<![CDATA[Problem solving is one of the abilities that students must have in the 21st century. This is because students' ability to solve problems is expected to increase their higher order thinking skills (HOTS) competency. The ability to measure problem solving can be assessed through test instruments in the form of questions containing problems. This research aims to analyze problem solving abilities in colloidal materials through the development of the IDEAL Problem Solving assessment instrument. This instrument includes five indicators, namely Identify the Problem, Define the Outcome, Explore Possible Strategies, Anticipate Outcome & Act, and Look back and Learn. The research was conducted for 3 months at SMAN 1 Sungai Tabuk class XI semester II (even). The method used is development research or R&D (Research and Development) research. The development of this instrument adapts the ADDIE development model by following five steps, including (1) Analyze (analysis), (2) Design (planning), (3) Develop (development), (4) Implementation (implementation), (5) Evaluate (evaluation). Data analysis was conducted quantitatively with statistical tests. The results of empirical validity indicate that the instrument is valid and reliable for use and meets the criteria of good difficulty level and discrimination power. Implementation of the instrument on 25 high school students in grade XI showed an uneven distribution of scores, with most students only mastering questions with a low level of difficulty. Only a few students managed to answer questions with a high level of difficulty. This phenomenon reflects a gap in mastery of the material, which is influenced by the level of difficulty of the questions, student understanding, and factors such as learning strategies, concentration, and student confidence.]]>
