Hasil penelitian menunjukkan rata-rata hasil tes pemahaman siswa berdasarkan teori APOS adalah 53,33% siswa melalui tahap aksi, 33,33% siswa melalui tahap proses, 12,28% siswa melalui tahap objek, 2,85% siswa melalui tahap skema.

Jenis yaitu mixed methods dengan explanatory sequential mixed methods design. Subjek penelitian yaitu 21 siswa kelas VII-D SMP Negeri 278 Jakarta tahun ajaran 2019/2020. Pengambilan sampel penelitian menggunakan teknik non-probability sampling yaitu purposive sampling. Penelitian bertujuan untuk mendeskripsikan dan mengetahui faktor kemampuan pemahaman siswa berdasarkan teori APOS pada pokok bahasan suhu dan kalor.

Keywords:Difficulty, Problem Solving, Temperature and Heat

The purpose of this study is to determine the type of difficulty, causal factors, and provide solutions to overcome the difficulties in solving materials physics matter temperature and heat.Techniques of collecting data using tests, questionnaires, and interviews.The subjects of class X High School Ar-Risalah Lubuklinggau.From the analysis of the test data found the difficulty proportion of 80.3% problem, the difficulty of using symbols 76.2%, difficulty using the formula of 84%, difficulty analyzing the graph of 65% and 90% difficulty count.Based on the results of interviews and questionnaires, the factors that cause students to have difficulty understanding the problem is that students do not understand the purpose and purpose of the problem, the lack of students' understanding of the material, the students rarely repeat the material that has been studied at home and students lazy exercise to do the question.The cause of the difficulty of using symbols is that students forget the physical symbol and students remember the symbol by memorizing not understanding it.The cause of difficulty using the formula is the students are not interested and feel complicated with the matter that there is a formula and students do not master the concept of the material well.The cause of the difficulty of analyzing the graph is the students do not understand the purpose of the graph, the students feel complicated and not interested in the matter of the graph.The cause of the difficulty of counting is the students are less interested in the matter of the count, the students are not careful in calculating, the students have difficulty performing the count operation, and the teacher rarely gives a varied problem.

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