skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Undergraduate Chemistry Students’ Conceptualization of Models in General Chemistry
Award ID(s):
1611622
PAR ID:
10131606
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Journal of Chemical Education
Volume:
96
Issue:
3
ISSN:
0021-9584
Page Range / eLocation ID:
455 to 468
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
  2. Abstract. In this paper, we present a new version of the chemistry–climate model SOCOL-AERv2 supplemented by an iodine chemistry module. We perform three 20-year ensemble experiments to assess the validity of the modeled iodine and to quantify the effects of iodine on ozone. The iodine distributions obtained with SOCOL-AERv2-I agree well with AMAX-DOAS observations and with CAM-chem model simulations. For the present-day atmosphere, the model suggests that the iodine-induced chemistry leads to a 3 %–4 % reduction in the ozone column, which is greatest at high latitudes. The model indicates the strongest influence of iodine in the lower stratosphere with 30 ppbv less ozone at low latitudes and up to 100 ppbv less at high latitudes. In the troposphere, the account of the iodine chemistry reduces the tropospheric ozone concentration by 5 %–10 % depending on geographical location. In the lower troposphere, 75 % of the modeled ozone reduction originates from inorganic sources of iodine, 25 % from organic sources of iodine. At 50 hPa, the results show that the impacts of iodine from both sources are comparable. Finally, we determine the sensitivity of ozone to iodine by applying a 2-fold increase in iodine emissions, as it might be representative for iodine by the end of this century. This reduces the ozone column globally by an additional 1.5 %–2.5 %. Our results demonstrate the sensitivity of atmospheric ozone to iodine chemistry for present and future conditions, but uncertainties remain high due to the paucity of observational data of iodine species. 
    more » « less
  3. Abstract Students in a second semester general chemistry course used quantum chemical calculations to investigate and reinforce general chemistry concepts. Students explored the isomers of hypochlorous acid, made predictions of miscibility via dipole moments calculated from ab-initio means, experimentally validated/disqualified their miscibility predictions, and used molecular models to visualize intermolecular attraction forces between various compounds. Student responses in pre-/post-exercise assessments show evidence of student learning. Responses in pre-/post-exercise surveys showed an increase in student understanding of basic concepts and of the importance of quantum mechanics in common general chemistry topics. 
    more » « less
  4. Environmental chambers have been playing a vital role in atmospheric chemistry research for seven decades. In last decade, oxidation flow reactors (OFR) have emerged as a promising alternative to chambers to study complex multigenerational chemistry. OFR can generate higher-than-ambient concentrations of oxidants via H 2 O, O 2 and O 3 photolysis by low-pressure-Hg-lamp emissions and reach hours to days of equivalent photochemical aging in just minutes of real time. The use of OFR for volatile-organic-compound (VOC) oxidation and secondary-organic-aerosol formation has grown very rapidly recently. However, the lack of detailed understanding of OFR photochemistry left room for speculation that OFR chemistry may be generally irrelevant to the troposphere, since its initial oxidant generation is similar to stratosphere. Recently, a series of studies have been conducted to address important open questions on OFR chemistry and to guide experimental design and interpretation. In this Review, we present a comprehensive picture connecting the chemistries of hydroxyl (OH) and hydroperoxy radicals, oxidized nitrogen species and organic peroxy radicals (RO 2 ) in OFR. Potential lack of tropospheric relevance associated with these chemistries, as well as the physical conditions resulting in it will also be reviewed. When atmospheric oxidation is dominated by OH, OFR conditions can often be similar to ambient conditions, as OH dominates against undesired non-OH effects. One key reason for tropospherically-irrelevant/undesired VOC fate is that under some conditions, OH is drastically reduced while non-tropospheric/undesired VOC reactants are not. The most frequent problems are running experiments with too high precursor concentrations, too high UV and/or too low humidity. On other hand, another cause of deviation from ambient chemistry in OFR is that some tropospherically-relevant non-OH chemistry ( e.g. VOC photolysis in UVA and UVB) is not sufficiently represented under some conditions. In addition, the fate of RO 2 produced from VOC oxidation can be kept relevant to the troposphere. However, in some cases RO 2 lifetime can be too short for atmospherically-relevant RO 2 chemistry, including its isomerization. OFR applications using only photolysis of injected O 3 to generate OH are less preferable than those using both 185 and 254 nm photons (without O 3 injection) for several reasons. When a relatively low equivalent photochemical age (<∼1 d) and high NO are needed, OH and NO generation by organic-nitrite photolysis in the UVA range is preferable. We also discuss how to achieve the atmospheric relevance for different purposes in OFR experimental planning. 
    more » « less