Introduction to Chemical Principles Chapters 1, 2 and 3
The Scientific Method The Scientific Method • Science is a framework for gaining and organizing knowledge. • The process that lies at the center of scientific inquiry is called the scientific method. http://askabiologist.asu.edu/explore/using-scientific-method-solve-mysteries
http://www.sciencebuddies.org/ science-fair-projects/project_ scientific_method.shtml
The Scientific Method Making observations. Observations may be qualitative or quantitative. • Qualitative observations do not involve numbers. • the sky is blue; water is a liquid • Quantitative observations involve both numbers and units. • also called a measurement • water boils at 100°C; a certain chemistry book weighs 2 kg
The Scientific Method Scientific Models – Natural Law • As scientists observe nature, they often see that the same observation applies to many different systems. • A generally observed behavior is formulated into a statement called a natural law. • A natural law describes a behavior in nature. • For example, the observation that the total mass of materials in not affected by a chemical change in those materials is called the law of conservation of mass.
http://www.youtube.com/watch?v=LKFanG5s01M • 3.3 minute video on Scientific Method
The Scientific Method Laws vs. Theories • A natural law is a summary of observed (measurable) behavior, whereas a theory is an explanation of behavior. • A law summarizes facts. • a theory (model) is an attempt to explain why it happens. http://austringer.net/wp/index.php/2009/07/03/another-look-at-law-and-theory/
Matter • Matter – anything that has mass and takes up space. • What is NOT matter; • Light • Heat • Sound
How are weight and mass different? • To understand the differences we need to compare a few points: • 1) Mass is a measurement of the amount of matter something contains, while Weightis the measurement of the pull of gravity on an object. • 2) Mass is measured by using a balance comparing a known amount of matter to an unknown amount of matter. Weight is measured on a scale. • 3) The Mass of an object doesn't change when an object's location changes. Weight, on the other hand does change with location. • http://www.youtube.com/watch?v=1whMAIGNq7E 3 min song
Law of Conservation of Mass • In a chemical reaction matter is neither created nor destroyed. http://www.youtube.com/watch?v=dExpJAECSL8 http://www.sciencelearn.org.nz/Contexts/Nanoscience/Science-Ideas-and-Concepts/Chemical-reactions-and-catalysts
http://www.youtube.com/watch?v=x9iZq3ZxbO8&feature=related Antoine Lavoisier • Father of modern chemistry • Creator of metric system • Discovered Law of Conservation of Mass
States of Matter • Solid – definite shape and volume; very hard to compress; particles are packed very tightly. • Liquid – indefinite shape and has definite volume; hard to compress; particles close together but with lose, not orderly arrangement • Gas – takes the shape and volume of a container; easily compressible; particles are spaced furthest apart
States of Matter Definite Volume? Definite Shape? Temp. increase Com-pressible? Small Expans. Solid YES YES NO Small Expans. Liquid NO NO YES Large Expans. Gas NO NO YES
States of Matterhttp://www.middleschoolchemistry.com/multimedia/chapter2/lesson5
Other States of Matter • Plasma - A plasma is a super hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. (Because plasmas are made up of electrically charged particles, they are strongly influenced by electric and magnetic fields while neutral gases are not.) • Bose-Einstein – A super cold condensed gas where the atoms are at their lowest excitation state. (Only state of matter to be discovered in your parents’ lifetime.)
http://www.youtube.com/watch?v=s-KvoVzukHo&feature=autoplay&list=PL727EDC279E68643D&playnext=1http://www.youtube.com/watch?v=s-KvoVzukHo&feature=autoplay&list=PL727EDC279E68643D&playnext=1 • States of mater video
Properties of Matter Chemical and Physical Properties • Chemical Properties – potential to change into a new substance. • reactivity • energy content • Physical Properties – properties that can be observed and measured; determined without destroying matter • Boiling point • Freezing Point • Melting point • Color and Odor • Density
Classification of Matter • Pure Substances a. Elements b. Compounds • Mixtures a. Homogeneous and solutions b. Heterogeneous
Energy Types • Kinetic Energy – Energy a body has because it is in motion. • Potential Energy - Potential energy is stored energy--energy ready to go. • Energy can be transferred from potential to kinetic and between objects. http://www.youtube.com/watch?v=vl4g7T5gw1M 2 min song
Elements vs. Compounds http://www.youtube.com/watch?v=d0zION8xjbM Element Song
Elements • Simplest form of matter • Cannot be broken down into simpler parts and still maintain the same properties. • Cannot be broken down into simpler substances by chemical means • Elements are composed of atoms
Compounds • A substance made of two or more elements chemically combined in fixed proportion • Compounds can be broken down into simpler substances by chemical methods. • http://www.youtube.com/watch?v=cL6I1O1YHH0&list=PL727EDC279E68643D&index=8&feature=plpp_video2 min
Mixtures – made up of two or more compounds or elements and can be separated by physical methods. Homogeneous Mixture – look the same throughout • Kool-aid Gasoline • Tea and coffee Milk • Air • Blood
Heterogeneous Mixtures – mixture is not the same throughout; can see visible bits and pieces. • Noodle Soup • Gravel • Soil • Salad Dressing • Oil and Water • Ink
Compound or Mixture? How can you tell? • If the composition of the material is fixed then it is a compound. • If the composition of the material canvary, then it is a mixture. EX – Milk; has several types Gasoline; has several octanes
Compound or Mixture Compound Mixture One kind of piece- Molecules More than one kind - Molecule or atoms Making is a chemical change Making is a physical change Only one kind Variable composition
Physical Separation of Mixtures Only a physical change - no new matter • Filtration- separate solids from liquids with a barrier • Distillation-separates liquids because of different boiling points • Heat mixture • Catch vapor in cooled area • Chromatography-different substances are attracted to paper or gel, so move at different speeds
Element Compound Mixture Which is it?
Physical vs. Chemical Change Physical Change – a change that alters the appearance of a substance but not its chemical composition. • Melting ice • Cutting wood • Evaporating alcohol • Breaking glass • Polishing metal
Chemical Changes – a change where a new form of matter is made; also called a chemical reaction. Cannot be reversed • Burning wood • Rotting food • Glow sticks • Cooking food • Fireworks • Making cheese or yogurt
Signs of a Chemical Reaction • Heat is produced • Gas is produced • Color change • Precipitate is formed • Solution turns colder • Light is produced http://www.youtube.com/watch?v=8RmVwz2fNGc Precipitation reaction
Metric System of Measurement King Henry Died By Drinking Chocolate Milk BASE kilo-hecto-deka-UNITdeci-centi-milli- • 100 10 1 1 1 1 10 100 1000 103 102 101 1 10-1 10-2 10-3
1 2 3 MetersLitersGrams How do you use the “ladder” method? 1st – Determine your starting point. 2nd – Count the “jumps” to your ending point. 3rd – Move the decimal the same number of jumps in the same direction. Starting Point Ending Point __. __. __. 2 3 1 Ladder Method KILO1000Units HECTO100Units DEKA10Units DECI0.1Unit CENTI0.01Unit MILLI0.001Unit 4 km = _________ m How many jumps does it take? 4. = 4000 m
Compare using <, >, or =. 56 cm 6 m 7 g 698 mg Conversion Practice Try these conversions using the ladder method. 1000 mg = _______ g 1 L = _______ mL 160 cm = _______ mm 14 km = _______ m 109 g = _______ kg 250 m = _______ km
Metric Conversion Challenge Write the correct abbreviation for each metric unit. 1) Kilogram _____ 4) Milliliter _____ 7) Kilometer _____ 2) Meter _____ 5) Millimeter _____ 8) Centimeter _____ 3) Gram _____ 6) Liter _____ 9) Milligram _____ Try these conversions, using the ladder method. 10) 2000 mg = _______ g 15) 5 L = _______ mL 20) 16 cm = _______ mm 11) 104 km = _______ m 16) 198 g = _______ kg 21) 2500 m = _______ km 12) 480 cm = _____ m 17) 75 mL = _____ L 22) 65 g = _____ mg 13) 5.6 kg = _____ g 18) 50 cm = _____ m 23) 6.3 cm = _____ mm 14) 8 mm = _____ cm 19) 5.6 m = _____ cm 24) 120 mg = _____ g
Density Density = mass (grams or kg) / volume (cm3 or ml) d = m/v or m = d x v or v = m/d Density is a physical property of matter. http://www.youtube.com/watch?v=BmbkBUgyTQY Density of liquids
Platinum Mercury Aluminum DENSITY– expressed as mass per unit volume 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3
Density is NOT Constant When temperatures increase – materials expand (their volume increases) – DENSITY DECREASES When temperatures decrease – materials contract (their volume decreases) - DENSITY INCREASES ONE MAJOR EXCEPTION - Water
ProblemA piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).
Strategy 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density.
SOLUTION 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density. (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3 Note only 2 significant figures in the answer!
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?