General Chemistry Concepts: Atoms and Ions
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Questions and Answers

Please identify each of the following as an atom, an element, an ion, a molecule, or a compound:

H2O = Molecule, Compound NH4+ = Ion NH3 = Molecule, Compound H2 = Molecule C6H12O6 = Molecule, Compound H3O+ = Ion F– = Ion Na = Element Ar = Element O22– = Ion

What is an atom?

The smallest particle or unit of an element.

What is a molecule?

A single structure made of two or more atoms.

What is a compound?

<p>A structure made of two or more atoms of different elements.</p> Signup and view all the answers

What are diatomic elements?

<p>Elements that exist as pairs of bonded atoms.</p> Signup and view all the answers

What type of compounds are made of a metal and a nonmetal?

<p>Ionic Compounds</p> Signup and view all the answers

What is the name of the acid for HCl?

<p>Hydrochloric acid</p> Signup and view all the answers

What are polyatomic ions?

<p>Ions that are made up of two or more atoms.</p> Signup and view all the answers

The SI unit for length is the ______.

<p>meter</p> Signup and view all the answers

The prefix 'Kilo-' represents ______.

<p>10^3</p> Signup and view all the answers

List one example of a strong acid.

<p>Hydrochloric acid (HCl)</p> Signup and view all the answers

What is an allotrope?

<p>Molecules with different formulas, whose atoms are all of the same element.</p> Signup and view all the answers

How many seconds are in a day?

<p>86400</p> Signup and view all the answers

How many hours are in a year?

<p>8760</p> Signup and view all the answers

How many kg are there in 7×10^25 μg?

<p>7 × 10^16</p> Signup and view all the answers

How many seconds are there in 5.2 × 10^18 ns?

<p>5.2 × 10^9</p> Signup and view all the answers

Please convert 20 km to cm.

<p>2000000</p> Signup and view all the answers

If you’re going 50 miles/hour, how many feet/second are you traveling?

<p>73.33</p> Signup and view all the answers

On average, hummingbirds fly at 30 miles/hour. Convert this speed to m/s.

<p>13.41</p> Signup and view all the answers

The Brooklyn Bridge is 277 feet tall. Convert this to meters.

<p>84.53</p> Signup and view all the answers

In a vacuum, light travels at a speed of 2.998 x 10^8 m/s. Convert this to miles per hour.

<p>670616629.4</p> Signup and view all the answers

What is the mass in kilograms of 18.5 gallons of gasoline, given that the density of gasoline is 0.70 g/mL?

<p>70.39</p> Signup and view all the answers

What is the density, in g/cm³, of a 1.5 kg cube whose edges are each 5 cm?

<p>12</p> Signup and view all the answers

After carrying out the following operation, the reported value should have how many significant figures? (6.943 cm – 5.81 cm) × 3.23 cm

<p>3</p> Signup and view all the answers

Which measurement below contains 3 significant figures?

<p>II and III</p> Signup and view all the answers

Which of the following has the same number of significant figures as the number 1.00310?

<p>299.782</p> Signup and view all the answers

What is the main knowledge gap addressed in the scientific article?

<p>Levels of contaminants present in various makeup products and what increases contamination risk.</p> Signup and view all the answers

What is the research question of the study?

<p>How much microbial contamination is present in used lipstick, lip gloss, eyeliners, mascaras, and beauty blenders, and what risks do they pose?</p> Signup and view all the answers

Which of the following increases levels of microbial contamination in makeup products? (Select all that apply)

<p>Using expired products</p> Signup and view all the answers

What analyses were used to address the research question?

<p>100 microliters of each solution were inoculated on NA, MSA, SMAC, SAB, and VRBGA.</p> Signup and view all the answers

Beauty blenders were found to be the least contaminated makeup product.

<p>False</p> Signup and view all the answers

How were the results of the study displayed?

<p>The results were displayed via tables and figures, with explanations provided in the results and discussion.</p> Signup and view all the answers

What methods did the researchers suggest to avoid significant levels of contamination?

<p>Not using makeup testers or sharing makeup.</p> Signup and view all the answers

The results of the study did not support the initial hypothesis.

<p>False</p> Signup and view all the answers

What did the authors cite to connect bacteria to makeup contamination?

<p>Previous literature and studies.</p> Signup and view all the answers

What important feature helps in identifying bacterial species?

<p>Shape and arrangement of cells</p> Signup and view all the answers

Which of the following is NOT a benefit of bacteria to humans?

<p>Causing clinical diseases</p> Signup and view all the answers

Which arrangement describes the cells of Streptococcus pyogenes?

<p>Chains resembling a pearl necklace</p> Signup and view all the answers

What is the primary reason for using a microscope in the study of microorganisms?

<p>To distinguish features due to their small size</p> Signup and view all the answers

Which of the following describes the nature of viruses in relation to the domains Eukarya and Bacteria?

<p>They are nonliving entities that multiply within other cells</p> Signup and view all the answers

Which type of microscopy allows for the visualization of living specimens and intracellular structures without killing the organisms?

<p>Phase-contrast microscopy</p> Signup and view all the answers

What is the primary advantage of fluorescence microscopy in medical diagnostics?

<p>It provides quicker diagnoses by visualizing specific infectious agents.</p> Signup and view all the answers

What distinguishes transmission electron microscopy (TEM) from scanning electron microscopy (SEM)?

<p>TEM directs electrons through the specimen, whereas SEM scans the surface.</p> Signup and view all the answers

What happens to living organisms when they are affixed to slides for microscopy?

<p>They die, preventing the observation of intracellular structures.</p> Signup and view all the answers

What is the role of fluorochrome dye in fluorescence microscopy?

<p>It emits visible light of a different wavelength when excited.</p> Signup and view all the answers

What is the primary function of the iris diaphragm in a bright light microscope?

<p>To control the amount of light passing through the specimen</p> Signup and view all the answers

Which of the following describes a binocular light microscope?

<p>It has two eyepieces for viewing</p> Signup and view all the answers

What is the purpose of the objective lenses in a compound light microscope?

<p>To magnify the specimen after light passes through it</p> Signup and view all the answers

Which of the following objective lenses provides the highest magnification?

<p>100X</p> Signup and view all the answers

Where is the light source located in a bright light microscope?

<p>In the base of the microscope</p> Signup and view all the answers

What function does the condenser serve in a bright light microscope?

<p>It gathers and focuses light on the specimen</p> Signup and view all the answers

In a monocular light microscope, what characteristic does it have?

<p>It has one ocular lens</p> Signup and view all the answers

What is the function of placing oil on the slide before using the 100X objective?

<p>It minimizes the loss of light due to refraction.</p> Signup and view all the answers

What factor does NOT influence the resolution of a microscope?

<p>Size of the specimen.</p> Signup and view all the answers

What is the highest resolution achievable with a bright light microscope?

<p>0.2 μm</p> Signup and view all the answers

Which type of microscope is particularly useful for studying unstained, living specimens?

<p>Dark-field microscope</p> Signup and view all the answers

What is the approximate cost of microscopes used in introductory microbiology laboratories?

<p>$1300</p> Signup and view all the answers

How does the numerical aperture of a lens influence microscopy?

<p>It affects the clarity of the image.</p> Signup and view all the answers

What happens to light as it passes from air into glass in microscopy?

<p>It is refracted and some is lost.</p> Signup and view all the answers

Which microscope type would NOT be ideal for bright field microscopy?

<p>Electron microscope</p> Signup and view all the answers

Which statement about the bright light microscope is true?

<p>It is generally less expensive than electron microscopes.</p> Signup and view all the answers

What technique is employed in dark-field microscopy?

<p>Reflection of light at an angle.</p> Signup and view all the answers

Study Notes

Atoms, Ions, and Molecules

  • An atom is the smallest unit of an element.
  • Ions are charged atoms formed by the addition or removal of electrons (e.g., H+ is a cation; H– is an anion).
  • A molecule consists of two or more bonded atoms, which can be identical or different elements.
  • A compound is a specific type of molecule that contains at least two different elements (e.g., H2O).

Classification of Chemical Species

  • H2O: Both a molecule and a compound.
  • NH4+: Ion (specifically a cation).
  • NH3: Molecule (can also be categorized as a compound).
  • H2: Molecule (specifically a diatomic molecule).
  • C6H12O6: Molecule and compound.
  • H3O+: Ion (specifically a cation).
  • F–: Ion (specifically an anion).
  • Na: Element (monatomic).
  • Ar: Element (monatomic).
  • O22–: Ion (specifically an anion).

Elements and Compounds

  • Monatomic elements are single atoms of an element (e.g., Na, Cs).
  • Diatomic elements exist as pairs of atoms (e.g., H2, N2, O2, F2, Cl2, Br2, I2).
  • Allotropes are different structural forms of the same element (e.g., O2 and O3 for oxygen).

Types of Compounds

  • Ionic compounds: Formed from metals and nonmetals (e.g., NaCl, CuCl2). NH4Cl is an exception that is ionic but lacks metals.
  • Molecular compounds: Formed from two or more nonmetals (e.g., H2O, CO2).

Naming Ionic Compounds

  • Name the metal followed by its oxidation state in Roman numerals.
  • No Roman numerals for specific metals (e.g., Group I and II metals, Al, Zn, Cd, Ag).
  • Nonmetals are named with an “ide” ending.

Polyatomic Ions

  • Cations: NH4+
  • Anions: Include acetate (CH3COO−), sulfate (SO42−), carbonate (CO32−), hydroxide (HO−), nitrate (NO3−), phosphate (PO43−), permanganate (MnO4−).

Naming Molecular Compounds

  • Use numerical prefixes to denote the number of atoms (e.g., Mono, Di, Tri).
  • Name the first element followed by the second with an “ide” ending.

Naming Acids

  • Binary acids: Start with "hydro-" plus the second element's name ending in “ic acid” (e.g., HF - Hydrofluoric acid).
  • Oxyacids: Named based on the number of oxygen atoms present relative to a root element:
    • Hypo-: Fewest oxygen atoms.
    • -ous: One fewer than the most.
    • -ic: Most oxygen atoms.
    • Per-: One more than the most.

Strong Acids to Memorize

  • Binary Acids: HCl, HBr, HI.
  • Oxyacids: HClO3, HClO4, HNO3, H2SO4.

SI Units

  • Common SI units include:
    • Length: Meter (m)
    • Time: Second (s)
    • Temperature: Kelvin (K)
    • Mass: Kilogram (kg)
    • Mole: Amount of substance (mol)
    • Electric current: Ampere (A)

Unit Prefixes

  • Common prefixes:
    • Tera (10^12), Giga (10^9), Mega (10^6), Kilo (10^3), Centi (10^-2), Milli (10^-3), Micro (10^-6), Nano (10^-9).

Dimensional Analysis Steps

  • Write down the value you want to convert.
  • Create parentheses for the conversion factors.
  • Ensure units in the numerator and denominator cancel appropriately.
  • Multiply out and simplify to achieve the desired units with appropriate significant figures.

Example Conversion

  • To convert 8.41 × 10^6 L to gallons:
    • Set up the conversion factors with L in the denominator and gal in the numerator.
    • Use the known relationship 1 gal = 3.785 L to fill in numbers.
    • Calculate to find the volume in gallons.### Unit Conversion and Calculations
  • Ensure parentheses are correctly used in calculations to achieve a true statement.
  • When multiplying units, cancel out starting units to reach desired ones.
  • Significant figures must be applied in results, especially when calculations are done without a calculator.

Density and Conversion

  • Density is defined as mass divided by volume, crucial for converting between mass and volume.

Time and Distance Questions

  • Know conversions for time: seconds in a day (86,400 sec), hours in a year (approximately 8,760 hr).
  • Understand mass conversions: 1 kg = 1,000,000 µg, and conversions between miles and kilometers (1 mile = 1.61 km).
  • Be able to convert between different units of distance, such as kilometers to centimeters (1 km = 100,000 cm).

Significant Figures

  • Significant figures indicate the precision of measurements; count from the first non-zero digit.
  • Rules for significant figures:
    • Zeroes between non-zero digits are significant (e.g., 1005 kg has four figures).
    • Leading zeroes (e.g., 0.02 g) are not significant.
    • Trailing zeroes are significant only if there is a decimal point (e.g., 0.0200 g has three figures).

Arithmetic with Significant Figures

  • For addition/subtraction, the result should match the decimal places of the least precise measurement.
  • For multiplication/division, the result should match the smallest number of significant figures among the values.

Precision vs. Accuracy

  • Precision relates to the closeness of repeated measurements.
  • Accuracy represents how close a measurement is to the actual value.

Percent Error

  • Percent error compares the theoretical value to the actual measure and is expressed as:
    • % error = ((actual - theoretical) / theoretical) × 100

Lab Safety

  • Wear personal protective equipment (PPE) in the lab including lab coats, goggles, and gloves.
  • Common sense should guide safety practices, avoiding risky behaviors.

Test Tube Heating

  • Use appropriate holders to heat test tubes safely; avoid open flames when possible.
  • Always add acid to water for dilution to prevent exothermic reactions causing spattering.

Weighing Reagents

  • Always weigh reagents on weigh paper; tare the paper first for accurate measurements.
  • Avoid contamination by not transferring reagents directly from containers into weigh paper.

Measuring Liquids

  • Read liquid volumes at the bottom of the meniscus in graduated cylinders.
  • Parallax errors occur if the measurement is viewed from an incorrect angle.

pH Meter Usage

  • Calibrate the pH probe with standard buffers before use.
  • Rinse and dry the probe between samples for accurate measurements.

Introduction

  • Investigates levels of microbial contaminants in various makeup products.
  • Research question: Assess microbial contamination in lipstick, lip gloss, eyeliners, mascaras, and beauty blenders, and associated health risks.
  • Main arguments: Dropping products, using unsanitary or expired items elevates contamination risks in makeup.

Materials and Methods

  • Analyzed 100 microliters from each makeup product type, inoculated on various media: NA, MSA, SMAC, SAB, VRBGA.
  • Emphasized accurate measurements for product quantities and inoculation procedures.
  • Two tables and two figures utilized to support data presentation and methodology.

Results

  • Beauty blenders showed the highest level of microbial contamination among tested products.
  • Significant microbial growth detected across all tested makeup products, presenting potential health risks.
  • Results were illustrated through tables and figures, complemented by detailed explanations in the results and discussion sections.
  • Figure captions clarified the comparison and information displayed, while table captions provided brief explanations of table contents.

Discussion

  • Discussed specific bacterial types identified in contaminated makeup and related health concerns.
  • Suggested prevention methods to mitigate contamination: avoiding makeup testers and not sharing products.
  • Findings validated the initial hypothesis regarding contamination levels.
  • Cited previous research connecting bacteria types and the importance of prior studies on makeup contamination reduction.
  • Reiterated main findings and their implications on public health, reinforcing the need for consumer awareness regarding makeup safety practices.

Bacterial Species and Their Impact

  • A small percentage of bacteria cause clinical diseases in humans.
  • Bacteria play crucial roles in bioremediation, nutrient cycling, and producing substances like insulin.
  • "Germs" is a common term that oversimplifies the diversity of microorganisms.

Microorganisms and Their Classification

  • Microorganisms display various traits, such as morphology and movement, similar to human differences.
  • Representative members of Eukarya and Bacteria will be studied, along with nonliving viruses.
  • Understanding morphology and arrangements is essential for microbial identification.

Types of Bacterial Morphologies

  • Bacteria typically exhibit three shapes: coccus (circular), bacillus (rod), and spirillum (spiral).
  • Arrangement examples:
    • Streptococcus pyogenes: chain-like (coccus).
    • Staphylococcus aureus: grape-like clusters (coccus).

Microscopy Basics

  • Observing microorganisms requires a microscope due to their small size.
  • A bright light microscope uses visible light, with multiple objective lenses for varying magnification.
  • Monocular microscope has one eyepiece; binocular microscope has two.

Operable Components of a Microscope

  • Light passes from the base through a condenser onto the specimen held on a mechanical stage.
  • An iris diaphragm controls light intensity; four objective lenses magnify the specimen at different levels (4X, 10X, 40X, and 100X).
  • The 100X objective requires oil immersion to enhance clarity due to light refraction.

Understanding Resolution and Magnification

  • Resolution is the ability to distinguish between two objects; optimal is approximately 0.2 μm with bright light microscopes.
  • Electron microscopes provide higher resolution due to shorter electron wavelengths, surpassing light microscope limitations.

Specialized Microscopy Techniques

  • Dark-field microscopy allows visualization of unstained living specimens against a dark background.
  • Phase-contrast microscopy enhances visibility of cellular organelles and motility in living specimens.
  • Fluorescence microscopy uses fluorochrome dyes to detect specific microorganisms by glowing under ultraviolet light.

Electron Microscopy Types

  • Transmission Electron Microscope (TEM): Visualizes internal structures by directing electrons through the specimen.
  • Scanning Electron Microscope (SEM): Highlights surface details using scattered electrons.

Microscope Care and Handling

  • Always transport microscopes with care; support both the arm and base and keep it close to the body.
  • Clean lenses before use with lens paper and 70% ethanol to maintain efficiency.
  • Observing slides should involve both eyes open to reduce eye strain.

Post-Use Procedures

  • After completing lab work, remove slides, clean lenses, and return the microscope to its designated position.
  • Properly store the microscope with the arm facing forward in the cabinet to ensure safety and longevity.

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Description

This quiz offers a quick review of fundamental chemistry concepts, focusing on atoms, ions, and molecules. Explore the characteristics of these particles, how ions are formed, and their significance in chemical reactions.

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