Chemistry
All Materials Cmassengale

Composition of Matter

  Everything in the universe is made of matter

  Matter takes up space & has mass

  Mass is a measure of the amount of matter in the substance

  Mass & weight are NOT the same

  Weight is a measure of the pull of gravity on an object

Question: Is the mass of an object the same on the moon as it is on the Earth? Is its weight the same? (Hint: Gravitational pull on the moon is 1/6 of that on the Earth.)

  Matter exists in 4 states solid, liquid, gas, & plasma

  Solids have both a definite volume & definite shape (rock)

  Liquids have a definite volume but no definite shape; they can be    poured (water)

  Gases do not have a definite volume or definite shape, but they take the  volume & shape of their container

  Plasmas have no definite volume, no definite shape, and only exist at extremely high temperatures such as the sun

  Chemical Changes in matter are essential to all life processes

  Biologists study chemistry because all living things are made of the same kinds of matter that make up nonliving things

Elements

     Elements are pure substances which cannot be chemically broken down into simpler kinds of matter

     More than 100 elements have been identified, but only about 30 are important in living things

     All of the Elements are arranged on a chart known as the Periodic Table

     Periodic charts tell the atomic number, atomic mass, & chemical symbol for every element  

     Four elements, Carbon C, Hydrogen H, Oxygen O, and Nitrogen N make up almost 90% of the mass of living things

     Every element has a different chemical symbol composed of one to two letters

     Chemical symbols usually come from the first letter or letters of an element like C for Carbon and Cl for Chlorine

     Some chemical symbols come form their Latin or Greek name such as  Na for Sodium (natrium) or K for Potassium (Kalium)

      Elements in the same horizontal period on the periodic table have the same number of energy levels (e.g. H & He in period 1 have only a K energy level)

[Periodic Table]
All Period 2 elements have 2 energy levels
 (K & L)

      Elements in the same vertical Family on the periodic table have the same number of electrons in their outermost energy level & react similar (e.g. Family IV, the Carbon family all have 4 electrons in their outermost energy level)

Atoms

     Atoms are the simplest part of an element that keeps all of the elements properties

     Atoms are too small to be seen so scientists have developed models that show their structure & properties

     Atoms consist of 3 kinds of subatomic particles protons & neutrons in the center or nucleus, and electrons spinning in energy levels around the center

     The nucleus is the center of an atom where most of the mass is concentrated

     Protons are positively charged ( p+ ),  have a mass of 1 amu (atomic mass unit) , are found in the nucleus, and determine the atomic number of the element

Example:  Carbon has 6 protons so its atomic number is 6

     Neutrons are neutral or have no electrical charge (n), have a mass of 1 amu, are found in the nucleus, and when added to the number of protons, determine the atomic mass of the element

Example:  Sodium has 11 protons and 12 neutrons so its atomic mass is 11+12=23 amu

     Electrons (e-) are negatively charged, high energy particles with little mass that spin around the nucleus in energy levels

     Seven energy levels (K, L, M, N, O, P, & Q) exist around the nucleus and each holds a certain number of electrons

     The K energy level is closest to the nucleus & only holds 2 electrons, while the  L Q energy levels can hold 8 electrons  

     Electrons in outer energy level are traveling faster & contain more energy than electrons in inner levels  

     The number of protons (positive charges) and electrons (negative charges in an atom are equal so the net electrical charge on a atom is zero making it electrically neutral

     Stable or non-reactive atoms have an outer energy level that is filled with electrons  

Compounds

     Most elements do not exist by themselves; Most elements combine with other elements

      Compounds are made of atoms of two or more elements chemically combined

      Chemical Formulas represent a compound & show the kind & number of atoms of each element  (e.g. H2O has 2 hydrogen & 1 oxygen)

      Compounds have different physical & chemical properties than the atoms that compose them  (e.g. hydrogen & oxygen are gases but H2O is a liquid)

      The number & arrangement of electrons in an atom determines if it will combine to form compounds

      Chemical reactions occur whenever unstable atoms (outer energy level not filled) combine to form more stable compounds

      Chemical bonds form between atoms during chemical reactions

Types of Chemical Bonds

     Covalent bonds form between atoms whenever they share 1 or more pairs of electrons (e.g. H2O)  

     Molecules form from covalent bonding & are the simplest part of a compound (e.g. NaCl, H2O, O2)  

     Ionic bonding occurs between a positively & negatively charged atom or ion  

     Positively charged ions have more electrons (-) than protons (+); negatively charged ions have more protons than electrons

     Table salt (NaCl) forms when the 1 outer electron of Na is transferred to the outer energy level of chlorine that has 7 electrons (e-)  

     Sodium (Na) with 1 less e- becomes positively charged, while Chlorine (Cl) with 1 more e- becomes negatively charged; the + and charges attract & form the ionic bond holding NaCl together

     Other types of chemical bonding include hydrogen bonding

Energy

     Energy is the ability to do work

     Energy occurs in several forms & may be converted from one form to another

     Sunlight is the ultimate energy for all life on earth

     Forms of energy include chemical, electrical, mechanical, thermal, light, & sound

     Free energy is the energy available for work (e.g. cells have energy to carry out cell processes)

     Cells convert the chemical energy stored in food into other types of energy such as thermal & mechanical

     Energy is used to change matter form one state into another (e.g. liquid into a gas)

Chemical Reactions

     Living things undergo thousands of chemical reactions

     Chemical equations represent chemical reactions

     CO2 + H20-----goes to-----H2CO3  (carbonic acid) is a sample Chemical Reaction in living things

     Reactants are on the left side of the equation, while products are on the right side  

Activation energy is required to start many reactions

     Chemical bonds are broken, atoms rearranged, and new bonds form in chemical reaction

     Plants use sunlight to produce sugars such as C6H12O6 glucose; the chemical energy from the sun is stored in the chemical bonds of glucose

      Organisms eat plants, break down the sugars, and release energy along with CO2 & H2O

      Exergonic reactions involve a net release of energy; while endergonic reactions involve a net absorption of energy

      Energy must be added to the reactants for most chemical reactions to occur; called activation energy

      Enzymes are chemical substances in living things that act as catalysts & reduce the amount of activation energy needed

      Organisms contain thousands of different enzymes

      Most enzymes end with ase (e.g. lipase is the enzyme that acts on lipids)

 Reduction-Oxidation (Redox) reactions

     Reactions in which e- are transferred between atoms is a redox or reduction-oxidation reaction (e.g. formation of table salt NaCl)

     In oxidation reactions, a reactant loses 1 or more e- & becomes positively (+) charged (e.g. Sodium atom becomes a Na+ ion)

     In a reduction reaction, a reactant gains 1 or more e- and becomes negatively (-) charged (e.g. Chlorine atom becomes a Cl- ion)

     REDOX reactions always occur together; the electron(s) from the oxidation reaction are then accepted by another substance in the reduction reaction

Solutions

     A large percentage of the mass of organisms is water & many of the chemical reactions of life occur in water

     A solution  is a uniform mixture of one substance in anther

     Solutions may be mixtures of solids, liquids, or gases

     The solute is the substance uniformly dissolved in the solution & may be ions, molecules, or atoms

     The solvent is the substance in which the solute is dissolved

     Water is known as the universal solvent 

     Dissolving one substance in another does not alter their chemical properties  

     The concentration of a solution is a measure of the amount of solute dissolved in a given volume of solvent

     Increasing the amount of solute increases the solutions concentration

     Aqueous solutions are solutions in which water is the solvent; these are important in living things (e.g. blood, cytoplasm of cell...)

Acids and Bases

     The degree of acidity or alkalinity (basic) is important in organisms

     The force of attraction between molecules is so strong that the oxygen atom of one molecule can actually remove the hydrogen from other water molecules; called Dissociation

      H20-----GOES TO----- H+  +  OH-

     OH- called hydroxide ion; H+ called hydrogen ion

     Free H+ ion can react with another water molecule to form H3O+  (hydronium ion)

     Acidity or alkalinity is a measure of the relative amount of H+ and OH- ions dissolved in a solution

     Neutral solutions have an equal number of H+ and OH- ions

     Acids have more H3O+ ions than OH- ions; taste sour; and can be corrosive

     Bases contain more OH- ions than H3O+ ions; taste bitter; & feel slippery  

Examples of Common Acids

  • citric acid (from certain fruits and veggies, notably citrus fruits)
  • ascorbic acid (vitamin C, as from certain fruits)
  • vinegar (5% acetic acid)
  • carbonic acid (for carbonation of soft drinks)
  • lactic acid (in buttermilk)

Examples of Common Bases

  • detergents

  • soap

  • lye (NaOH)

  • household ammonia 

PH Scale

     Compares the relative concentration of H3O+ ions and OH- ions

     Scale ranges from 0 to 14; 0-3 is very acidic; 7 is neutral; 11-14 is very basic or alkaline

 

    Litmus paper, phenolphthalein, pH paper, & other indicators that change color can be used to measure pH

 

Buffers

     Control of pH is important to organisms

     Enzymes function only within a narrow pH range; usually neutral

     Buffers neutral acids or bases in organisms to help control pH

Chemistry Study Guide

Chemistry On-line

 

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