mixtures: A homogeneous mixture is one made of multiple substances, but it appears to be one substance. All portions of a sample have the same composition and properties (like sweetened tea). Scientific Method: o Observations: Gathering qualitative and quantitative data. o Formulation of hypotheses: A tentative interpretation or explanation for an observation. o Experimentation: A set of highly controlled procedures designed to test whether an idea about nature is valid. o Formulation of laws and theories A scientific law is a statement that summarizes all past observations and predicts future observations. Law of Conservation of Mass: “In a chemical reaction matter is neither created nor destroyed.” Significant Figures: o Any digit that is not zero is significant. o Zeroes between nonzero digits are significant. o Zeroes to the left of the first nonzero digit are not significant. o If a number is greater than 1, then all zeros to the right of the decimal point are significant. o If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant. o Addition or Subtraction: The answer cannot have more digits to the right of the decimal point than any of the original numbers. o Multiplication or Division: The number of significant figures in the result is set by the original number that has the smallest number of significant figures. Dalton’s atomic theory explained the laws as follows: o Each element is composed of tiny, indestructible particles called atoms. o All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements. o Atoms combine in simple, whole-number ratios to form compounds. o Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms change only the way that they are bound together with other atoms. Law of definite proportions: All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements. Law of multiple proportions: When two elements (call them A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers. q/m = -1.7588 x 10 C g for electron. Beta particles: negatively charged = electrons. Alpha particles: positively charged Ernest Rutherford showed that these are chemically part of helium atoms. The nuclear theory of the atom has three basic parts: o Most of the atom’s mass and all of its positive charge are contained in a small core called a nucleus. o Most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed. o There are as many negatively charged electrons outside the nucleus as there are positively charged particles (named protons) within the nucleus, so that the atom is electrically neutral. The mass of the proton is 1.67262 × 10 –27kg. The mass of the neutron is 1.67493 × 10 –27kg. The mass of the electron is 9.1 × 10 –31kg. The number of protons defines the element. The number of protons in an atom’s nucleus is its atomic number and is given the symbol Z. All atoms of a given element have the same number of protons; however, they do not necessarily have the same number of neutrons. Atoms with the same number of protons but a different number of neutrons are called isotopes. The sum of the number of neutrons and protons in an atom is its mass number and is represented by the symbol A. A = number of protons (p ) + number of neutrons (n) The relative amount of each different isotope in a naturally occurring sample of a given element is roughly constant. These percentages are called the natural abundance of the isotopes. + Positively charged ions are called cations. Metal elements, such as Na , form cations. Negatively charged ions are called anions. Nonmetal elements, such as F , – form anions. Atomic mass is sometimes called atomic weight or standard atomic weight. The atomic mass of each element is directly beneath the element’s symbol in the periodic table. The atomic mass of an element represents the average mass of the isotopes that compose that element. The masses of atoms and the percent abundances of isotopes of elements are measured using mass spectrometry—a technique that separates particles according to their mass. Worked Questions and Answers
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