64 Results
Exceptions to the Octet Rule   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
The Avogadro Constant   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Dipole Forces   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Polarity in Polyatomic Molecules   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Hybrid Orbitals   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Covalent Molecules and the Octet Rule   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Macroscopic and Microscopic Views of a Chemical Reaction   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Macroscopic Properties and Microscopic Models   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Multiple Bonds and Molecular Shapes   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
The Shapes of Molecules   
(Other (1))
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Bonding   
(Movie/Animation, Audio/Visual (7))
Reactions and demonstrations that explore the concepts of bonding.
Boiling Points of Straight-Chain Alkanes   
(Movie/Animation, Audio/Visual (7))
The boiling points of straight-chain alkanes with 5-10 carbon atoms are determined.
Boiling Points of Hexane Isomers   
(Movie/Animation, Audio/Visual (6))
The boiling points of the five isomers of hexane are determined.
Plastic Sulfur   
(Movie/Animation, Audio/Visual (5))
Yellow powdered sulfur is heated until it becomes molten and brown. At first it flows freely, but then it becomes very viscous. Upon further heating, the viscous sulfur flows freely again and ignites. The burning liquid sulfur is poured into a beaker of water. When removed from the water, the sulfur is rubbery and flexible.
Structures and Conformations   
(Movie/Animation, Audio/Visual (5))
Molecular models are used to demonstrate the conformations of alkanes and cycloalkanes.
pH of Acetic Acid Derivatives   
(Movie/Animation, Audio/Visual (3))
The pH of acetic acid, monochloro-, dichloro-, trichloro-, and trifluoroacetic acids are compared.
Paramagnetism   
(Movie/Animation, Audio/Visual (3))
The paramagnetic properties of oxygen are demonstrated using a strong magnet, and compared with diamagnetic nitrogen.
Piezoelectric Effect   
(Movie/Animation, Audio/Visual (2))
Sounds accompany the discharges of electricity. A piezoelectric crystal is connected to a light bulb. When the crystal is pressed, the light flashes.
Ring Strain   
(Movie/Animation, Audio/Visual (2))
Mixing solid iodine and cyclohexene shows little reaction but mixing iodine and alpha-pinene produces a very vigorous exothermic reaction and sublimation of solid iodine to dense iodine vapor.
Hydrophobic Effect   
(Movie/Animation, Audio/Visual (2))
Hydrophobic Effect: Octanoic acid forms a monolayer on the surface of water under certain conditions.
Relation of Structure to Boiling Point of Alkanes   
(Movie/Animation, Audio/Visual (2))
The boiling point of straight-chain alkanes and isomers of hexane are determined and molecular models of the hydrocarbons are shown.
Glyceraldehyde and the Fischer Projection   
(Movie/Animation, Audio/Visual (2))
Molecular models are used to demonstrate chirality of glyceraldehyde and drawing its Fischer Projection.
Molecular Models of Indicators   
(Interactive Simulation (1))
The article by Nicholas C. Thomas and Stephen Faulk on "Colorful Chemical Fountains" (1) reminds us that color—the colors of acid–base indicators or of metal complexes—is responsible for many of us developing an interest in chemistry. The featured molecules this month are the acid and base forms of three common indicators–phenolphthalein, methyl orange, and methyl red. These three substances display interesting structural features as the pH-induced transformation from one form to another takes place in three different ways. In the case of phenolphthalein, the lactam ring is cleaved on deprotonation to produce a carboxyl group with the concomitant removal of a proton from a phenolic group. In methyl orange, one of the nitrogen atoms is protonated in the acid form, and that proton is lost in the base form. In methyl red, a carboxylic acid function is deprotonated. There are many other interesting aspects of acid–base indicators. Since most plants and fruits contain pigments that show a color change in some pH range, it is difficult to state with any degree of certainty when these changes were first put to use in a systematic fashion. The Spanish alchemist Arnaldus de Villa Nova (Arnold of Villanova) is purported to have used litmus in the early 14th century. In general systematic use of indicators is traced to the latter half of the nineteenth century with the development of the three synthetic indicators described above. Many students will be familiar with the use of phenolphthalein to identify blood—often shown on the various forensic chemistry TV dramas by dropping some solution on a cotton swab that has been used to pick up some of the sample in question. If the swab turns red we frequently hear "It's blood". The reality of using phenolphthalein in this way is more complicated. The test is presumptive for the presence of blood, but not conclusive. It is not an acid–base reaction but rather, in the presence of hydrogen peroxide, relies on hemoglobin to catalyze the oxidation of phenolphthalein. An interesting assignment for students in a high-school or non-majors course would be to have them explore the details of this Kastle–Meyers test to see just what is involved in the correct application of the test, and what factors complicate the process. For example, would tomato juice infused with asparagus juice give a positive Kastle–Meyers test? Historically phenolphthalein was used in a variety of laxatives. Recently that usage has been discontinued due to concern about the carcinogenic nature of the substance. A review of the history of the controversy surrounding the use of phenolphthalein in laxatives would make a good research paper at the high-school level. Lastly, students with some practice building structures and performing calculations might wish to explore the structures of two other forms of phenolphthalein—one found in very acidic solutions, having an orange color, and one found in very basic solutions that is colorless.
Reactions : IDOxidationNumber (10 Variations)   
(Assessment Material (1))
What is the oxidation number of sulfur in barium sulfate (BaSO4)?
Reactions : HighOxNumber (10 Variations)   
(Assessment Material (1))
In which of the following does sulfur have the highest oxidation number?
Intermolecular_Forces__Liquids_and_Solids : OrganicBoilingPoint (11 Variations)   
(Assessment Material (1))
Which of the following organic compounds has the highest boiling point?
Intermolecular_Forces__Liquids_and_Solids : IntermolecularForces (10 Variations)   
(Assessment Material (1))
For which of the following compounds is hydrogen bonding the strongest?
Intermolecular_Forces__Liquids_and_Solids : BoilingPoint (10 Variations)   
(Assessment Material (1))
Which of the following substances has the highest boiling point?
Atoms,_Molecules_and_Ions : CompareParticles (20 Variations)   
(Assessment Material (1))
Which has the greater number of particles, 1 mol O2 or 1 mol O?
Bonding : IonicOrCovalent (10 Variations)   
(Assessment Material (1))
Match the following formulas to the correct type of bonding: ionic or covalent.
Stoichiometry : CompareParticles (20 Variations)   
(Assessment Material (1))
Which has the greater number of particles, 1 mol O2 or 1 mol O?
Biochemistry : Tertiary (16 Variations)   
(Assessment Material (1))
Which of the following is NOT true about the tertiary structure of water-soluble proteins?
Bonding : CompareBondLength (5 Variations)   
(Assessment Material (1))
Which of the following compounds has the shortest bond between nitrogen and oxygen?
Biochemistry : Secondary (15 Variations)   
(Assessment Material (1))
What secondary structure element is represented by the green sequence in the following structure of the protein calmodulin?

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Biochemistry : StructureDef (4 Variations)   
(Assessment Material (1))
What kind of structure is defined by the linear sequence of amino acids in the protein chain?
Biochemistry : Amphiphile (20 Variations)   
(Assessment Material (1))
Which of the following molecules is an amphiphile?
Organic : HsOnAlkaneBackbone (10 Variations)   
(Assessment Material (1))

The carbon skeleton for 2-methylbutane is shown below. How many hydrogens are present?

Atoms,_Molecules_and_Ions : CompFromNanoPic (9 Variations)   
(Assessment Material (1))
__________ can be represented by the nanoscale diagram below.

Which of the following is the best choice to fill in the blank?

Atoms,_Molecules_and_Ions : CalcMolarMass (8 Variations)   
(Assessment Material (1))
What is the molar mass of potassium phosphate, K3PO4?

Enter the numeric value very carefully below, rounding to one decimal place only. Do not put the units in, but think about what the units are!

Atoms,_Molecules_and_Ions : IonType (8 Variations)   
(Assessment Material (1))
Identify the following ion as monatomic or polyatomic and as an anion or a cation: Cr2O7-2
Atoms,_Molecules_and_Ions : IonicProperties (8 Variations)   
(Assessment Material (1))
Which of the following statements concerning the properties of ionic compounds is NOT correct?
Atoms,_Molecules_and_Ions : IonicFormula (10 Variations)   
(Assessment Material (1))
Which pair of ions will form a compound of formula M2X?
Atoms,_Molecules_and_Ions : BinaryMolcFromImage (8 Variations)   
(Assessment Material (1))
Which of the following binary compounds could the figure below best represent?

Atoms,_Molecules_and_Ions : AtomicRatio (10 Variations)   
(Assessment Material (1))
Which compound(s) contain the most nitrogen atoms per molecule or formula unit?
Atoms,_Molecules_and_Ions : AllotropesOfElement (4 Variations)   
(Assessment Material (1))
Which of the following is an allotrope of oxygen? (You may select more than one.)
Atoms,_Molecules_and_Ions : IonicOrMolecular (10 Variations)   
(Assessment Material (1))
Identify each of the following compounds as ionic or molecular.
Bonding : DetermineStructure (8 Variations)   
(Assessment Material (1))
H A substance is analyzed and found to contain 57.10% carbon, 4.80% hydrogen and 38.06% oxygen by weight. Its molecular weight is determined to be 126.11 g/mol. Which of the structures shown are possible structures for the substance?
Bonding : ValenceElectrons (10 Variations)   
(Assessment Material (1))
Determine the number of valence electrons for each molecule or ion and match it with the number in the pull-down list to the right of the formula.
Stoichiometry : FormulaFromComp (8 Variations)   
(Assessment Material (1))
Lactic acid is the substance that makes your muscles burn when you've been exercising hard. Lactic acid is composed of 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by weight. If it has a molar mass of 90 g/mol, what is its molecular formula?
Stoichiometry : CombustionAnalysis (10 Variations)   
(Assessment Material (1))
While working in the lab, you find a bottle of white powder labeled "analgesic compound #5". Since the original investigator neglected to record the identity of the substance, you decide to perform a combustion analysis to identify the compound. You have a 65.7 g sample that when burned produces 182 g CO2 and 51.7 g H2O. What is the formula of this compound? (The compound only consists of C,H, and O.)
Matter_and_Measurement : ClassifyMatter (8 Variations)   
(Assessment Material (1))
Which of the following descriptions best classifies aluminum foil?
Matter_and_Measurement : ThryOrHypothesis (6 Variations)   
(Assessment Material (1))
Identify each of the following statements as a theory or a hypothesis.
Matter_and_Measurement : HomoOrHeteroMix (10 Variations)   
(Assessment Material (1))
Identify the following as homogeneous or heterogeneous mixtures.
Matter_and_Measurement : ElemCompdMix (10 Variations)   
(Assessment Material (1))
Classify each of the following as an element, compound, or mixture.
Gases : RealGases (6 Variations)   
(Assessment Material (1))
Which gas in the following list will have the greatest deviation from ideal behavior at STP?
Gases : IDGasFromVelocity (8 Variations)   
(Assessment Material (1))
The following are graphs of molecular velocities versus the relative number of molecules for argon, chlorine, methane and xenon at 300K. Which graph is for argon?
Characteristics of Materials   
(Activity, Instructional Material (7), Test, Assessment Material (15))
What makes diapers absorbent? Is peanut butter stickier than syrup or jelly? Strong, stretchy, sticky, or sweet—everything around us has special properties which make them unique. See if you can identify and compare the characteristics of materials.
Your Senses   
(Activity, Instructional Material (2))
ACS Science for Kids activities that explore the chemistry behind our senses.
Food   
(Activity, Instructional Material (11))
ACS Science for Kids activities that explore the chemical properties of foods.
Bonding (34 Variations)   
()
A collection of 34 assessment questions about Bonding
Nomenclature (10 Variations)   
()
A collection of 10 assessment questions about Nomenclature
Modeling the Formation of Water   
()
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Ice, water, vapor   
()
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.
Molecular Gastronomy; Cooking in a Vacuum   
()
A section of ChemPrime, the Chemical Educations Digital Library's free General Chemistry textbook.