Multiple Choice
What is the freezing point of a solution made by dissolving 59.5 g of CaCl2 into 100 g of H2O, given that the van't Hoff factor (i) for CaCl2 is 3 and the freezing point depression constant (Kf) for water is 1.86 °C/m?
14. Solutions
Freezing Point Depression
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How can the freezing of water lead to the cracking of boulders?
A
Water expands upon freezing, exerting pressure on the boulders.
B
Water contracts upon freezing, pulling the boulders apart.
C
Water chemically reacts with the minerals in boulders, causing them to crack.
D
Water evaporates quickly when frozen, leading to cracks in boulders.
Verified step by step guidance1
Understand the physical properties of water: Water is one of the few substances that expands when it freezes. This is due to the formation of a crystalline structure that occupies more space than liquid water.
Consider the process of freezing: When water seeps into cracks in boulders and then freezes, it expands. This expansion can exert significant pressure on the surrounding rock.
Analyze the effect of expansion: The pressure from the expanding ice can cause the rock to crack or break apart. This process is known as frost wedging or freeze-thaw weathering.
Evaluate the incorrect options: Water contracting upon freezing is incorrect because water expands. Chemical reactions with minerals or rapid evaporation are not primary causes of cracking in this context.
Conclude with the correct explanation: The expansion of water upon freezing is the key factor that leads to the cracking of boulders, as it exerts pressure on the rock.
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