The study sought to find out the relative effect of curriculum and item-teaching techniques on students’ conceptual understanding in heat and vapours in senior secondary school in Zamfara State. Three research questions and three null hypotheses guided the study. The study adopted a quasi-experimental research design, precisely non-equivalent control group design. Simple random and Purposive sampling techniques were used to select a sample of 157 SS2 physics students for the study. Thermal Conceptual and Traditional Physics Exercises (TCTPE), which has twenty (20) items, was used to collect data for the study. Three experts in Department of Science Education, University of Nigeria, Nsukka, validated the instrument. Two reliability estimates confirmed the reliability of the instrument (TCTPE). The first tested the temporal stability and the second, the internal consistency of the TCTPE. The estimated values of 0.76 and 0.82 were obtained. The data obtained for the study were analyzed using frequencies, percentages, mean and standard deviation. Also, Analysis of covariance (ANCOVA) and Chi-square were used to test the null hypotheses at 0.05 level of significance. Findings of the study revealed that item-teaching technique increase students’ achievement (or test) score in Traditional Physics Exercises in Heat and Vapour. However, there is no statistically significant difference in the mean achievement score of students given traditional physics exercises in heat and vapours under curriculum and item-teaching techniques. Meanwhile, students under curriculum teaching techniques had higher Conceptual Understanding mean score in heat and vapours, compared to their counterpart under item-teaching techniques. Finally, it was revealed that majority of students under curriculum teaching techniques were on scientific/conceptual understanding level, compared to their counterpart under item-teaching techniques where a very small number of students were on Scientific/Conceptual Understanding level. The study therefore, recommends that Physics teachers should teach to the curriculum for scientific/conceptual understanding of Senior Secondary School Students.