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Resources Chapter Presentation Visual Concepts Transparencies Standardized Test Prep
Chapter 2 Chemistry of Life Table of Contents Section 1 Composition of Matter Section 2 Energy Section 3 Water and Solutions
Section 1 Composition of Matter Chapter 2 Objectives • Definethe term matter. • Explainthe relationship between elements and atoms. • Draw and label a model of the structure of an atom. • Explain howcompounds affect an atom’s stability. • Contrast covalent and ionic bonds.
Section 1 Composition of Matter Chapter 2 Matter • Matteris anything that occupies space and has mass. • Massis the quantity of matter an object has.
In recent times, we have begun to study matter at the very high temperatures and pressures which typically occur on the Sun, or during re-entry from space. Under these conditions, the atoms themselves begin to break down; electrons are stripped from their orbit around the nucleus leaving a positively charged ion behind. The resulting mixture of neutral atoms, free electrons, and charged ions is called a plasma, the forth state of matter.
Section 1 Composition of Matter Chapter 2 Elements and Atoms • Elementsare made of a single kind of atom and cannot be broken down by chemical means into simpler substances. • About 100 million atoms side by side = 1 cm • About 25 different chemical elements are essential to life • 4 elements make up 96% of the human body by weight. Which ones are they?
Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, but there are other elements necessary for life . Trace elements are essential (<0.01% wet weight). • Flouride is in our water and iodine is in our salt. Iron is in our red blood cells and is found in the heme group of the hemoglobin molecule. Table 2.2
Goiters are caused by iodine deficiency • The thyroid gland requires .15mg I/day for normal function. Iodine is essential in the formation of thyroid hormone, which is composed of four molecules of iodine and one molecule of the amino acid tyrosine. Figure 2.2
Section 1 Composition of Matter Chapter 2 Elements and Atoms, continued • Atoms of the various elements are made up of protons, neutrons and electrons. • The Nucleus • Protons and neutrons make up the nucleus of the atom. • Protons have a positive charge • Neutrons are neutral _ N +
Section 1 Composition of Matter Chapter 2 Elements and Atoms, continued • Electrons • Electronsmove about the nucleus in orbitals and have a negative charge. • The number of electrons equals the number of protons; thus an atom is neutral. • An orbital is a three-dimensional region around a nucleus that indicates the probable location of an electron.
The atom is held together by attractions between the positively charged protons and negatively charged electrons • Atoms of each element are distinguished by a specific number of protons. The number of protons is equal to the number of electrons. • Neutrons are electrically neutral • The number of neutrons may vary • Variant forms of an element are called isotopes 6 Protons Nucleus 6 Neutrons 6 Electrons B. Carbon atom Figure 2.4B
Section 1 Composition of Matter Chapter 2 Elements and Atoms, continued • Isotopes • Atoms of the same element that have a different number of neutrons are calledisotopes.
The number of neutrons may vary • Variant forms of an element are called isotopes • Some isotopes are radioactive • The atomic mass of Carbon is 12.01. This is the average mass of the various isotopes of carbon found in nature. C-14 is radioactive. % in nature 98.89 C12 1.11 C13 Trace C14 Table 2.4
Radioactive isotopes can help or harm us • Radioactive isotopes can be useful tracers for studying biological processes. Living cells do not know the difference between isotopes. • Every organ in our bodies acts differently from a chemical point of view. Doctors and chemists have identified a number of chemicals which are absorbed by specific organs. The thyroid, for example, takes up iodine, the brain consumes quantities of glucose, and so on. With this knowledge, radiopharmacists are able to attach various radioisotopes to biologically active substances. Once a radioactive form of one of these substances enters the body, it is incorporated into the normal biological processes and excreted in the usual ways. • http://www.uic.com.au/nip26.htm
Radioactive isotopes can help or harm us • PET scanners use radioactive isotopes to create anatomical images • http://en.wikipedia.org/wiki/Positron_emission_tomography • A substance that emits positrons is injected into the patient. The positrons collide with electrons in tissues that are metabolically active. The energy released by these collisions is registered as “hot spots”. Figure 2.5A Figure 2.5B
Isotopes Used in Medicine • Molybdenum-99 Used as the “parent” to produce technetium-99m the most widely used isotope in nuclear medicine. • Technetium-99m Most widely used to image the skeleton and heart muscle. Technetium-99m decays by a process called "isomeric"; which emits gamma rays and low energy electrons. Since there is no high energy beta emission the radiation dose to the patient is low. • Chromium-51 Used to label rbc’s and gastro intestinal protein loss • Cobalt-60 Used for radiotherapy • Dysprosium-165 Used in the synovectomy treatment of arthritis • Ytterbium-169 Cerebrospinal studies of the brain • Iodine-125 Used in prostate and brain cancer therapy. Used to diagnose deep vein thrombosis. Used to assay for hormones present in minute quantities • Iodine 131 Treating thyroid cancer and imaging the thyroid. Used in diagnosis of liver function, kidney blood flow and urinary tract obstruction. A strong gamma emitter, but is used for beta therapy.
Carbon Dating • Research Carbon Dating. • Discover the theory, the • advantages and the drawbacks of the technique. • Complete a 2 page essay on the • use of Carbon Dating Beta decay is when an electron and positron are emitted
Electron arrangement determines the chemical properties of an atom • Electrons are arranged in shells • The outermost shell determines the chemical properties of an atom • In most atoms, a full outer shell holds eight electrons. A happy atom!!!!!!
Atoms whose shells are not full tend to interact with other atoms and gain, lose, or share electrons. Hum….. Outermost electron shell (can hold 8 electrons) Electron First electron shell (can hold 2 electrons) HYDROGEN (H) Atomic number = 1 CARBON (C) Atomic number = 6 NITROGEN (N) Atomic number = 7 OXYGEN (O) Atomic number = 8 Figure 2.6
Section 1 Composition of Matter Chapter 2 Compounds • Compoundsconsist of atoms of two or more elements that are joined by chemical bonds in a fixed proportion.
Sodium and chloride ions bond to form sodium chloride, common table salt Na+ Cl– Figure 2.7B
Section 1 Composition of Matter Chapter 2 Compounds, continued • Ionic Bonds • An ionic bond is formed when one atom gives up an electron to another. The positive ion is then attracted to a negative ion to form the ionic bond.
Ionic bonds are attractions between ions of opposite charge • When atoms gain or lose electrons, charged atoms called ions are created • An electrical attraction between ions with opposite charges results in an ionic bond – + Na Cl Na Cl Na Sodium atom Cl Chlorine atom Na+ Sodium ion Cl– Chloride ion Figure 2.7A Sodium chloride (NaCl)
Section 1 Composition of Matter Chapter 2 Ionic Bonding
Section 1 Composition of Matter Chapter 2 Compounds, continued • Covalent Bonds • A covalent bond is formed when two atoms share electrons.
Covalent bonds, the sharing of electrons, join atoms into molecules • Some atoms share outer shell electrons with other atoms, forming covalent bonds • Atoms joined together by covalent bonds form molecules
Because of the nature of ionic and covalent bonds, the materials produced by those bonds tend to have quite different macroscopic properties. The atoms of covalent materials are bound tightly to each other in stable molecules, but those molecules are generally not very strongly attracted to other molecules in the material. On the other hand, the atoms (ions) in ionic materials show strong attractions to other ions in their vicinity. This generally leads to low melting points for covalent solids, and high melting points for ionic solids. For example, the molecule carbon tetrachloride is a non-polar covalent molecule, CCl4. It's melting point is -23°C. By contrast, the ionic solid NaCl has a melting point of 800°C. Furthermore, ionic bonds themselves tend to be weaker than covalent bonds, but this is a topic for a more advanced chemistry course as it is a generalization.
Section 2 Energy Chapter 2 Objectives • Describethe physical properties of each state of matter. • Describethe role of reactants and products in chemical reactions. • Explainthe relationship between enzymes and activation energy. • Explainhow oxidation and reduction reactions are linked.
Section 2 Energy Chapter 2 Energy and Matter • States of Matter • Addition of energy to a substance can cause its state to change from a solid to a liquid and from a liquid to a gas. • What is plasma?
Section 2 Energy Chapter 2 Energy and Chemical Reactions • Reactantsare substances that enter chemical reactions. • Products are substances produced by chemical reactions.
Section 2 Energy Chapter 2 Energy and Chemical Reactions
Section 2 Energy Chapter 2 Energy and Chemical Reactions, continued • Activation Energy • Enzymes lower the amount of activation energy necessary for a reaction to begin in living systems.
Section 2 Energy Chapter 2 Activation Energy and Chemical Reactions
Section 2 Energy Chapter 2 Energy and Chemical Reactions, continued • Oxidation Reduction Reactions • A chemical reaction in which electrons are exchanged between atoms is called an oxidation-reduction reaction.
Section 3 Water and Solutions Chapter 2 Objectives • Describethe structure of a water molecule. • Explainhow water’s polar nature affects its ability to dissolve substances. • Outline the relationship between hydrogen bonding and the different properties of water. • Identify the roles of solutes and solvents in solutions. • Differentiate between acids and bases.
Section 3 Water and Solutions Chapter 2 Polarity • Water is considered to be apolarmolecule due to anuneven distribution of charge. • The electrons in a water molecule are shared unevenly between hydrogen and oxygen.
Section 3 Water and Solutions Chapter 2 Polarity, continued • Solubility of Water • The polarity of water makes it effective at dissolving other polar substances such as sugars, ionic compounds, and some proteins.
Section 3 Water and Solutions Chapter 2 Hydrogen Bonding • A hydrogen bondis the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge.
Section 3 Water and Solutions Chapter 2 Hydrogen Bonding, continued • Cohesion and Adhesion • Cohesion is an attractive force that holds molecules of a single substance together, such as water molecules. • Adhesionis the attractive force between two particles of different substances, such as water molecules and glass molecules.
Section 3 Water and Solutions Chapter 2 Comparing Cohesion and Adhesion
Section 3 Water and Solutions Chapter 2 Hydrogen Bonding, continued • Temperature Moderation • Water has the ability to absorb a relatively large amount of energy as heat and the ability to cool surfaces through evaporation.
Section 3 Water and Solutions Chapter 2 Hydrogen Bonding, continued • Density of Ice • Solid water is less dense than liquid water due to the shape of the water molecule and hydrogen bonding.
Section 3 Water and Solutions Chapter 2 Solutions • A solutionconsistsof a solute dissolved in a solvent.
Section 3 Water and Solutions Chapter 2 Acids and Bases • Ionization of Water • Water ionizes intohydronium ions(H3O+) and hydroxide ions (OH–).
Section 3 Water and Solutions Chapter 2 Acids and Bases, continued • Acids • Acidic solutionscontain more hydronium ions than hydroxide ions.
Section 3 Water and Solutions Chapter 2 Acids and Bases, continued • Bases • Basic solutionscontain more hydroxide ions than hydronium ions.
Section 3 Water and Solutions Chapter 2 Bases
Section 3 Water and Solutions Chapter 2 Acids and Bases, continued • pH • Scientists have developed a scale for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution. This scale is called the pH scale, and it ranges from 0 to 14.