7th Grade Science Demonstration - Surface Tension

Title:                     Water Molecule Bonding Time

Grade Level:        Variable

Concept:               When water molecules bond together, they form a phenomenon known as surface tension.

Standard:             S.IP.07.11 Generate scientific questions based on observations,investigations, and research.

(MI GLCEs)         S.IP.07.12 Design and conduct scientific investigations.

                              P.PM.07.24 Describe examples of physical and chemical properties of elements and compounds (boiling point, density, color, conductivity, reactivity). http://www.michigan.gov/documents/mde/Complete_Science_GLCE_12-12-07_218314_7.pdf

Materials:             cloth handkerchief or bandana, drinking glass, container of water, food coloring, pencil and paper for recording predictions and observations

Precautions:         This demonstration should be conducted away from any objects that could be damaged by water.


Procedure:      §  Drape the handkerchief over the glass, making sure that you push the center of the handkerchief down into the glass.

§  Fill the glass three-quarters full with water, by pouring all the liquid into the middle of the handkerchief.

§  Stretch the handkerchief tightly across the surface of the glass, then grip the ends of the handkerchief at the bottom of the glass.

§  Place one hand over the mouth of the glass and turn it over with the other hand.

§  Pull the lower hand away from the glass (slowly) and the water should stay in the glass.

§  Next, place your hand over the mouth of the glass and turn the glass right side up again. Remove the handkerchief from the glass and pour the water back into the container.

Explanation:        The water didn’t leak because it went through the handkerchief as it was poured into the glass. The microscopic spaces between the threads in the handkerchief disappeared when the cloth was stretched tightly across the mouth of the glass as they were filled in with water molecules. This action allowed the water molecules to bond to one another, by the phenomenon known as “surface tension.” Surface tension prevented the water from seeping through the handkerchief.

Extensions:           Art- Students could illustrate their predictions and observations

                              Language Arts- Students could write about their observations and predictions

                              Math- Student could measure and compare the starting and ending amount of water in the container to ensure that no water has left the glass.

Source: http://www.education.com/activity/article/Surface_Tension_Suprise_fourth/