Over 1.7 billion students around the world have had their education disrupted by the spread of the Coronavirus disease worldwide. Schools and universities have not faced this level of disruption since World War II. The COVID-19 pandemic presented a colossal challenge for teachers to urgently and massively adapt all their classes to distance learning in order to maintain educational continuity with the same quality. Even if some teachers and certain classes were ready to face the situation, a large majority had to adapt their teaching and learning in a very short time without training, with insufficient bandwidth, and with little preparation. This unexpected and rapid transition to online learning has led to a multiplication of teachers' strategies for distance learning in lectures, tutorials, project groups, lab works, and assessments. The purpose of this paper is to present the feedback from students and teachers who participated in the lockdown semester of two different groups of a 5-year program in Chemistry, Environment and Chemical Engineering (100 students) at INSA Toulouse (France). The analysis has highlighted some great successes and some failures in the solutions proposed. Consequently, some guidelines can be given to help us all to learn the lessons of such a singular experience in order to face the unexpected future with more knowledge and more successful distance learning. Teachers have shown very strong resilience during this crisis, at the cost of significant personal commitment. They admit that they have learned more about distance education in two months than in the last 10 years.

Ion hydration phenomena are of great interest in the fields of physics, chemistry, biology, geochemistry and environment. However, few studies using identical calculation methods to characterize the hydration properties of ions in water and in electrolytic systems are available. Hence, it is difficult to compare the hydration properties of ions when they come from different methods. The objective of this work is, therefore, to use a unique approach to compare the hydration properties of ions in pure water and in presence of counter-ion using a quantum mechanical method, the Density Functional Theory (DFT). For this purpose, a methodology based on the decomposition of the system's energy is described and implemented in this study. In the first part, quantum mechanics calculations are used to determine the hydration properties of ions, without counter-ion, in presence of water molecules. In the second part, the hydration characteristics of solutes in systems containing ions, counter-ions and water molecules are studied. Results show that the presence of an anion (Cl − or SO 4 2−) does not cause structural and energetic changes in the cation first hydration layer (Li + , Na + , K + , Mg 2+ , Ca 2+). Conversely, the anion first hydration layer depends on the cation of the system.