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JAMB UTME - Chemistry - 2013

Question 1 Report

The presence of an impurity in substance will cause the melting point to
Answer Details
The presence of an impurity in a substance will reduce its melting point. The melting point of a pure substance is a fixed temperature at which the solid and liquid phases coexist in equilibrium. However, when an impurity is added to the substance, the impurity molecules become incorporated into the crystal lattice of the substance. This incorporation of impurity molecules disrupts the regular arrangement of the substance's molecules, making it more difficult for the substance to maintain its crystal structure as the temperature increases. As a result, the melting point of the substance is lowered, and it melts at a lower temperature than the pure substance. This is why impurities are often added to substances like ice on roads to reduce their melting point and make them melt more quickly.
Read lesson note on Separation Of Mixtures And Purification Of Chemical Substances (JAMB)
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