Properties of Water: Lab Report

Introduction:

Water consists of two hydrogen and one oxygen atoms. Since oxygen atoms have a greater electronegativity than hydrogen atoms, electrons shared between the covalently bonded atoms of water molecule will experience a greater pull towards the oxygen atom. This will create partial charges, making oxygen atom slightly negative and hydrogen atoms slightly positive. That makes water molecule a polar molecule. Since opposite charges attract in nature, a slightly negative end of a water molecule will be attracted to the slightly positive end of a neighboring molecule and vice versa. This weak attraction is called hydrogen bonding and is what gives the water its cohesive properties.

The purpose of this lab is to test whether adding different types of substances to the water affects the hydrogen bonding between the solution molecules.

Hypothesis:

If solutions are formed by adding different type of substances into water, the strength of the hydrogen bonding between the molecules of the solution will be affected. Therefore, for different types of solutions, the average number of drops a penny will hold will change.

Materials and Procedures:

Independent Variable: Type of solution

Dependent Variable: Number of drops

Control Variable: Penny

Procedure:

1. First, fill each of the three cups with a different type of solution. Solution types include water, water+sugar, water+soap.

2. Obtain a dry penny and place it on top of a dry paper towel.

3. Using a pipet, draw a sample of a solution from the one of the cups.

4. Add the solution to the penny drop by drop using the pipet and count the number of drops until the penny overflows.

5. Record the number of drops on the table.

6. Repeat steps 2-5 for 5 trials for the same type of solution.

7. Repeat steps 2-6 for other types of solution.

Data Table:

Graph:

Analysis:

Mean of the number of drops of water is greater than the mean of the number of drops of water+soap. However, mean of the number of drops of water+sugar is greater than the mean of the number of drops of water. Basically, we can compare the means like the following:

MeanWater+Sugar>MeanWater>MeanWater+Soap

Conclusion:

• Since mean of average drops of water+soap (11.6) is less the mean of average drops of water (26.6), adding soap to water weakened the hydrogen bonds between the solution molecules.

• Since mean of the average drops of water+sugar (34.6) is greater than the mean of average drops of water (26.6), adding sugar to water strengthened the hydrogen bonds between the solution molecules.

• Results summarized above support the hypothesis that adding substances to the water will affect the hydrogen bonding between the solution molecules.

• Some possible error may be that every drop of solution on the penny might not be of the same size due to the fact that the force applied to the pipet was not the same every time. However, the affect of this error was minimized by taking the mean of five trials.

• This experiment might be conducted with several more different types of solutions to gather more evidence to either support or refute the hypothesis in the future.