Some types of water contain dissolved substances. A student investigated the mass of dissolved solids in distilled water and in sea water. Figure 1 shows the apparatus. Figure 1 This is the method used. 1. Weigh an evaporating basin. 2. Add 20 cm 3of distilled water to the evaporating basin. 3. Weigh the evaporating basin and the water sample. 4. Heat the water sample for 2 minutes. 5. Weigh the evaporating basin and contents. 6. Repeat steps 1 to 5 two more times. 7. Repeat steps 1 to 6 with sea water. 0 4 . 1 The method used by the student did not give valid results. Describe one improvement the student could make to obtain valid results.
Question
Some types of water contain dissolved substances. A student investigated the mass of dissolved solids in distilled water and in sea water. Figure 1 shows the apparatus. Figure 1 This is the method used. 1. Weigh an evaporating basin. 2. Add 20 cm 3of distilled water to the evaporating basin. 3. Weigh the evaporating basin and the water sample. 4. Heat the water sample for 2 minutes. 5. Weigh the evaporating basin and contents. 6. Repeat steps 1 to 5 two more times. 7. Repeat steps 1 to 6 with sea water. 0 4 . 1 The method used by the student did not give valid results. Describe one improvement the student could make to obtain valid results.
Solution
One improvement the student could make to obtain valid results is to ensure that all the water has completely evaporated before weighing the evaporating basin and its contents. This can be achieved by heating the water sample until no more liquid is visible and then allowing the basin to cool to room temperature before weighing. Additionally, the student should use a more precise balance to measure the mass of the evaporating basin and its contents to reduce measurement errors.
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