# Chem MT 1-6 Cheat Sheet by rubycitalan

### The Scientific Method

 Chem­istry is the science that deals with the materials of the universe and the changes that these materials undergo. Steps: 1. State the problem and collect data (make observ­ations) 2. Formulate hypoth­eses. A hypothesis is a possible explin­ation for the observ­ation. 3. Preform Experi­ments. Gather new inform­ation that allows us to decide whether the hypothesis is supported by the new inform­ation we have learned

### Measur­ements and Calcul­ations

 Scientific notation expresses a number as a product of a number between 1 and 10 and the approp­riate power of 10. Ex. (100= 1.0×102 , 0.010=­1.0­×10­-2) If the decimal is moved to the left, the power of 10 is positive ; if the decimal is moved to the right, the power of 10 is negat­ive.

### Signif­icant Figures

 The numbers recorded in a measur­ement are called sign­ificant figures. 1. Nonzero integers always count as signif­icant figures. Ex. (4567 has four nonzero integers that count as signif­icant figures.) 2. Zeros. a. leading zeros never count as signif­icant figures. Leading zeros are all zeros that precede nonzero integers. b. captive zeros always count as signif­icant figures. Captive zeros are zeros that fall in between two nonzero digits. c. trailing zeros are sometimes signif­icant figures. Trailing zeros are zeros right at the end of a number. They are only signif­icant if the number is written with a decimal. (Ex. The number 100 only has one SF 1 ; but the number 100. has three SF. 3. Exact Numbers never limit the number of signif­icant figures in a calcul­ation. Sign­ificant figures also apply to scientific notati­on.

### TC Equations

 Temper­ature in Kelvins = Temper­ature in Celsius + 273 Temper­ature in Celsius = Temper­ature in Kelvin - 273 Temper­ature in Fahrenheit = 1.80( Temper­ature in Celsius) +32 Temper­ature in Celsius = Temper­ature in Fahrenheit - 32 / 1.80

### Elements and Compounds

 An elem­ent is a substance that cannot be broken down into other substances by chemical means. When elements combine, they form comp­oun­ds, which are substances that can be broken down into elements by chemical means.

### Pure Substances and Mixtures

 A pure substance is either an element or compound. A mixture can be defines as something that has variable compos­ition. Mixtures can be classified as either homoge­neous or hetero­gen­eous. A homog­eneous mixture is the same throug­hout. This type of mixture is also called a solution. A heter­oge­neous mixture contains regions that have different properties from those of other regions. These mixtures can be separated through dist­ill­ation and filt­rat­ion.

### Dalton's Atomic Theory

 1. Elements are made of tiny particles called atoms. 2. All atoms of a given element are identical. 3. The atoms of a given element are different from those of any other element. 3. 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. 4. Atoms are indivi­sible in the chemical process. Atoms are not created nor destroyed in chemical reactions. A chemical reaction simply changes the way the atoms are grouped together.

### Ions

 An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons. A cation is a positively charged ion; an ion that has lost electrons. An anion is a negatively charged; an atom that has gained electrons. Alkali Metals are the most reactive metals that can form cations easily by only needing to lose one valence electron. Halo­gens are the most reactive nonmetals that can form anions easily by only needing to gain one valence electron. Noble Gasses have 8 valence electrons so they are already stable. An ionic bond is a chemical bond resulting from the attraction between oppositely charged ions. A chemical compound must have a net charge of 0 (zero)

### Common Simple Cations and Anions

 Cation Name Anion Name H+ hydrogen H- hydride Li+ lithium F- fluoride Na+ sodium Cl- chloride K+ potassium Br- bromide Cs+ cesium I- iodide Be2+ beryllium O2- oxide Mg2+ magnesium S2- sulfide Ca2+ calcium Ba2+ barium Al3+ aluminum Ag+ silver Zn2+ zinc

### Common Type II Cations

 Ion Systematic Name Older Name Fe3+ iron(III) ferric Fe2+ iron(II) ferrous Cu2+ copper(II) cupric Cu+ copper(I) cuprous Co3+ cobalt­(III) cobaltic Co2+ cobalt(II) cobaltous Sn4+ tin(IV) stannic Sn2+ tin(II) stannous Pb4+ lead(IV) plumbic Pb2+ lead(II) plumbous Hg2+ mercur­y(II) mercuric Hg22+ mercury(I) mercurous
Mercury(I) ions always occur bound together in pairs to form Hg22+.

### Rules for Naming Acids

 If the anion does not contain oxygen, the acid is named with the prefix hydro- and the suffix -ic attatched to the rootname of the element. Ex. HCl= hydro­-c­hlo­r-ic acid 2. When anions contain oxygen, the acid name is formed from the root name of the central element of the anion or the anion name with the suffix of -ic or -ous. When the anion name ends in -ite, the suffix -ic is used. (Ex. H2SO4 = SO42-­(s­ulfate) = Sulfric Acid) When the anion name ends in -ite, the suffix -ous is used in the acid name. (Ex. H2SO3 = SO32- (sulfite) = Sulfurous acid)

### Chemical Equations

 We represent a chemical reaction by writing a chemical equation in which the chemical reactions (the reac­tan­ts) are shown to the left of an arrow and the chemicals are formed by the reaction (the prod­ucts) are shown to the right of the arrow. In the process of balancing equations is that atoms are conserved in a chemical reaction. The identities (formulas) of the compounds must never be changed in balancing a chemical equation.

### Balancing Equations

 Step 1 Read the descri­­ption of the chemical reaction. Step 2 Write the unbalanced equation that summarizes the inform­ation from step 1. Step 3 Balancing the equation by inspec­tion, starting with the most compli­cated molecule. Proceed element by element to determine what coeffi­cients are necessary so that the same number of each type of atom appears on both the reactant and the product side. Step 4 Check to that the coeffi­cients used, give the same number of each type of atom on both sides of the arrow. Also check to see that the coeffi­cients used are the smallest integers that give the balanced equations. This can be cone by determ­ining whether all coeffi­cients can be divided by the same integer to give a set of smaller integer coeffi­cients.

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