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Home , Chemical compound, Chemical property

Basics

I. Intro A. Chemistry Def- a science that studies the composition and properties of . 1. matter- anything that takes up space and has .

B. Basic Terms: 1. : neutral particle having one nucleus; the smallest representative sample of an element. In other words it is the base building block, of an element. 2. Element: a substance in which all of the have the same atomic number. A substance that cannot be broken down by chemical reactions into anything that is both stable and simpler. Furthermore, all the atoms within an element have the same number of . 3. : a neutral particle composed of two or more atoms combined in a definite ratio of whole numbers. 4. Compound: a substance consisting of chemically combined atoms from two or more elements and present in a definite ratio.( mass is always 8 times that of ) 5. Physical property: a property that can be observed without changing the chemical makeup of a substance. (eg. Color) Is point one? 6. : chemicals, starting materials (reactants), interact with each other resulting in other substances, ending materials (products), with different properties. 7. Chemical Property: The ability of a substance, either by itself or with other substances, to undergo a change into new substances. 8. Extensive Property: a property that depends on sample size.(Volume) 9. Intensive Property: properties independent of size. ( Color, electrical conductivity, …) 10. Pure substance: a substance that is always the same, regardless of its source. 11. : a physical combination of elements or compounds that has no particular proportion by mass. a. Homogeneous -a mixture that has uniform properties throughout and only one phase. b. Heterogeneous mixture-a mixture that does not have uniform properties throughout and has more than one phase. 1. phase- a homogenous region within a sample or mixture. 12. Law of Conservation of Mass: The sum of all the mass in the universe is constant. 13. Law of Definite Proportions: In a given chemical compound, the elements are always combined in the same proportion by mass. You get the proportions by taking the elements that make up the compound and their individual contributions to the compound. for example, 18g H 20 is made of 2g of H and 16g of O, 2H’s:16O’s or 1 H : 8 O. You can then use this ratio to quantify unknown amounts of elements given one of the amounts or given an amount of a sample.

14. Dalton’s : a. Matter consists of tiny particles called atoms. b. Atoms are indestructible. In chemical reactions, the atoms rearrange but they themselves do not break apart. c. In any sample of a pure element, all the atoms are identical in mass and other properties. d. Atoms in different elements have different properties and mass. e. When atoms of different elements combine to form compounds, new and more complex particles form. However, in a given compound the constituent atoms are always present in the same fixed numerical ratios. *Note- atoms rearrange but are not destroyed(indestructible) which restates conservation of mass.

15. Law of multiple proportions: Whenever two elements form more than one compound, the different masses of one elelement that combine with the same mass of the other are in a ratio of small numbers. In other words, if the two compounds possible have 1 element that have the same mass ratio, X, and the other is different, N.

Eg. XN 3 vs XN 4 element X has the same proportion of mass and number; whereas, N has a ratio of 3 : 4.

16. Protons: A subatomic particle with a charge of +1 and a mass of 1.67 X 10 -24 g and is found in the nucleus. 17. Neutrons: a subatomic particle with neutral charge and a mass of 1.67 X 10 -24 g and that is found in all nuclei except for those of the hydrogen – 1 . 18. : a subatomic particle with a charge of -1 and a mass of 9.1 X 10 -28 g. It is found outside the atomic nucleus orbiting it. The is what moves when an electric current flows. 19. Nucleus: the hard dense core of an atom that holds the atom’s protons and neutrons.

B. : A table in which symbols for the elements are displayed in order of increasing atomic number and arranged so that elements with similar properties lie in the same column.

1. Atomic Mass (weight): the average mass of the atoms of the of a given element as they occur naturally. 2. Isotopes: Atoms of the same element with different atomic masses. Atoms of the same element with different numbers of neutrons in their nuclei. 3. Atomic Mass Units: 1.6606 X 10 -24 g; one twelfth the mass of one atom of -12. symbol- amu. 4. Atomic Number(Z): the number of protons in a nucleus. Atomic number(number of protons) X 5. Mass Number: The numerical sum or protons and neutrons in an atom of a given isotope. Mass number( protons + neutrons) X 6. Groups: vertical columns of elements in the periodic table. Usually share in properties and number. 7. Periods: horizontal row of elements on the periodic table. 8. Alkali : Group IA in the periodic table(except hydrogen) that have similar properties and share a valence number of one. 9. Alkali earth metals: Group IIA in the periodic table that share similar properties and valence number 10. Noble : Group VIII A in the periodic table. Very unreactive except the heavier members which have a small degree of . 11. : Group VII A of the periodic table. Valence number 7. 12. Transition elements: elements that fall in the center of the periodic table. Mostly metals. 13. Inner transition elements: Bottom two rows outside the periodic table. 14. Lanthanide elements: elements 58-71. So named because they come after lanthanum Z = 57. 15. elements: elements 90-103. So named because they follow actinium Z = 89. 16. : elements that share metallic and nonmetallic properties. Eg. Silicon and Arsenic. 17. Malleability: the ability of a to be hammered or rolled into thin sheets. 18. Ductility: the ability of a metal to be stretched or drawn into a wire. 19. Diatomic : all free nonmetallic elements exist as molecules composed of two atoms each. Elements are Hydrogen, , Oxygen, Flourine, Chlorine, Bromine, and . 20. : compounds whose crystalscontain water molecules in fixed ratios. Written as crystal : water eg. CaSO 4 : 2 H 2O. 21. Molecular compounds: a combination of two nonmetallic compounds. 22. Ionic compounds: a combination of a metallic and nonmetallic elemnt. 23. Anion: a negatively charged . 24. Cation: a positively charged ion. 25. Quantitative: numerical observation that can be measured numerically on some sort of scale. 26. Qualitative: observations of change of physical properties such as color. 27. Accuracy: the calibration of the instrument used to measure. 28. Precision: the closeness of the repeated measurements of the same quantity.

C. Scientific Method- 1. Identify a problem- what is it that you are going to study. This entails background research on the topic and observation of the phenomena being studied. This is the foundation for the question/statement your will make about the phenomena that you are observing. 2. Formulate a hypothesis: based on what you observed, what do you propose is happening. This will be the question or statement that you are asking the experiment to prove or disprove. 3. Conduct an experiment : a set of procedures that you orchestrate to test your hypothesis. The set of procedures must produce observations that are reproducible. A good experimenter takes good data. a. observation- a statement that accurately describes something we see, hear, taste, feel, or smell. b. data- empirical facts gathered during the experiment while observing some physical, chemical, or biological system. * the observations we make should relate the factors of your experimental data. 4. Formulate a conclusion: a statement tying together the set of observations.

If the results and conclusion are reproducible by the scientific community, the generalizations that your experiments yield could become scientific law, and could result in mathematical equations and more.

• However, a law only can dictate what will happen and how the properties are related. They do not explain the why? A scientific theory must be developed to explain the why observed laws are occurring. The overall interplay between making the theory and testing it is the essence of the scientific method.

C. Significant Figures: 1. Zeros to the right of a decimal point are always significant. 2.500 all zeros sig 2. Zeros to the left of the first nonzero number are always considered to be NONsignificant. 0.0001 non of these are sig 3. Zeros at the end of a number without a decimal point are considered to be NONsignificant. 25,000 non sig 4. Zeros in scientific notation are sig. 2.50 X 10 4 has 3 sig figs. 5. Multiplication and division, the number of sig figs in the answer should not b e greater than the number of sig figs in the least precise measurement(smallest # of sig figs) (11.2 X 2.50)/0.62 should have only 2 sig figs. 6. Addition and subtraction the answer should have the same number of decimal places as the quantity with the fewest number of decimal places. 1.22 + 2.1 +2.354 should only have one decimal.