Unit 4: General Chemistry Matter and its properties

OBJ: Distinguish among atoms, elements, compounds, and molecules Matter OBJ: Distinguish among atoms, elements, compounds, and molecules

The Atom Basic unit of matter Made up of protons, neutrons, electrons

Atom: Subatomic particles Nucleus: protons (+) and neutrons (0) bind together at the center of the atom Electrons: negatively charged particle; constantly moving around the nucleus

Elements Pure substance Consists of one type of atom

Atomic Number = Proton #, electron # Atomic Mass = protons + neutrons

Main Elements in Living Things Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N) We also need: phosphorus and sulfer

Isotopes When an element has different number of neutrons Example: Carbon normally has 6; a carbon isotope would have 8 neutrons Isotopes have similar chemical properties because they have the same # of electrons

Radioactive Isotopes Some isotopes are unstable – their nuclei break down over a period of time Radioactive dating Can be used to determine ages of rocks and fossils Radiation from certain isotopes have help treat cancer

Compounds and Molecules Chemical combination of two or more elements Example: H2O, NaCl Elements that make up a compound can be very different from the actual compound (ie: oxygen is a gas at room temperature) Molecule= smallest unit of compounds

Practice using Periodic Table

Homework Pick 5 elements from the Periodic Table and identify the following: Name Atomic Number Atomic Mass Number of protons, neutrons, electrons

Electrons and Bonding OBJ: Describe the structure of an atom and the role of electrons in bonding

Electrons Bond formation involves the electrons that surround each atomic nucleus Valence electrons = electrons available to form bonds

Chemical Bonds Ionic Bonds Covalent Bonds When one or more electrons are transferred from one atom to another When electrons are shared between atoms Form Molecules

Chemical Bonds Ionic Bonds Covalent Bonds When one or more electrons are transferred from one atom to another When electrons are shared between atoms Form Molecules

Chemical Bonds Ionic Bonds Covalent Bonds When one or more electrons are transferred from one atom to another When electrons are shared between atoms Form Molecules

Chemical Equations http://youtu.be/dExpJAECSL8

Homework: Cayan Biology Flexbook Chemical Bonding Chapter Practice Questions 1-6

Water OBJ: DESCRIBE THE PROPERTIES OF WATER THAT MAKE IT A UNIQUE SUBSTANCE NECESSARY FOR LIFE.

The Water Molecule Oxygen end of molecule has a slightly negative charge Hydrogen end of molecule has a slightly positive charge Polar molecule: uneven distribution of electrons between the oxygen and hydrogen atoms

Poles of the Water Molecule

Hydrogen Bonds Not very strong Between two water molecules Water molecules can have multiple hydrogen bonds

Cohesion Attraction between molecules of the same substance Water is cohesive due to hydrogen bonding Responsible for surface tension

Adhesion Attraction between molecules of different substances Example: water molecules and glass molecules cause water to rise around the graduated cylinders

Properties of Water Polarity Cohesion Adhesion Surface tension Hydrophobic Hydrophilic

OBJ: Define pH and test the pH of various substances pH, Acids, Bases OBJ: Define pH and test the pH of various substances

The pH Scale Indicates the concentrations of H+ ions in a solution Ranges from 0-14 7 Neutral 14 very basic 0 very acidic

Acids Any compound that forms H+ ions in a solution Low numbers on the pH scale Examples: rain, tomato juice, lemon juice, stomach acid

Bases Compound that produces hydroxide ions High numbers on the pH scale Examples: Milk, Sea water, Soap, Bleach

Humans and pH Human fluids must generally be kept at 6.5-7.5 Controlling pH is important for maintaining homeostasis Medical Example: Heartburn