Question

question 10 of 10 which two statements about the substances in this experiment are true? a. water has a higher surface tension than salty water. b. soapy water has a higher surface tension than plain water. c. quartz is harder than chalk. d. graphite is harder than quartz.

Explanation:

• Surface tension: Salty water has higher surface - tension than pure water due to dissolved ions strengthening intermolecular forces. Soap is a surfactant that reduces surface tension of water.
• Hardness: According to Mohs scale of mineral hardness, quartz (hardness 7) is harder than chalk (calcite in chalk has hardness 3) and graphite (hardness 1 - 2) is much softer than quartz.

Answer:

A. Water has a higher surface tension than salty water. (False)
B. Soapy water has a higher surface tension than plain water. (False)
C. Quartz is harder than chalk. (True)
D. Graphite is harder than quartz. (False)
So the true statements are C.