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Hands-on activities and supplies for
K-8 science education.
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Viscosity in Liquids

Description: Measure the drop time of a marble in various liquids to determine thickness/viscosity.

Grades:
5th-8th

Objectives/Standards:
1.Understand that all liquids flow to fill the space in which they are contained.
2.Understand that liquids flow at different rates.
3.Viscosity is a liquid's resistance to flow, or its stickiness or thickness.

Materials:
1.) 5-10 different liquids such as cooking oil, milk, heavy cream, water, syrup, apple juice, glycerin, hand sanitizer or aloe vera gel.
2.) 5-10 clear liquid containers such as jelly jars to hold liquids.
3.) 5-10 marbles in similar sizes.
4.) Stop watch or seconds timer
5.) Paper, pen or pencil

Procedure:
1.) Label paper with the name of each liquid, each liquid's height (in the jar) in centimeters, and a space to record the marble drop times.
2.) Fill the clear containers to the same height with each liquid.
3.) Place them against a white or solid background for clear viewing. 
4.) Using a timer, record the time it takes for a marble to fall through the liquid in each jar. Be careful to start and stop the timer when the marble is at the top and bottom of each liquid.
5.) Repeat step (4.) twice and calculate the average drop time for each liquid. The average drop time is found by adding together a liquid's drop times and dividing by that liquid's number of drop times. (three).
6. Record the average drop time for each liquid.
7. Rank the liquids in order of drop times. Which liquid gave the most resistance to flow or slow the marble down the most (had the greatest drop time)? This liquid is the most viscous.

Explanation:
Liquids form the shape of their containers because the molecules that make up liquids flow past each other in loosely held forces of attraction. Solids are held or bonded together more tightly and therfore hold their shape independently. Viscosity is a measure of how tightly a liquid is held together or a liquid's resistance to flow. A highly viscous liquid is one that flows slowly or is thick like syrup. It is much harder to push things through a viscous fluid because the molecules in the fluid are chemically bonded together more tightly than other liquids.

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