Introduction: Matter and Measurement Chapter 1 Introduction: Matter and Measurement

Classification of Matter Matter is anything occupying space and having mass Matter exists in 3 physical states (or phases) 1. Solid – rigid with fixed volume and shape 2. Liquid – definite volume with shape of the container 3. Gas – no fixed volume or shape, highly compressible Mixture have variable composition (maintain individual properties) Homogeneous mixture – visibly indistinguishable Heterogeneous mixture – visibly distinguishable Solution is a homogeneous mixture

Physical properties include color, odor, density, melting point, boiling point, and hardness. Mixture can be separated into pure substances by physical properties: distillation, filtration, chromatography, or a magnet Pure substance, element or compound require chemical processes to break down. Intensive properties depend on the chemical, not the amount of chemical. Extensive properties depend on the amount of chemical, the mass or volume.

Physical change: A change in physical appearance but NOT composition. Chemical change: The atoms are transformed into a chemically different substance. Color change 2. Temperature change 3. Formation of a gas 4. Formation of a precipitate

Elements in the Earth System (% mass in Crust, Ocean, & Atmosphere) Oxygen 49.5 % Silicon 25.7 % Aluminum 7.50 % Iron 4.71 % Calcium 3.39 % Sodium 2.63 % Potassium 2.40 % Magnesium 1.93 % Hydrogen 0.87 %

Elements in the Human Body Your body is worth less than $1.00 Oxygen 65.0 % Carbon 18.0 % Hydrogen 10.0 % Nitrogen 3.0 % Calcium 1.4 % Phosphorus 1.9 % Magnesium 0.50 % Potassium 0.34 % Sulfur 0.26 % Sodium 0.14%

Formulate a hypothesis – possible explanation Scientific Method Make an observation Qualitative – observation using descriptive words Quantitative – observation using numbers and units Formulate a hypothesis – possible explanation Perform an experiment to test the hypothesis and gather data Analyze the data Formulate a conclusion based on data Scientific Theory – A model or set of tested hypothesis that gives an overall explanation of some natural phenomenon, an interpretation. Scientific Law – Summarizes what is happening.

Metric System (System International SI) Mass – kilogram (Kg) 1 gram = mass of 1 mL of H2O @ 4 oC Length – meter (m) length that light travels in a vacuum in 1/299,792,458 sec Time – second (s) Temperature – Kelvin or Celsius Electric current – ampere (A) Amount of substance – mole (mol) Volume – liter (L) 1 liter = a cube 10 cm / side volume of 1 cm3 = 1 mL * 1 g H2O = 1 cm3 = 1 mL Density = mass/volume (g/mL or g/cm3)

Prefixes used with the metric system page 16 your text

Temperature conversions K = oC + 273 ( oF – 32 ) 5/9 = oC Heat always flows from the higher to the lower temperature substance

Uncertainty in Measurement: A measurement can be expressed with all certain digits plus one more uncertain. Measurements always have some uncertainty. The degree depends on the precision of the measuring device. 50 mL beaker (markings every 10 mL) 10 certain 100 mL graduated cylinder (markings every 1 mL) 10.0 certain volumetric pipet (at ring on neck) 10.00 certain

Which of the above targets are accurate and/or precise? Accuracy is the “closeness” of a measured value to the true or accepted value. Precision is the degree of reproducibility of a measured quantity. How closely individual measurements agree with one another. Which of the above targets are accurate and/or precise?

Significant figures means all certain numbers plus one uncertain Significant figures means all certain numbers plus one uncertain. Page 23 - 25 Nonzero integers count Zero leading zero don’t count 0.0025 captive zero count 1.008 0.04097 tailing zero count only if number contains a decimal point 360,000 0.05870 5,400.0 Exact numbers count (example 3 apples count) Multiple or division: answer has same number of significant figures as least precise measurement used in calculation Addition or subtraction: answer has same number of decimal places as least precise measurement used in calculation In a series of calculation, carry the extra digits through to the final result, then round!

Dimensional analysis is a method of multiplying by a factor equivalent to 1, to change the units. Convert 15 Km/L to mi/gal

Density = mass/volume (units of g/mL or g/cm3) A block of wood has a mass of 2.52 Kg. What is the density of the wood? 51 mm 1.08 m 6.2 cm

A chemist, trying to identify the main component of a compact disc cleaning fluid, finds that 25.00 cm3 of the substance has a mass of 19.65 g at 20 oC. What is the main component? Compound Density @ 20oC Chloroform 1.492 g/cm3 Diethyl ether 0.714 Ethanol 0.789 Isopropyl alcohol 0.785 Toluene 0.867

Seawater has a density of 1. 03 g/mL. 3 Seawater has a density of 1.03 g/mL. 3.50% of seawater by mass is salt. How many liters of seawater must be evaporated to give 75.0 g salt? Start with known!

Precision can be determined by Relative Average Deviation (RAD) RAD% = ( average deviation ) 100 Measures random error A small RAD means that you precision is high! Accuracy % = ( ltrue value – average measured value l ) average value (100) true value

In a titration, a student measures the concentration of an acid four times. What is the RAD? Results deviation 0.1025 M - = 0.1018 - = 0.1020 - = 0.1024 - = What is the accuracy % is the true value is 0.1014 M?