Introduction to Organic in addition to Biochemistry (CHE 124) What is Chemistry What is the scientific Method Scientific Method What is Matter
Moulitsas, Markos, Founder & Blogger has reference to this Academic Journal, PHwiki organized this Journal Introduction to Organic in addition to Biochemistry (CHE 124) Reading Assignment General, Organic, in addition to Biological Chemistry: An Integrated Approach 4rd. Ed. Ramond Chapter 1 Science in addition to Measurements Answers to odd numbered problems in textbook are found in the books index. What is Chemistry Chemistry – the study of matter in addition to the changes that it undergoes (e.g. reactions). Chemistry is the central science. It unifies the sciences in biology, physics, engineering, medicine, pharmacy, etc. What is the scientific Method The scientific method is a way of gathering in addition to interpreting in as long as mation about chemistry (see next slide). Hypothesis tentative explanation (educated guess) as long as observations in addition to known facts. Theory an experimentally tested explanation of an observed behavior. (a well tested hypothesis) Law statement that describe things that are consistently in addition to reproducibly observed. (a well tested theory)
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Scientific Method What is Matter Matter anything that has mass in addition to occupies space. Weight measure of gravitational pull against matter. Mass measure of amount of material. Phases of Matter Solids Fixed volume in addition to shape Liquids Fixed volume, indefinite shape. A liquids takes on the shape of the container. Gases Indefinite shape in addition to volume. A gas takes on both the shape in addition to volume of the container. Properties of Substances Every pure substance has its own unique set of properties that serve to distinguish it from all other substances. Look them up in the chemical literature These properties are classified as: Intensive properties independent of amount of substance. ( E.g. m.p., b.p., density) Extensive properties dependent on amount of substance. (e.g. mass, volume) Chemical properties observed when the substance takes part in a chemical reaction becomes a new substance E.g. Heating Mercury (II) oxide to produce oxygen. Does the substance react with oxygen Physical properties No chemical change is required Examples: Melting point (m.p.) temp. when substance changes from solid to liquid. Boiling point (b.p.) temp. when substance changes from liquid to gas. Density = Solubility = amount of solute that dissolves in a give amount (100g) of solvent at a specific temp. Color
What is Energy Energy The ability to do work in addition to / or to transfer heat. Potential energy stored energy Kinetic energy energy of motion Measurements Chemistry is a quantitative science. We use the SI system of measures. SI Units International System of Measure Common name: the metric system Based on the decimal (powers of ten) Kg, L, K, °C English system is used in the United States. Measuring Length SI unit of Length = meter (m) Definition of meter – the distance light travels in 1/299,792,458 of one second 1 m = 39.37 in. English units mile (m), yard (yd.), foot (ft.),inch (in.) Instruments used to measure length Meter stick Micrometer
Measuring Volume SI Unit of Volume = Liter (L) Volume is derived from SI unit of length. Units of volume cubic meter (m3) = 1000 L cubic centimeter (cm3 or cc)= milliliters (mL) English Units Gallon (gal.), quart (qt.), pint (pt.), cup (c), teaspoon (tsp.) , table spoon (tbsp.), fluid ounce (oz.) Instruments used to measure volume Graduated cylinder, pipet or buret, digital micropipet Measuring Mass SI Unit = kilogram (kg) Definition of kg The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. Kilogram (kg) = 1000 g 1 gram (g) = 1000 mg English Units Ton (ton.), pound (lb.), ounce (oz.) Instruments used to measure mass Balance Scale Mass vs Weight Mass Amount of matter in a sample. Weight The effect of gravity on the matter.
SI Units Source: http://physics.nist.gov/cuu/Units/units.html Derived SI Units Derived SI Units with Special Names
Metric Prefixes English Conversions English to Metric Conversions
Typical Conversions Problems The dosage on a bottle of medicine reads: Take 2 tablespoons every twelve hours. Convert this volume to mL. The box at the pet store states: Aquarium volume is 55 gal.. Convert this volume to liters. The distance (length) from Clinton to Vicksburg is appr. 32 miles. What is this distance in cm A marathon is defined as 42.195 km. What is this distance in miles Measuring Temperature Factor that determines the direction of heat flow SI units = °C or K Fahrenheit (°F) Named after German instrument maker Daniel Fahrenheit (1686 -1736) Celsius (°C) (old name centigrade) Named after Swedish astronomer Anders Celsius (1701-1744) Kelvin (K) Do not use (°) or degree in relation to K. Defined as 1/273.16 of the difference between the lowest attainable temp. (0K) in addition to the triple point of water (0.01 °C) Instruments to measure Mercury thermometer Mercury exp in addition to s in addition to contracts as temperature changes. Tube contains only 2% of the Hg in thermometer. Digital thermometer Water boils = 212 °F = 100 °C = 373.15 K Water freezes = 32 °F = 0 °C = 273.15 K Triple point is the temp. /pressure combination at which water is capable of coexisting as a solid, liquid in addition to gas. Converting Temperature Scales Comparing °F to °C 0 °C is 32 °F Freezing point of water 100 °C is 212 °F Boiling point of water There are 180 Fahrenheit degrees as long as every 100 Celsius degrees, so each °C is 1.8 times larger than each °F Comparing °C to K Celsius degree in addition to Kelvin degree are the same size.
Scientific Notation A way of dealing with very large or very small numbers. Show examples on the board: Avogadro number 6.022 X 1023 83,000 0.000056 See table 1.3 p.12 Accuracy vs Precision Accuracy How close a reported value is to the real value. (see next slide about error). Precision A measure of how close repeated measurements are to one another. Uncertainties in Measurements How much solution is in the large graduated cylinder How much solution is in the small graduated cylinder Do these two measurements have the same uncertainty
Uncertainties in Measurements Three volume measurements with their uncertainties Large graduated cylinder, 8 ± 1 mL Small graduate cylinder, 8.0 ± 0.1 mL Pipet or buret, 8.00 ± 0.01 mL To denote how much uncertainty is in a measurement, Significant figures are used. Significant Figures Every measurement carries uncertainty All measurements must include estimates of uncertainty with them There is an uncertainty of at least one unit in the last digit Text convention Uncertainty of ± in the last digit is assumed but not stated Significant Figures Significant figures are meaningful digits in measurements In 8.00 mL, there are three significant figures In 8.0 mL, there are two significant figures In 8 mL, there is one significant figure Ambiguity in Significant Figures Consider the measurement, 500 g If the measurement was made to the nearest 1 g, all three digits are significant If the measurement was made to the nearest 10 g, only two digits are significant Resolve by using scientific notation 5.00 X 102 g 5.0 X 102 g See Table 1.5 p. 17
Rounding Rounding off numbers If the first digit to be discarded is 5 or greater, round up If the first digit to be discarded is 4 or smaller, round down Significant Figures in Calculations Addition in addition to Subtraction Count the number of decimal places in each number Round off so that the answer has the same number of decimal places as the measurement with the greatest uncertainty (i.e., the fewer number of decimal places). Multiplication in addition to Division When multiplying or dividing two numbers, the answer is rounded to the number of significant figures in the less (or least in the case of three or more) measurements 2.40 X 2 = 5 Exact Numbers Exact numbers carry an infinite number of significant figures Exact numbers do not change the number of significant figures in a calculation Example: The numbers 1.8 in addition to 32 in the conversion between Fahrenheit in addition to Celsius Dimensional Analysis / Factor Label / Converting Units In many cases throughout your study of chemistry, the units (dimensions) will guide you to the solution of a problem A correct answer must have the NUMBER in addition to UNITS! Conversion factors are used to convert one set of units to another Only the units change Conversion factors are numerically equal to 1 1L = 1000 cm3 Choose a conversion factor that puts the initial units in the denominator The initial units will cancel The final units will appear in the numerator
Specific Gravity Relates density of a substance to that of water. Measured using refractometeres, hydrometers or test strips. Used to determine acid level in car batteries antifreeze level in car radiators alcohol content in beer in addition to wine Urine to diagnose kidney problems Temperature must be specified since the density of the substance in addition to water vary, but not necessarily at the same rate. Specific Gravity = Density of substance = 0.785 g/mL = 0.785 Density of water 1.00 g/mL Specific Heat Relates energy (in calories), mass (in grams), in addition to temperature (in degrees Celsius). Units = cal / g °C Relates the mass, temperature, in addition to energy.
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