The structure of_matter
- 1. The Structure of Matter Chapter 2: Chemical Basis of Life
- 2. What is Matter? Matter is anything that has weight and takes up space. This includes the solids, liquids, and gases in our surroundings, as well as inside our bodies.
- 3. What is it Made of? All matter is composed of substances called Elements . At present, 111 elements are known, although naturally occurring matter on Earth includes only 92 of them. Although some of these elements exist in a pure form, they occur more frequently in mixtures of chemical combinations.
- 4. Elements We Need Living organisms require about 20 elements. Of these carbon, hydrogen, oxygen, phosphate, nitrogen, sulfur make up more than 98% (by weight) of the human body.
- 5. Elements Elements are composed of tiny particles called Atoms , which are the smallest complete units of elements. All the atoms of an element look nearly identical to one another, but different from atoms of another element. Atoms vary in size, weight, and the ways they interact with each other.
- 6. How are they different? Oxygen Carbon
- 7. Atomic Structure An atom consists of a central portion, called the Nucleus , and one or more Electrons that move around it. The nucleus contains one or more relatively large particles called Protons . The nucleus also usually contains one or more Neutrons , which are similar in size to protons.
- 8. More on Atomic Structure Electrons (extremely tiny) each carry a single, negative electrical charge Protons each carry a single, positive electrical charge. Neutrons are uncharged and are electrically neutral.
- 10. Chemistry Vocab. Review Atomic Number : the number of protons in the atoms of a particular element.
- 11. Chemistry Vocab. Review Atomic Weight : Approximately the number of protons plus the number of neutrons in each of an element’s atoms.
- 12. Let’s Bond! When atoms combine with other atoms, they either gain electrons, lose electrons, or share electrons. The electrons of an atom occupy one or more areas of space called Shells around the nucleus. The outermost shell of an atom determines its chemical behavior.
- 13. Stability vs. Instability Atoms whose outermost electron shells are filled, have stable structures and are chemically inactive ( inert )- Example : Helium Atoms whose outermost electron shells are incompletely filled, tend to gain, lose, or share electrons in ways that empty or fill their outer shells. In this way, they achieve stable structures.
- 14. Types of Bonds 1. Ionic Bonds 2. Covalent Bonds 3. Hydrogen Bonds
- 15. Ionic Bonding An Ionic Bond is a chemical bond formed between two (oppositely charged) ions by the transferring of electrons . Example : Sodium ions (Na + ) and chloride ions (Cl - ) uniting in this manner form the compound sodium chloride (NaCl), or table salt.
- 17. Covalent Bonding Nature likes filled levels for stability, why not share? A Covalent Bond is a chemical bond formed by electron sharing between atoms.
- 19. Hydrogen Bonding A Hydrogen Bond is a weak electrical attraction between a hydrogen atom (covalently bound to a nitrogen or oxygen atom) and another nitrogen or oxygen atom nearby .
- 20. Hydrogen Bonding Hydrogen bonds only occur with molecules that are polar . Water is polar because the oxygen atom & hydrogen atoms share electrons unevenly.
- 21. Molecules & Compounds When two or more atoms bond, they form a new kind of particle called a Molecule . If atoms of the same element combine, they produce molecules of that element. Example: H 2 , O 2 When atoms of different elements combine, they form molecules called Compounds . A molecule of a compound always contains definite kinds and numbers of atoms. Example: CO 6 , H 2 O, C 6 H 12 O 6
- 22. Chemical Reactions Chemical rxns form or break bonds between atoms, ions, or molecules, generating new chemical combinations. 1. Synthesis Reactions 2. Decomposition Reactions 3. Exchange Reactions 4. Reversible Reactions
- 23. Synthesis Reactions When two or more atoms (reactants) bond to form a more complex structure (product). A + B AB Requires an input of energy (endergonic) Important in the growth of body parts and the repair of worn or damaged tissues.
- 24. Decomposition Reactions When the bonds within a reactant molecule break so that simpler molecules, atoms, or ions form. AB A + B Decomposition occurs when foods are digested and energy is released (exergonic)
- 25. Exchange Reaction Parts of two different types of molecules trade positions. AB + CD AD + CB An example is when an acid reacts with a base, producing water and a salt. HCl + NaOH --> NaCl + H 2 O
- 26. Reversible Reactions Most chemical reactions are reversible. The product (or products) of the reaction can change back to the reactant (or reactants) that originally underwent the reaction. A + B AB
- 27. Understanding Electrolytes Some compounds release ions when they dissolve in water or react with water molecules. Example : NaCl releases sodium ions (Na + ) and chloride ions (Cl - ) when it dissolves: NaCl Na + + Cl -
- 28. Understanding Electrolytes NaCl Na + + Cl - Since the resulting solution contains electrically charged particles (ions), it will conduct an electric current. Substances that release ions in water are called Electrolytes .
- 29. Acids & Bases Electrolytes that release hydrogen ions in water (H + ) are called Acids . Example : In water, the compound hydrochloric acid (HCl) releases hydrogen ions (H + ) and chloride ions (Cl - ) Electrolytes that release hydroxide ions in water (OH - ) are called Bases . Example : The compound sodium hydroxide (NaOH) releases hydroxide ions (OH - ) when placed in water.
- 30. pH Scale A value called pH measures hydrogen ion concentration. The pH scale ranges from 0 to 14. A solution that contains equal numbers of hydrogen and hydroxide ions is said to be neutral, and has a pH of 7. A solution that contains more hydrogen than hydroxide ions has a pH less than 7 A solution that contains less hydrogen than hydroxide ions has a pH more than 7 Each whole number on the scale represents a tenfold difference in hydrogen ion concentration.
- 31. Human Implications The pH of human blood is about 7.4 (range is from 7.35 to 7.45) If this pH value drops below 7.35, the person is said to have Acidosis If this pH value rises above 7.45, the person is said to have Alkalosis Without medical intervention, a person usually cannot survive if blood pH drops to 6.9 or rises to 7.8 for more than a few hours.