SCI 100 Midterm Notes

What is Science?

• Scientific method is the process of gaining knowledge by testing and observation

  • “a way of thinking much more than it is a body of knowledge”

  • question, hypothesis (+ prediction), experiment, data analysis, conclusion, communication

• The purpose of science is to build knowledge about the world

• Hypothesis vs prediction

  • hypothesis: a yes or no answer, just an attempt to answer the question you’re asking; can be tested

  • prediction: attempt to describe the outcome/what happens in the experiment and is typically related to the hypothesis

• Controls

  • purpose: plays the role of a constant factor in the experiment to compare to the dependent variable or experiment results

  • types of control groups

    • positive control: group that is treated with a known response and gives the expected result

    • negative control: group that does not get treatment, staying the same and not showing any change in the experiment

• Dependent vs independent variables

  • dependent variable is what is being tested in the experiment, DEPENDENT on the independent variable

  • independent variable is what is being changed in the experiment for the dependent variable

  • cause (independent) and effect (dependent)

How Clean is Your Water: Water Quality

• The 8 parameters to calculate a Water Quality Index

  • temperature

    • measure change in temperature

      • affects how much of other substances can dissolve

  • pH

    • measures acidity (<7) or base (>7) of substance

    • 0-14

    • change in one pH unit = TENFOLD increase/decrease in acidity

  • dissolved oxygen

    • required for aquatic organisms’ survival

    • fluctuations: photosynthesis, wind, temperature

  • fecal coliform bacteria

    • measures contamination in water

    • gut bacteria found in warm-blooded animals

  • total nitrates

    • necessary for life

    • can cause eutrophication if too much

    • come from sewage and fertilizers

    • more limiting in saltwater vs freshwater

  • total phosphates

    • necessary for life

    • a limiting factor in freshwater

      • constrains a population’s size

    • can cause algal blooms and eutrophication

  • turbidity

    • measure of water clarity

    • suspended water particles can absorb sunlight and increase water temp.

    • is a BLOCKER

      • can block fish’s gills

      • can block sunlight from plants

  • conductivity

    • measure of water’s ability to make electricity ⚡️

    • more dissolved ions = more conductivity ↑↑

      • pure water is NOT a good conductor

• Biological importance: benefits the environment and public health; protects aquatic life and prevents dehydration and malnourishment with good water quality

• Water hardness is the dissolved mineral content in the water (e.g., calcium and magnesium)

• Hard vs soft water

  • hard water has more minerals; soft water has less

  • soft water is more slippery

• A watershed is land mass where water moves through on its way to somewhere else

  • rivers help water move in a watershed and are ALSO part of it

  • UMBC’s specific watershed: Herbert Run; general watershed: Chesapeake Bay

Estuaries: Solutions, Eutrophication

• An estuary is a place where salt water and freshwater meet and mix

  • e.g., Chesapeake Bay

  • ecological importance: provides clean water by filtering rivers before they go in oceans

• Standard curve: a graph of known concentrations of a substance vs a measurable factor

  • importance: compares a unknown sample to known solutions to determine the unknown

  • R2 = the coefficient of determination

    • provides info about how well the model fits with the data

• Simbio review

  • eutrophication is excessive primary production when water receives too many nutrients

    • causes harmful algae blooms and fish kills

  • causes of phytoplankton growth

    • dissolved oxygen: is needed for aquatic life survival but levels become low in the water from the large populations of primary producers

    • phosphate level: is increased for primary producers to also increase

Water Chemistry

• An element is a substance that cannot be broken down

  • parts of an atom: proton, neutron, electron, nucleus

• Bonds

  • ionic: bond where electrons are GIVEN AWAY/TRANSFERRED

  • covalent: bond where electrons are SHARED

  • polar covalent: bond where electrons are shared UNEQUALLY due to charge

    • “popular table”

  • hydrogen: the force between the ends of neighboring molecules

    • opposites attract; one end is slightly negative and one is slightly positive

• Valence electrons are electrons on the outermost shell of an atom

  • importance: indicate an atom’s chemical properties and if they lose/gain/share an electron

• Polar covalent and hydrogen bonds are important in water/H2O

  • polar covalent bonds hold the water molecule together

  • hydrogen bonds hold water molecules to other water molecules

• Unique properties of water

  • is a universal solvent

    • will dissolve most compounds

  • has cohesion (clings to itself) and adhesion (clings to other things)

  • has a high specific heat

    • importance: makes water a good insulator and allows oceans to regulate coastal climate

  • has a high heat of vaporization

    • importance: makes water a good coolant and is depended by earth’s heat transfer

  • LESS dense as a solid than a liquid

    • importance: allows ice to float and is related to seasonal turnover

• Temperature and water density: the warmer the water ↑, the more space it takes up ↑, the less dense water becomes ↓

  • aka HOT = LEAVE ME ALONE → less dense/strong; COLD = GET CLOSE TO ME → more dense/strong

  • greatest density at 4ºC

  • ecological importance: makes colder water to sink, allowing aquatic life to live in warmer water during colder seasons

• Process of seasonal turnover in a temperate freshwater bond (aka CERA pond)

  • water in lakes STRATIFY/form layer due to the sun’s heat and changing seasons

    • winter: top layer stays at 0ºC while water below stays warm

    • spring: surface heats up and warm water rises

    • summer: top layer warms up and is separated by the transition layer from cooler/denser waters of the bottom layer

    • fall: top layer starts to cool, get dense, and descend

How is Baltimore (City) Water Treated?

• Pre-chlorination

• Coagulation/flocculation

• Sedimentation

• Filtration

• Fluoridation (@ 1ppm)

• Disinfection (post chlorination; 0.2-1ppm)

• Corrosion control treatment

How is Wastewater Treated?

• Pretreatment

  • screens/filters large objects

• Primary treatment

  • removes phosphorus and suspended organic particles settle out

• Secondary treatment

  • wastewater is treated with bacteria

    • decomposes organic matter in water

• Additional sedimentation process

  • filtered through sand beds and treated with chlorine

    • disinfects water and prevents algal growth

    • is removed after