Presentation on theme: "Matter and Measurement Chapter 1. The Scientific Method 1. Observations – something that is witnessed and can be recorded Qualitative Qualitative Quantitative."— Presentation transcript:
The Scientific Method 1. Observations – something that is witnessed and can be recorded Qualitative Qualitative Quantitative Quantitative 2. Hypothesis 3. Experiment 4. Theory 1. 1. Tested hypotheses that explains WHY nature behaves in a certain way 2. 2. Change as more info become available
Is the method used to determine the Kentucky Derby winner a qualitative measurement or a quantitative measurement? Explain.
Classification of Matter Matter – anything that takes up space and has mass 1. Solids 2. Liquids 3. Gases What can you tell me about the shape, volume, and compressabilty of the above?
Mixtures – matter of variable composition Mixtures – matter of variable composition Homogeneous: Homogeneous: Uniform in composition; having visibly indistinguishable parts Uniform in composition; having visibly indistinguishable parts Heterogeneous: Heterogeneous: Not uniform in composition; visually distinguishable parts Not uniform in composition; visually distinguishable parts
Pure Substances Elements: Elements: cannot be decomposed into simpler substances Compounds: Compounds: Two or more elements interacting with one another Law of Definite proportions: Law of Definite proportions: The elemental composition of a pure compound is always the same
Properties of Matter Physical Properties 1. Measured without changing the identity and composition of substance 2. Includes color, odor, density, melting/boiling point, and hardness Chemical Properties 1. Describes the way a substance may change or react to form other substances
Intensive Properties 1. Doesn’t depend on the amount in a sample 2. Used to identify substances 3. Ex: temperature, melting point, density… Extensive Properties 1. Depends on the quantity of the sample 2. Ex: mass, volume …
Scientific Notation exponential notationAlso known as exponential notation Way to write very small and very large numbers using powers of ten. Answers in Sci. Notation should have ONLY 1 # (1-9) to the left of the decimal 3.6 x 10 4 = 36 000 5.8 x 10 -3 = 0.0058 Why would that be useful?
Multiplication 1)Multiply the Coefficients 2)Add the Exponents (3.0 x 10 4 ) x (2.0 x 10 2 ) = (3.0 x 2.0) x 10 4+2 = 6.0 x 10 6
Division 1)Divide the coefficients 2)Subtract theexponents 2)Subtract the exponents. 3.0 x 10 4 = 3.0 x 10 4-2 = 1.5 x 10 2 2.0 x 10 2 2.0
Fixing the exponent: Move the decimal 1 space to the Left for every time you ADD ONE to the exponent Move the decimal 1 space to the Left for every time you ADD ONE to the exponent Move the decimal 1 to the Right for every time you SUBTRACT ONE from the exponent Move the decimal 1 to the Right for every time you SUBTRACT ONE from the exponent
Addition and Subtraction 1)Make the exponents the same. (pick highest exponent) 2) Add or Subtract the coefficients (5.40 x 10 3 ) + (6.0 x 10 2 ) = 0.60 x 10 3 (5.40 x 10 3 ) + (0.60 x 10 3 ) = 6.00 x 10 3
Units of Measurement Measurements include two parts: a Number and Scale (units) … a number without units is worthless! Measurements include two parts: a Number and Scale (units) … a number without units is worthless!
The Fundamental SI Units Physical QuantityUnit Abbreviation MassKilogramkg LengthMeterm TimeSeconds (sec) TemperatureKelvinK Amount of substanceMolemol Electric currentAmpereA Luminous intensityCandelacd
Standard SI prefixes for Chemistry Prefix Unit Abbreviation Exponent (numerical value compared to base) MegaM 10 -6 KiloK 10 -3 Decid 10 1 Centic 10 2 Millim 10 3 Micro 10 6 Nanon 10 9 Picop 10 12
Temperature Celsius ( o C) and Kelvin (K): Celsius ( o C) and Kelvin (K): 1. K = o C + 273 2. o C = K – 273 3. The size of the temperature unit is the same Fahrenheit Fahrenheit 1. o C = (5/9)( o F – 32) 2. o F = (9/5)( o C) + 32
Density The amount of mass in a unit of volume of a substance Density = Mass / Volume
Uncertainty in Measurement A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty because… A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty because… 1. it is performed with instruments 2. no instrument can read an infinite number of decimal places
is a measure of how close a measurement comes to the actual or true value. is a measure of how close a series of measurements are to one another. accurateprecise If all three darts were on the bullseye, you would be both accurate and precise.
Errors Random Error (Indeterminate Error) 1. Measurement may be high or low 2. Caused by interpretation of uncertain digit or procedural ineptness Systematic Error (Determinate Error) 1. Always occurs in the same direction 2. Caused by poor technique or incorrect calibration (gun sight set high/low; balance improperly zeroed, thermometer improperly marked
accepted value - experimental value accepted value accepted value = the correct value experimental value experimental value = the value measured in the lab
error accepted value is the absolute value of the error divided by the accepted value, multiplied by 100%. % Error = error x 100% accepted value
All of the digits that are known, plus a last digit that is estimated. Sig. Figs. Matter all year, on all assignments, make sure to follow rules! For AP test… good rule of thumb to use 3 significant figures (graders give you a +/- 1 cushion)
1) Nonzero digits are always significant. ex: 1, 2, 3, 4…9 Rules to Determine if a digit is Significant:
2) Zeros between nonzero digits are significant Ex: 2005, 107, 250000023 4 3 9
Rules to Determine if a digit is Significant: 3) Leftmost zeros appearing in front of nonzero digits are NOT SIGNIFICANT. They act as placeholders. Ex: 0.007, 0.12, 0.000434 123
Rules to Determine if a digit is Significant: 4) Zeros at the end of a number and to the right of a decimal point are always significant. Ex: 34.00, 10.00, 0.400 4 43
Rules to Determine if a digit is Significant: 5) Zeros at the end of a whole number are not significant. Ex: 10, 100, 4500 … 1 12
Pacific/Atlantic Rule If a decimal is Present, start on the Pacific side of the number and every number counts after the first non- zero digit If a decimal is Present, start on the Pacific side of the number and every number counts after the first non- zero digit If a decimal is Absent, start on the Atlantic side of the number and every number counts after the first non-zero digit. If a decimal is Absent, start on the Atlantic side of the number and every number counts after the first non-zero digit.
A) 5000 = B) 0.0234 = C) 10.0052 = D) 25.000 = 1 sig. fig. 3 sig. figs. 6 sig. figs. 5 sig. figs.
Round the answer to the same number of significant figures as the measurement with the least number of significant figures. 7.55 x 0.34 = 2.567 = 2.6
CaluculationCalculator SaysAnswer 3.24m x 7.0 m22.68m 2 10.2 m 2 100.0g / 23.7g4.21940 g/cm 3 4.22 g/cm 3 0.02cm x 2.371cm 710m / 3.0s 0.04742cm 2 236.66667 m/s 0.05cm 2 240 m/s
Round the answer to the same number of decimal places as the measurement with the least number of decimal places. 1.2 + 3.52 + 2.431 = 7.151 = 7.2
CaluculationCalculator SaysAnswer 3.24m + 7.0 m 10.24 m 10.2 m 100.0g – 23.73g76.27g 76.3g 0.02cm + 2.371cm 713.1L – 3.872L 2.391cm 709.228L 2.39cm 709.2L
Dimensional Analysis Unit Conversion Questions: Unit Conversion Questions: What unit am I given? What unit am I given? What units must be in my answer? What units must be in my answer? What is (are) my conversion factor(s)? What is (are) my conversion factor(s)?
Full credit will not be given on D.A. problems in which you do not perform the following: 1. Observe sig. fig. rules 2. Label all steps with correct units 3. Correctly label and ID answer 4. Solve problem in manner that can be understood by the reader Why important? Why am I being a jerk about this? Why important? Why am I being a jerk about this?