Despite its great success, the concept of competence still is neither clear nor distinct. In the French education system, the concept of competence is defined as the ability to mobilize and reinvest knowledge, skills and abilities in order to achieve a given objective in a complex situation. Focusing on the notion of competences thus allows for increased attention to learning processes, how the student learns and uses his or her knowledge, and ultimately to the cognitive functioning of individuals [1] .

Many authors [2] [3] [4] [5] [6] emphasize the dynamic nature of competence and invite refocusing on the learning processes of the student rather than on the content of instruction, on the relationship between knowledge acquisition, skills development, and the adoption of attitudes. They also emphasize the process of contextualization that subordinates the acquisition of knowledge to the mobilization of resources in new situations.

In this context, the curricula of the French education system were reformed and defined, not in terms of content, but in terms of skills that pupils should acquire during their schooling [1] . The introduction of logic of skills in the teaching of chemistry in the French education system led us to consider carefully the requirements of this method of education and training, its conditions of application and the relative limits to its implementation.

Improving the application of a pedagogical approach needs a permanent review from practisers. This paper aims to highlight the impact of the use of the skill-based approach in the learning process of chemistry. Indeed, we wanted to analyze the process of acquisition of skills by students during the learning of chemistry in 5^th grade. Therefore, we implemented a skill-based approach to identify the inputs and gaps in this method in the learning of the discipline. The objective is to show that despite the good intentions associated with the skill-based approach, its implementation does not always produce the expected effects of the program designers, and therefore requires adjustments to improve the learning framework students.

Various activities were proposed to the pupils, during which they were placed in a situation of permanent evaluation [8] , and whose level of demand is relative to the progression of learning:

1) The practical work was the main part of the activities carried out; indeed, experimental skills were combined with other types of skills, and evaluated instantaneously because experimental activity can perform only once [9] [10] ;

2) Documentary studies also contributed to the investigation, the acquisition of knowledge and the construction of skills;

3) The lessons summarized the essential notions to be learned [11] ;

4) The exercises to be carried out outside the classroom and corrected in class were used to train pupils to mobilize acquired skills;

5) Resolving scientific problems was to mobilize a set of skills and to use provided information in order to answer a research question;

6) Individual assessments evaluate skills’ acquisition.

The activities of acquiring a set of skills divided into two or three areas, depending on their nature, are practical work and documentary studies, and those which were used to reinvest them are individual assessments and problem solving. We limited the number of engaged and evaluated skills in each activity. For practical reasons (organization of laboratory equipment, small room with possibility of communication between the students), most activities were carried out by group, except for individual assessments. The teacher imposed the composition of each group in order to have a relative homogeneity, notably in terms of skills and level of performance. Indeed, each group is composed as much as possible of a student with high scientific potential, a pupil who is able to bring a useful transversal expertise during the activity and a student with shown difficulty.

Based on the defined skills in the program and their classification by area as described by IGEN [10] , we classified the evaluated skills during each activity by area in the “Analyze”, “Realize” and “Validate” areas, as it is presented in the Table 1.

The evaluation of the activities was based on skills in accordance with the program guidelines [7] . The mobilization of a skill is evaluated in relation to the other skills of the same area [8] [9] . For each group of students during the group work, and for each student during individual assessment, the proficiency level is assigned to each of the identified skills’ areas during the activity, according to 4 levels:

1) the group or the pupil demonstrated mastery of the skills in the area by performing all the requested work satisfactorily according to the specified criteria or with one or two interventions of the teacher, concerning difficulties identified and explained by pupil, and to which he answers by himself;