Question 9
A student performs an experiment to determine the melting point of an unknown
solid substance G. She takes the substance in a beaker and starts heating. She
immersed a thermometer into the beaker and noted the change in temperature
every minute. She then plotted the change in temperature of the substance against
time and obtained a graph like below:
a. What is the melting point of substance G in degrees Celsius? (1 mark)
b. Why does the temperature remain constant from 9th min to 15th min of the
experiment? (1.5 marks)
c. Using (O) to represent particles of substance G, draw at least ten particles as
they would appear at point Z. (1 mark)
d. If we allow the same sample of the same compound to cool down, draw the
resulting graph. (1.5 marks)
solid substance G. She takes the substance in a beaker and starts heating. She
immersed a thermometer into the beaker and noted the change in temperature
every minute. She then plotted the change in temperature of the substance against
time and obtained a graph like below:
a. What is the melting point of substance G in degrees Celsius? (1 mark)
b. Why does the temperature remain constant from 9th min to 15th min of the
experiment? (1.5 marks)
c. Using (O) to represent particles of substance G, draw at least ten particles as
they would appear at point Z. (1 mark)
d. If we allow the same sample of the same compound to cool down, draw the
resulting graph. (1.5 marks)