基于项目学习的高中化学教学设计与实践*——以“探究食品脱氧剂中的化学问题”为例

以“探究食品脱氧剂中的化学问题”为项目学习主题,以探究食品脱氧剂的主要成分、脱氧原理、能量转化形式为项目学习活动,呈现了基于项目学习的高中化学教学设计思路、教学流程,进行了项目教学实施,并结合前后测、学生自评互评和教师评价量表从知识、能力、素养等方面分析了实施项目教学后的效果。     

鲁西北地区高中化学教师有效教学行为的调查与分析

通过对鲁西北地区高中化学教师有效教学行为的调查,揭示了高中化学教师不同教学行为有效性的差异、化学教师教学行为之不同形式的有效性及差异.调查发现高中化学教师化学演示行为、化学实验教学行为以及多样化教学行为有效性较低.为提高化学教师教学方面的有效性,笔者认为在高中化学教师培训工作中应重视实践知识的培训、吸取更多一线化学教师投入到化学实验教学资源的开发利用上来以改革化学演示实验,并增强化学探究实验的可行性.     

高中化学课程中实验探究水平和探究技能的分析

运用内容分析法,分析高中化学教科书、山东省高中化学实验报告册和山东省高考化学实验试题中实验探究水平和探究技能。高中化学教科书中的实验以证实性和结构性水平为主,高中化学实验报告册中的实验为结构性水平,山东省高考化学实验试题具有指导性探究水平。3者在设计实验方案探究技能方面,出现不均衡性,较少出现提出问题、实验目的、实验假设等技能,但是,都重视分析证据得出结论和科学解释的探究技能。     

高中化学“次氯酸盐的性质”的项目式教学*——84消毒液的使用指南

以“84消毒液的使用指南”为主题,开展高中化学“次氯酸盐的性质”的教学。学生通过完成“一张图说清消毒剂”“探究84消毒液的漂白效果与酸碱性的关系”“探究84消毒液的漂白效果与光照的关系”“探究84消毒液的漂白效果与温度的关系”“84消毒液与酒精混合会有氯气吗”等5个项目任务,理解了次氯酸盐的性质及漂白原理,培养了学生的文献检索能力、实验探究能力以及发展了学生的高阶思维能力。将文献查阅与学生实验相结合,让学生在真实问题的解决中,完成次氯酸盐的性质等相关知识的内化,是顺利完成本项目教学的关键。     

以拓展课为载体将化学从课内延伸到课外——“乙酸乙酯”的教学案例

在新课改背景下,利用拓展课将基础型课程进行拓展和延伸,以满足学生不同程度的求学需求。以现代分析仪器——气相色谱仪为检测手段、课内与课外相结合的探究模式,设计了探究合成乙酸乙酯平衡移动的一则拓展课教学案例。该思路有助于探索中学化学课堂"基本实验—系列实验—设计性实验"阶梯式教学的模式,与基础课程形成互补之势,在时间和空间上扩大化学教学的领域,切实地提高化学教学效率。     

利用预测和实验的冲突促进探究学习——“原电池的工作原理”课例分析

实验在化学教学中起着重要的作用,实验探究是实验教学的重要手段.高中化学课堂中出现预设和实验冲突的现象,应该培养学生实事求是的学风、严肃认真的科学态度以及探讨问题的科学方法,帮助学生理解和运用化学基本概念、化学定律和化学原理.     

在“过氧化钠与水反应”定量实验探究中提升核心素养*

以高中化学中“过氧化钠与水的反应”的定量化实验探究过程为例,针对反应后滴入酚酞时溶液立即变深红色,随后颜色逐渐变浅甚至褪色的反常现象,通过控制变量,多角度探析了反应历程。凸显定量化的实验活动在提升学生实验探究与创新意识、证据推理与模型认知等化学核心素养中的重要作用;归纳了元素化合物模块的实验教学活动的一般思路;更好地说明化学是一门以实验为基础的科学。     

基于项目式学习的数码比色法测量紫外线强度实验设计

基于项目式学习的理念，设计了“数码比色法测量紫外线强度”拓展实验。利用紫外线催化反应制作紫外线光敏试纸；改变光敏试纸的曝光时长，制作标准比色卡。利用数码成像法，测量标准比色卡的R值和吸光度，绘制标准曲线。最终用这种测量方法比较了SPF50防晒霜、SPF20防晒霜、防晒衣、遮阳伞、身体乳、凡士林等的防晒效果。本实验具有任务驱动、开放程度高、跨学科整合、成果物化等特征。     

STSE教育和“做科学”共赢的化学实验探究模式——评美国《社会中的化学》中的“物质的探究”

美国高中化学教材《社会中的化学》中设置了大量的“物质的探究”活动。每个探究活动都强调实验基本原理的教学,实验过程的设计独具匠心,重视学生“做中学”。“物质的探究”不仅反映了化学、技术、社会、环境紧密联系的课程理念,而且体现了化学实验方法教育的多种重要价值。     

“实验化学”模块教学策略初探

“实验化学”是高中化学课程的一个重要模块,教师应在教学中既注重学生实验基础知识的巩固,也要注意培养学生的实验设计能力、术语表达能力、探究精神和合作精神。     

Sunscreen isn't enough.

Topical sunscreens act by absorbing or scattering UV radiation and are widely available for general public use as a consumer product. Surveys carried out in the UK find that sunscreen use is regarded as the most important, and by implication the most effective, sun protection measure. But is perception borne out by reality? Sunscreens applied at the thickness tested by manufacturers need only possess an SPF of 15 to prevent sunburn even for all day exposure in tropical sunshine. Yet behavioural studies show that high SPF (>15) sunscreens do not always prevent sunburn. That the protection achieved is often less than that expected depends upon a number of factors: application thickness and technique; type of sunscreen applied; resistance to water immersion and sand abrasion; and when, where and how often sunscreen is re-applied. These factors provide ample evidence that the numerical measure of protection indicated on the product pack is generally higher than achieved in practice. This mismatch between expectation and realisation may be one contributing factor why sunscreens have been reported to be a risk factor in melanoma.     

一测多评方法应用于高效液相色谱法测定防晒产品中15种防晒剂的含量

选用CAPCELL PAK C18色谱柱为分离柱,柱温为30℃,进样体积为10.0μL,并用不同比例的(A)甲醇、(B)四氢呋喃和(C)0.008 2mol·L^-1高氯酸溶液的混合液作为流动相,按程序梯度洗脱模式对市售防晒产品中所用的15种防晒剂的标准品进行色谱分离,并在波长311nm处进行紫外检测。实样分析时,称取样品0.25g,用甲醇、四氢呋喃、水和高氯酸(体积比为250∶450∶300∶0.2)的混合液(以下简称混合溶剂)15 mL超声提取30 min,用混合溶剂定容至25.0mL,离心10min,分取上清液1.0mL,加入混合溶剂定容至10.0mL,经0.45μm滤膜过滤,取滤液按仪器工作条件进行高效液相色谱分析。结果表明:所测定的15种防晒剂在一定的质量浓度范围内与其对应的峰面积呈线性关系。选定其中的二苯酮-3为参照物,并根据其余14种化合物的质量浓度和峰面积计算了各化合物的相对校正因子和相对保留时间等参数,确定了用一测多评法(QAMS)测定防晒产品中15种防晒剂的条件。还对色谱柱的型号、色谱仪器的型号以及柱温、进样量等对相对校正因子和保留时间可能产生影响的因素进行了系统试验。证明了在选定的色谱柱型号的前提下,用QAMS方法可实现防晒产品中15种防晒剂含量的同时测定。应用QAMS方法测定了6个批次防晒产品中的防晒剂含量,所得结果与用标准曲线法计算的结果基本一致,表明QAMS方法在降低检测成本和节省检测时间方面效果显著。     

A Review of Sunscreen Safety and Efficacy

The use of sunscreen products has been advocated by many health care practitioners as a means to reduce skin damage produced by ultraviolet radiation (UVR) from sunlight. There is a need to better understand the efficacy and safety of sunscreen products given this ongoing campaign encouraging their use. The approach used to establish sunscreen efficacy, sun protection factor (SPF), is a useful assessment of primarily UVB (290–320 nm) filters. The SPF test, however, does not adequately assess the complete photoprotective profile of sunscreens specifically against long wavelength UVAI (340–400 nm). Moreover, to date, there is no singular, agreed upon method for evaluating UVA efficacy despite the immediate and seemingly urgent consumer need to develop sunscreen products that provide broad-spectrum UVB and UVA photoprotection. With regard to the safety of UVB and UVA filters, the current list of commonly used organic and inorganic sunscreens has favorable toxico-logical profiles based on acute, subchronic and chronic animal or human studies. Further, in most studies, sunscreens have been shown to prevent the damaging effects of UVR exposure. Thus, based on this review of currently available data, it is concluded that sunscreen ingredients or products do not pose a human health concern. Further, the regular use of appropriate broad-spectrum sunscreen products could have a significant and favorable impact on public health as part of an overall strategy to reduce UVR exposure.     

防晒剂的分类、作用机理与评价

随着科学的发展和人们健康意识的提高,紫外线对皮肤的危害已引起人们的广泛关注。炎热的夏季,越来越多的人开始使用各种防晒剂来保护自己,这促使其大量上市,前景广阔。但是,如何寻求安全、有效的防晒剂也是消费者和研究者的关注焦点。本文简要阐述了防晒剂的分类、作用机理与评价方法,并对防晒剂的进一步发展作了展望。     

Synthesis and Evaluation of Chalcone Derivatives as Novel Sunscreen Agent

Ultraviolet (UV) irradiation is a serious problem for skin health thus the interest in the research to develop sunscreen agent has been increasing. Chalcone is a promising compound to be developed as its chromophore absorbs in the UV region. Therefore, in the present work, we synthesized eight chalcone derivatives through Claisen–Schmidt condensation at room temperature. The evaluation of the optical properties of each chalcone derivatives in the UV region was conducted through spectroscopic and computational studies. The synthesized chalcones were obtained in good yields and they were active in the UV region. The results revealed that more methoxy substituents to chalcone leads toward red shift. All chalcone derivatives have high molar absorptivity value (21,000–56,000) demonstrating that they have the potential to be used as the sunscreen agent. The cytotoxicity assay showed that chalcone derivatives were demonstrating low toxicity toward normal human fibroblast cell, which is remarkable. Therefore, we concluded that the synthesized chalcones in this work were potential to be developed as novel sunscreen agents in real application.     

Laser Flash Photolysis Studies of the UVA Sunscreen Mexoryl SX

Abstract The results of a nanosecond laser flash photolysis investigation of the UVA sunscreen Mexoryl* SX in various solvent environments and within a commercial sunscreen formulation are reported. To the best of our knowledge this is the first laser flash photolysis study of a commercial suncare formulation. In each of these environments kinetic UV-visible absorption measurements following nanosecond 355 nm laser excitation reveals a short-lived species with a solvent-dependent absorption maximum around 470–500 nm and a solvent-dependent lifetime of 50–120 ns. This transient absorption is attributed to the triplet state of Mexoryl* SX on the basis that it is quenched by molecular oxygen leading to the formation of singlet oxygen in acetonitrile. The singlet oxygen quantum yield (φ_Δ), determined by comparative time-resolved near-infrared luminescence measurements and extrapolated to the limit of complete triplet state quenching, is estimated as 0.09 ± 0.03 in acetonitrile. In aqueous solution the shorter triplet state lifetime combined with lower ambient oxygen concentrations precludes significant triplet state quenching. For the commercial sunscreen formulation there was no observable difference in the measured triplet lifetime between samples exposed to oxygen or argon, suggesting that the singlet oxygen quantum yield in such environments is likely to be orders of magnitude lower than that measured in acetonitrile.     

Photoprotective Potential of Baccharis antioquensis (Asteraceae) as Natural Sunscreen

In the quest for new natural agents of photoprotection, we evaluated the photoprotective and antioxidant activity of B. antioquensis leaf extracts as well as its phenolic composition. The methanolic extract treated with activated carbon showed the highest absorption coefficients for UVA‐UVB radiation, as well as an antioxidant capacity comparable to butylated hydroxy toluene. Furthermore, the formulation containing this extract showed suitable sensorial and photostable characteristics for topical use, and significant values of UVAPF, critical wavelength (λ_c), UVA/UVB ratio and sun protection factor (5.3, 378 nm, 0.78 and 9.1 ± 0.1, respectively). In addition, three glycoside derivatives of quercetin, a kaempferol glycoside and a derivative of caffeic acid were the main polyphenolic compounds identified. These results demonstrate the potential of B. antioquensis extracts to be used as active components of novel, natural sunscreens.     

Examination of Solar Simulators Used for the Determination of Sunscreen UVA Efficacy

The U.S. FDA recently proposed both in vivo and in vitro UVA efficacy tests for sunscreen products with the lower result used to establish the sunscreen's labeled UVA protection claim. The FDA stated their rationale for dual tests was concern that the in vivo test method overemphasizes UVA-2 (320–340 nm) photoprotection. We attribute FDA's observation to the relative lack, compared to sunlight, of UVA-1 (340–400 nm) radiation in the current JCIA UVA solar simulator specification, allowing the method to generate higher UVA protection factors than sunscreens will provide in sunlight. Our work is based upon comparisons of Air Mass 1.0 sunlight to variously filtered UVA solar simulators. Sources near the JCIA UVA-2/UVA limits (8–20%) had a goodness of fit to solar UVA of only 67–79%. We propose that instead of using ratios of UVA-2 to UVA the standard should be a goodness of fit to the UVA region of an Air Mass 1 solar reference spectrum. As the spectral distribution of solar UVA varies much less than UVB, sunlight of reasonable zenith angles of ≤60° will have similar spectral shapes and approximate risk spectrum. Goodness of fit to this spectrum will produce UVA protection values predictive to those actually achieved in sunlight of different zenith angles.     

含辅酶Q10材料的抗辐射性能及含量测定

采用高效液相色谱法测定了辅酶Q10(CoQ10)的含量,并探讨了CoQ10的防晒性能.色谱柱为Kromasil 5-C18柱(150×4.6 mm,5μm);流动相为甲醇-无水乙醇(体积比30:70),流速为1.0 mL/min;检测波长275 nm.实验考察了不同含量CoQ10在3个紫外区的防晒性能,及与维生素C或维...