[DOST] CHEMISTRY

• chemistry: study of matter, its composition, properties, changes it undergoes, and the energy involved in those changes
• accuracy: how closely are individual measurement agree with the correct, or "true" value
• precision: measure how closely individual measurements agree with each other
• HIGH PRECISION, LOW ACCURACY: A student conducted an experiment with 6 trials. The experimental values that were obtained were 2.59, 3.01, 3.05, 3.44, 2.67, and 3.12. If the theoretical value is 8.00, this describes the values accumulated by the student.
• Kilo, Hecto, Deca, (UNIT), Deci, Centi, Milli
• DIMENSIONAL ANALYSIS: (starting amount x)(equal amount y/x) = converted
• celsius to farenheit: F=(9/5)C + 32
• farenheit to celsius: (5/9)(F-32)
• celsius to kelvin: C + 237
• kelvin to celsius: K-273
• -40 degrees: The level that Fahrenheit and Celsius will give the same reading.
• 0.1L : amount of liters in a 100cm^3 cylindrical shell
• LAW OF CONSERVATION OF MASS

  • the total mass of the products of a chemical reaction is the same as the total mass of the reactants entering into the reaction
  • total mass of products = total mass of reactants
  • mass input = mass output
• LAW OF CONSTANT COMPOSITION

  • all samples of a compound have the same composition or proportion
  • also known as Law of Definite Proportions
• LAW OF MULTIPLE PROPORTIONS

  • If two elements A and B combine to form more than once compound, the masses of B that can combine with the given mass of A are in the ratio of small whole numbers.
• CO and CO2

  • When broken down, the respective masses of the elements stay in the same ratio.
  • The ratio of the masses is small whole numbers.
• MATTER AND ITS PROPERTIES

  A) MATTER

  B) MIXTURE

  C) PURE SUBSTANCE

  D) HOMOGENOUS

  E) HETEROGENEOUS

  F) COLLOIDS

  G) SUSPENSIONS

  H) COMPOUND

  I) ELEMENT

  
• PHYSICAL PROPERTIES: color, odor, hardness, density, boiling point, melting point
• CHEMICAL PROPERTIES: the way a substance may change or react to form another substance
• INTENSIVE: do not depend on the amount of sample being examined (ex. color, boiling point, pressure, molecular weight, and density)
• EXTENSIVE: depend on the amount of sample (mass and volume)
• PHASE CHANGES OF MATTER

  A) liquid

  B) solidification

  C) melting

  D) sublimation

  E) deposition

  F) vaporization

  G) condensation

  
• condensation: kind of phase change occurs when a water vapor from plants turns into dew drop
• PHYSICAL SEPARATION

  • filtration - uses membrane considering the particle size
  • distillation - employs the ability of substance to form gases
• solution: uniform dispersion of substances
• solute: dissolved in solvent
• molarity: moles per liter of solution

  • M = moles solute/liters solution
• molality: moles per kilogram of solvent

  • m = moles of solute/ kg solvent
• normality: number of equivalent solute per solution

  • N = equivalents of solute/liters per solution
• % by mass : mass of component of a solution per total of mass solution

  • %w/w: mass of component of a solution/total mass of solution
• % by volume: volume of a component of a solution per total volume of solution

  • %v/v: volume of component of a solution/total volume of solution
• FACTORS AFFECTING SOLUBILITY

  • pressure: solubility of gases
  • temperature: solubility increases as the temperature increases
• INTERMOLECULAR FORCES OF ATTRACTION: forces that hold atoms together
• LDF

  • present in ALL substances
  • temporary dipole moment
  • present in polar and nonpolar substances
• DP-DP INTERACTIONS

  • permanent dipole moment
  • present in POLAR substances only
• H-BONDING

  • special type of dipole-dipole interaction
  • STRONGEST IMFA
  • hydrogen atom and N, O, F
• HIGHER IMFA:

  • higher boiling point
  • higher surface tension
  • higher melting point
  • higher latent heat of fusion, vaporization, sublimation
• IDEAL GAS EQUATION: PV=nRT
• R (Universal Gas constant) = 0.08206 atm
• BOYLE'S LAW: volume is INVERSELY proportional to pressure

  • P1V1=P2V2