The student provides a focused and detailed description of the main topic, clearly explaining the investigation to obtain and compare the percentage of CaCO3 in chalk, seashells, and rangoli powder through methods of back titration and thermal decomposition. The student also presents a relevant and concise background information, although more details on thermal decomposition, back titration, and the properties of calcium carbonate could have been included. The chemistry of the experiment is explained well enough for the reader to understand it without the need for rereading. The methodology of the investigation is highly appropriate to the topic, using thermal decomposition and back titration independently to obtain the mass of calcium carbonate in the different samples. However, the student does not correctly identify the independent and dependent variables, and there is no consideration for ethical concerns.
