How does adding salt to water affect its surface tension?
Research: Water has a stronger surface tension than most liquids. It is a polar molecule which means it has partial negative and partial positive ends creating hydrogen bonding. This makes an attraction between water’s molecules called cohesion, which is why water beads up on many surfaces, like car windows. The polarity of water also attracts itself to all kinds of other substances and surfaces. This is called adhesion.
Salt’s charged ions upset water molecule’s hydrogen bonding. – chemistrystackexchange.com
Hypothesis: I predict if salt interrupts the water’s molecular attraction, salted water will have a lower surface tension.
Procedure: Independent Variable- plain tap water, tap water with salt added Dependent Variable- amount of drops and water each coin holds
Controls- same face and size of coins used, same dropper used
I first filled two bowls with plain tap water then poured two tablespoons of salt into one bowl and stirred until it was mixed in thoroughly. Then placed two quarters, each heads side up, on a flat desk. Using a dropper I filled it with the plain water and carefully squeezed drops onto one quarter, bringing it as close as I could to it without touching until the quarter filled up and spilled over. Then doing the same for the salt water with the other quarter. I replicated this three times for each quarter, rinsing out the dropper of any salt left over and drying the quarters every new time. For every time it was repeated the amount of drops that fit on the side of the quarter before spilling over never varied by more than three.
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Amount of Plain Water Drops Before Spilling Over
Amount of Salt Water Drops