Soap Bubble Experiment

The Effect of Temperature and Atmospheric Conditions on the Life Span of a Soap Bubble

Madison Peña

Honors Foundations

Mr. King

Period C

Grade 9

February 3rd, 2015

Experimental Purpose:

The purpose of this experiment was to determine if there was variation in the life span of soap bubbles under differing temperature and atmospheric conditions which include a hot, humid environment and a cold, dry environment. This experiment was categorised in physical science, but more specifically physics and chemical science because mechanics, heat, and the structure of atoms all go into creating a bubble and changing the temperature around it.

Research:

Surface tension occured when liquid molecules acted as cohesive forces and held together

the surface of a liquid. On the very top of the surface, a thin film appeared called the meniscus. The surface tension of water decreased significantly with temperature as shown in the Figure 1. Laplace’s law stated that bubbles tooke up the minimal amount of space possible because of wall tension pulling the bubbles into spherical shapes. Wall tension was also caused by surface tension.

Because bubbles were an enclosed but hallow three-dimensional form, they have pressure on the inside and outside pushing and pulling. If a bubble was split into two hemispheres, it appears that the lower half of the hemisphere has its internal pressure pushing downwards, but is neutralized by surface tension around the circle’s circumference. The pressure difference between the inside and outside of a bubble depended upon the surface tension and the radius of the bubble. Soap and water molecules were sandwiched together in a thin layer. It may seem counterproductive that soap reduced the amount of surface tension in water at first and a bubble would have a difficult time staying together for very long. But while the surface tension lessened, the outer layer expanded to cover a wider area. The concentration of the soap molecules also decreased and the water molecules interact more strongly, increasing its surface tension and stabilizing the bubble as it expanded.

A Pascal was the unit of measuring pressure and if a parcel of air was denser than its surroundings, it would sink and vice versa. Air with a greater percentage of water vapor would be less dense than air with a lesser percentage of water vapor at the same temperature. Absolute humidity was the amount of water vapor in the air but was usually referred to as relative humidity which differs. Unlike humidity, relative humidity was measurde by dividing the amount of water vapor in the air by how much water vapor the air could possibly hold. The colder the air, the less moisture it could hold. Humidity is measured by a hygrometer in percentages ranging from zero to 100. Evaporation occured when a liquid is transitioning to a gas.

When blowing into a straw, a rush of air would come out the other end at high velocity which would burst them. The volume of air into the bubble would remain with a cone shaped bubble blower, as shown in Figure 2, but with a reduced velocity. As soon as the air reached the end of the cone, it has reduced in speed and the bubble fills with more of an even distribution rather than a violent stream of air. A standard plastic ring used on traditional bubble wands causde the bubble solution to cling to the plastic surface and span the opening. When this bubble solution ran out, the bubble would separate from the ring or burst. The size of the bubble was limited by the small amount of soap solution clinging to the ring. Figure 3 showed the absorbent paper cone being submerged into the bubble solution to absorb a large quantity of the soap mixture. Liquid dish washing detergent provided the best solution because it made a thicker bubble if the additional steps of starting with 1 part liquid detergent and 15 parts water were taken. By leaving it stand in an open container overnight, the life span of a bubble made with the solution would improve. An effective way of detaching the blower from the bubble would be by quickly whipping the blower up and down. This was demonstrated in Figure 4. Also, the soap mixture should always be stirred, not shaken, otherwise excessive amounts of suds were produced.

Chelsey Traylor performed a similar experiment to The Effect of Temperature and Atmospheric Condition on the Life Span of a Soap Bubble titled Bubble Life Span & Temperature.

In her Analysis & Conclusions section, Traylor stated, “The life span of the bubbles lasted the longest in the ice water temperature in comparison to the control jar (room temperature) and the hot water. The molecules in the hot bubble solution were moving much faster due to a larger amount of kinetic energy… being heated up in comparison the… molecules in the ice water and room temperature water environments. The bubbles in the hot water environment are evaporating at a much faster rate than in the cold water environment,” (2013). Chelsey Traylor’s experiment showed contrasting ideas and some variation in purpose, but nonetheless displayed information suggesting that this experiment would have comparable results. Another set of trials named Can the Life Span of a Bubble be Extended in Different Temperatures and Atmospheric Conditions? took place by Tricia Edgar around 2006-2011 which was extremely similar beside the incorporation of additional substances. As described in her Results segment, (2006-2011), "Colder bubbles last longer," and this correlated to Traylor's discoveries. "When bubbles pop, they often pop because the water in the bubble evaporates into the environment. Making bubbles cold also helps them last longer because evaporation slows down in colder temperatures,” (Tricia Edgar, 2006-2011). The information collected by both experimenters relate to this experiment’s purpose and previous

research.

Material & Methods:
The independent variable in this experiment was the temperature and atmospheric conditions that each container was held in, including a cold and dry environment (which was referred to as CD further on), a hot and humid environment (which was referred to as HH further on), and a room and mid-humid temperature environment (which was referred to as MT further on). The dependent variable was the amount of seconds each bubble remained intact.

• 3 16-ounce transparent containers
• 3 clear 20-ounce transparent containers
• 3 plastic drinking straws
• 3 cups of water
• 1/8 cup of dishwashing soap

1. Fill three 16-ounce containers with 1 cup of water and ⅛ cup of dishwashing soap each.
2. Stir each container's contents with a fork at a fast pace for 30 seconds.
3. Heat water up to 80° Celsius. Put heated up water into a 20-ounce container holding the soap and water mixture. Place plastic wrap over the top. This is the HH test.
4. Cool water down to 20° Celsius. Put cooled down water into a 20-ounce container holding the soap and water mixture. Place plastic wrap over the top. This is the CD test.
5. Bring water to 30° Celsius. Put room temperature water into a 20-ounce container holding the soap and water mixture. Place plastic wrap over the top. This is the MT test.
6. For each mixture: Submerge a straw one inch into the container. Put mouth on the opposite end of the straw and hold breath. Bring straw out of the container and blow lightly for about 5 seconds. Stop blowing at 5 seconds and without hesitation, hold your tongue against the open end of the straw until the bubble pops. Time how long the bubble remains intact strain as soon as it hits the plate. Repeat process 20 times.

Data & Results:
The stopwatch counted upward in units; when 1,000 milliseconds had passed, it converted automatically to 1 second; when 60 seconds had passed, it converted the time to minutes and so on. Most of the data did not exceed 60 seconds but some did. This made it necessary for the sake of clarity to convert all data to seconds. 1.45(60)=87 seconds.