Title	: RATES OF REACTION IV

Aim	: To observe the effect of concentration on the rate of reaction .

Apparatus : 
hydrochloric acid , sodium thiosulphate , water , 250 ml beaker , 2 measuring cylinders stop watch , filter paper , marker

Directions :
Mark a cross X on the filter paper .
Measure out 40 ml of thiosulphate into the beaker and place it on the filter paper above the cross . Add 20 ml of the acid . Immediately start the watch . ( Use separate measuring cylinders ) . Looking from above time how long it takes to completely obscure the cross . Rinse the beaker and repeat with 40 ml of the thiosulphate and the following volumes :
2) 20ml acid + 10 ml water
3) 20ml acid + 20 ml water
4) 20ml acid + 30 ml water
5) 20ml acid + 60 ml water

Questions  : 
Draw a graph of the results .
What property are you measuring ?
What variable is changing which allows you to measure this property ?
How does the concentration affect the rate of the reaction ?
Is there another method that could be used to determine the effect of the 
concentration on the rate ?
If you plot a graph of conc. vs. 1/time what would that determine ?


Criteria    : ANALYSIS AND INTERPRETATION

Analysis and Interpretation

Explanations - 	5 mks
Conclusion - 	2 mks
Graph - 		3 mks