Question

a student recorded the mass of dry raisins as 3g and the mass of raisins after soaking in wateras4.8g. calculate the percentage of water absorbed by raisins. write one precautions of thus experiments

Answer 1

mass of dry raisins = 3g
mass of raisins after soaking = 4.8g
mass of water absorbed = 4.8 - 3 = 1.8 g
% of water absorbed = (1.8/3)*100 = 60%

Precaution:
Keep the raisins inside the water, not on surface

Answer 2

initial mass =  3.0 gm 
final = 4.8 gm            =>  percentage change  = (4.8 - 3)/ 3  * 100 = 60%

Precautions: 
 1.  Have sufficient water for all the raisins to absorb water.
 2. wipe out the water dripping from raisins when you take them out of water.

 3.  Keep the raisins for long time sufficient for them to absorb water completely as much as they can.
4,  See that the temperature is recorded at the beginning, during and end of the experiment.  Changes in temperature can alter the values a little.

5. have all raisins immersed completely and they are not too closely packed that water cannot penetrate between them.
6.  If there is any label or paper that is stuck on the raisins, remove them..