Bio 1-1 Adhesion/Cohesion Lab

Adhesion and Cohesion Lab

GROUP MEMEBERS:

Adhesion and cohesion in water are among the most important biological chemical properties. Water molecules have weak positive and negative charges. This weak polarity is what allows water molecules to be attracted to each other (cohesion) and to other items (adhesion). This property is also responsible for water being a very good solvent of polar molecules (such as salt, sugar and many of the minerals in your diet). This quick lab will demonstrate how adhesion and cohesion work and how they are affected by the solutions in water.

Materials for groups of two or three:

12 pennies

Pipette or eyedropper (use a clean pipette for each solution)

150 ml of distilled water (preferred, but tap water will work)

sugar solution:Thoroughly mix 50 ml of corn syrup with 100 ml of tap water.

salt solution: Thoroughly mix 20 grams of table salt into 100 ml of tap water.

Procedure:

Using a clean pipette, slowly and carefully place one drop at a time of distilled water onto a penny until the water spills off onto the table. Keep the pipette about 1 cm from the penny to minimize splash but do not touch the pipette to the water on the penny.Record the result in the data table and run three replications. The mean of these data is your baseline.

Predictions:

Based on your baseline number, and your understanding of water chemistry, predict how many drops it will take to spill over on each of the different solutions and record your predictions in the data table.

Repeat this procedure of each of the remaining solutions.

Baseline average for distilled water:

Prediction for sugar solution:

Prediction for salt solution:

Prediction for third solution:

Data Table

Penny 1 / Penny 2 / Penny 3 / Penny 4 / Mean
Distilled water
Sugar Solution
Salt Solution

Analysis

Considering the adhesive and cohesive nature of water and the observations recorded, construct a hypothesis to explain the data. Use scientific language and back your hypothesis with well-reasoned justifications.

Competencies / 0 / Emerging (1) / Capable (2) / Bridging (3) / Proficient (4) / Advanced (5)
S01. Scientific Investigation: Demonstrate an understanding of different kinds of scientific investigation, controlled experiment, fieldwork, experimental design, and secondary research. / Define different types of a scientific investigation.
Recognize or recall the characteristics and/or steps of a scientific investigation.
List observable data. / Explain how different types of investigations can be used to answer scientific questions and investigations.
Describe the role of collected observable data in the investigation process.
Develop a hypothesis, conduct a pre-designed scientific investigation, and describe the results. / Collect and classify observable data.
Conduct a scientific investigation and analyze the results to determine if it satisfactorily addresses the hypothesis. / Analyze the roles of collected observable data in the scientific investigation process.
Evaluate the design and results of an investigation to determine if it satisfactorily addresses the hypothesis. / Develop and conduct an investigation to test a hypothesis and analyze the results.
Determine the value of collected observable data in completing the scientific investigation process and proving the hypothesis.
Suggest other plausible observable data that could be collected to support the scientific investigation process.
PO6. Cooperation
Standards / 0 / Emerging (1) / Capable (2) / Bridging (3) / Proficient (4) / Advanced (5)
Standard 1: Cellular Chemistry
Describe the basic molecular structure and function of the four major categories of organic compounds essential to cellular function. B.1.1 / Present for lab, but did not contribute in a meaningful way. Depended upon partner to do most of the work. / Followed procedures but little effort was made to ensure accuracy, and there is little evidence that the student connects the data to the stated hypothesis. / Lab procedures were completed with reasonable accuracy.
Hypothesis connects minimally with the data (reasoning). / All lab procedures were followed accurately and data appears reasonable for this lab.
Hypothesis matches the hypothesis; student clearly connects the hypothesis to the data. / Very careful and accurate procedures.
Data is tied directly to hypothesis.
Hypothesis shows exceptional reasoning based on data.