Chemistry 101 1st Edition Exam 1 Study Guide Lectures Chapter 1 lecture 1 Classifying Matter Introduction to Chemistry and matter Define key characteristics of solids liquids and gases Know how to classify matter into elements compounds heterogeneous mixtures and homogeneous mixtures Matter anything that occupies space or has mass Three types of matter solid liquid gas Solid doesn t flow Constant volume and shape Molecules are close together Liquid flows Constant volume takes shape of container Gas can have a lot of space between molecules No constant volume or shape Spreads to fill container entirely Classifying Matter by Compostion Matter can be a pure substance or a mixture Pure Substance made of 1 type of atom or molecule Element CANNOT be broken down into simpler substance One kind of atom o Can also be molecules like O2 Compounds Molecules composed of 2 or more atoms Same compounds throughout substance o Most natural substances are compounds o E g H2O Mixture Two or more types of compounds Homogenous mixture uniform composition throughout o Every piece of sample has identical characteristics o E g milk Heterogeneous mixture do NOT have uniform mixture throughout o Regions within sample can have different characteristics E g chicken noodle soup Chapter 1 Lecture2 Scientific Approach to Knowledge Define what constitutes a good scientific hypothesis scientific theory and scientific law Scientists try to understand the universe through empirical knowledge gained through observation and experiment Types of observation Qualitative observations that are descriptive of characteristics or behavior Quantitative Some observations compare to a standard numerical scale What is a Hypothesis A tentative interpretation or explanation for an observation After experiment hypothesis is either vaild or invalid NEVER proven What is an experiment A set of highly controlled procedures designed to test whether an idea about nature is valid Scientific Theory general explanation for why things in nature are the way they are and behave the way they do supported heavily e g theory of gravity Scientific Law a statement that summarized all past observations and predicts future observations e g Law of conservation of mass in a chemical reaction matter is neither created nor KNOW THIS TABLE Describes what happens Explains why things happen Applies to single or small number of events Observation Hypothesis Applies to all events Law Theory destroyed Chapter 1 Lecture3 Atoms and Elements Law of definite proportions law of multiple proportions Dalton s atomic theory cathode rays and what they tell us Mullikan s experiment and what we learn from it Rutherford s gold foil experiment and what we learn from it the electron The Atom All matter is made of atoms and they cannot be created or destroyed in a chemical reaction Structure of the atom o Proton lives in the nucleus Positive 1 amu o Neutron lives in the nucleus No charge 1 amu o Electron orbits the nucleus Negative charge Negligible mass The Elements Each element has a specific amount of protons Isotopes Ions o THIS is what defines it Number of protons is called the atomic nucleus and is represented by symbol Z All atoms of a given element have the same number of protons Number of neutron can vary these are called isotopes Atoms that have lost or gained electrons Properties of ions are DIFFERENT from parent atom Experiments History to Know Law of Conservation of Mass In a chemical reaction matter is neither created or destroyed Mass of what you end up with MUST equal what you started with Discovered by Antoine Laviosier Law of Definite Proportions All samples of a pure substance always have same proportion of constituent elements E g 40 0 g of Carbon Dioxide is made up of 12 0 grams of carbon How much oxygen is present What is the ratio of oxygen carbon o Answer 28 0 grams of oxygen Ratio is 7 3 John Dalton and the Atomic Theory Elements are made up of atoms All atoms of a given element are identical o Not entirely true due to ions and isotopes Atoms cannot be created or destroyed Compounds are made of atoms combined in whole number ratios During a chemical reaction atoms are separated and combined Charges A quick refresher Positive and negative attract each other Negative and negative repel Positive and positive repel J J Thomson and the Cathode Ray Tube discovered the electron Metal electrodes on each side one and one When connected to high voltage power supply glowing area is seen emanating from cathode o Beam is deflected and flows from to o This happened every time o Different materials tested every material tested contained these same particles Watch for further explanation https www youtube com watch v GzMh4q 2HjM Thomson s Conclusion If the particle has the same amount of charge as a hydrogen ion then it must have a mass almost 2000x smaller than hydrogen atoms Millikan s Oil Drop Experiment Small drops of oil suspended in a chamber and when they fell they were negatively charged through ion radiation Millikan applied an electric field in the chamber to stop drops from falling Millikan found that the charge on each drop was multiple of 1 6x10 19 C o This is the charge of an electron Watch for further explanation https www youtube com watch v XMfYHag7Liw Electrons Electrons are tiny negative charged particle All atoms are made from electrons Cathode rays are streams of electrons Plum Pudding Model J J Thomson s pudding model of the atom If the atoms was like this then positive particles should go straight through o Not true proven by rutherford s gold foil experiment Rutherford s Gold Foil Experiment Alpha positively charged particles were shot through a sheet of gold foil If the plum pudding model was correct the particles should go straight through However a few alpha particles were deflected at small AND large angles Rutherford s Conclusions Most alpha particles travel straight through therefore matter is mostly empty space A few alpha particles bounce back therefore there must be something small and dense and positively charged within matter The nucleus or center of the atom is composed of protons that have same magnitude of charge as electrons but opposite sign The Neutron All atomic nuclei have protons and most have neutrons No charge and weight of 1 amu Chapter 1 Lecture4 Atomic Mass and Mass Spectrometry Calculated the average atomic mass of an element interpret simple mass spectra relate mass spectra to average atomic mass of an element