This study aims to produce a guided inquirybased salt hydrolysis module to improve students'
critical thinking skills by determining the level of
validity, practicality and effectiveness of the module.
The type of research used is research development or
Research and Development (R&D). The sampling
technique uses cluster purposive sampling. The number
of samples is 57 students from both schools. The
development model used is the Plomp development
model which has three stages namely the initial
investigation phase (preliminary research phase), the
prototype phase (prototyping phase) and the assessment
phase (assessment phase). The research instruments
used were interview sheets, questionnaires in the form
of validation and practicality sheets, objective questions,
and critical thinking questions. Data analysis techniques
using SPSS 16 software. The results obtained by N-gain
experimental class is higher than the control class that is
experimental class 1 and 2 have N-gain 64.65 and 59.46,
while control classes 1 and 2 have N-gain 60 , 83 and
58.6 with significant differences. Hypothesis test results
show a significant difference between the critical
thinking skills of the experimental class and the control
class, both in schools with high and low student abilities.
Keywords : modules, salt hydrolysis, guided inquiry,Critical thinking, Plomp Development