What error in the data is likely to occur if the hydrated salt is heated strongly

If the hydrated salt is overheated, it causes the anhydrous salt to decompose, causing the product to be lost as gas. The reported percentage of water loss will be too high because the gap between the initial measurement and final (which will be lower due to loss of sample) measurement will widen.

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.