(2) (ii) Calculate the percentage change in mass for the 10 lugworms in the salt solution with a concentration of 2.0 arbitrary units. ______________________________________________________________ ______________________________________________________________ Percentage change in mass = ______________________ %

(b) The table below shows the scientists’ results.Concentration of salt in arbitrary units Mass of 10 lugworms at start in grams Mass of 10 lugworms after 8 hours in grams Change in mass in grams Percentage (%) change in mass 1.041.2 61.8 +20.6+50 2.037.5 45.0 +7.53.055.0 56.1 +1.1+2 4.046.2 22.2 -24.0-52 5.045.3 22.6 -22.7-50 (i) The scientists calculated the percentage change in mass at each salt concentration. Why is the percentage change in mass more useful than just the change in mass in grams? Use information from the table in your answer. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (2) (ii) Calculate the percentage change in mass for the 10 lugworms in the salt solution with a concentration of 2.0 arbitrary units. ______________________________________________________________ ______________________________________________________________ Percentage change in mass = ______________________ % (2)

he lugworm lives in a U-shaped burrow in the sand on the seashore. The diagram below shows a lugworm in its burrow. 4.Page 8 of 18carbon dioxide280 * 0.25 = 70m^270more Surface area means higher surface area to volume ratio which increases the rate of diffusion allowing for more gas exchange meaning more oxygen can be absorbed by the blood which helps the athlete to perform aerobic resperation(a) Some scientists investigated the effect of different salt concentrations on lugworms. The scientists: • collected 50 lugworms from the seashore • separated them into five groups of 10 lugworms • weighed each group of 10 lugworms • placed each group into a different concentration of salt solution and left them for 8 hours • took each lugworm out of the solution and placed it on blotting paper for 30 seconds • re-weighed each group of 10 lugworms. (i) Why did the scientists use groups of 10 lugworms and not just 1 lugworm at each concentration? ______________________________________________________________ ______________________________________________________________ (1) (ii) Suggest why the scientists placed each lugworm on blotting paper for 30 seconds before they reweighed the groups of lugworms. ______________________________________________________________ ______________________________________________________________ (1) (iii) How might the method of blotting have caused errors in the results? ______________________________________________________________ ______________________________________________________________ (1) (iv) Suggest one improvement the scientists could make to their investigation. ______________________________________________________________ (1)

During an osmosis experiment to determine the movement of water, students are attempting to determine the percent change in the mass of a carrot after it has been placed in a solution with sucrose for 24 hours.Fresh Chopped Carrot by ivabalk (CC0)If the starting mass of the carrot was 3.2 grams3.2 grams and the ending mass was 2.6 grams2.6 grams, what was the percent change in mass?Elimination ToolSelect one answerA−23.1%−23.1%B19%19%C−18.75%−18.75%D−0.1875%

A solution contains 10% salt and remaining is water. If 30𝓁𝑙 of water is evaporated, then salt becomes 15% find the initial solution.60𝓁𝑙105𝓁𝑙120𝓁𝑙90𝓁

In a tank 100 liters of brine solution containing 50 kg of total dissolved salt. Pure water is allowed to run into the tank at the rate of 3 L/min and brine solution runs out at the rate of 2 L/min. The solution is kept stirred to make the concentration uniform. Compute the kg of salt in the tank after 1.0 hour.Question 6Select one:A.13.59 kgB.19.35 kgC.19.53 kgD.15.93 kg