BIOS 251 Week 2 Lab Instructions Chemistry Basics

Student Name

Chamberlain University

BIOS-251 Anatomy & Physiology I

Prof. Name

Date

Lab Instructions: Chemistry Basics

Activity Overview and Points Distribution

The laboratory activities are divided into different parts, each contributing specific points to the final grade. The table below summarizes the deliverables and associated points.

Table 1

Step 1: Review of Laboratory Materials

Students must carefully review the entire laboratory packet prior to beginning any activities. This preparation ensures familiarity with procedures and safety protocols.

Step 2: Laboratory Safety and PPE

Background: Acids and Bases

Acids and bases are fundamental chemical substances defined by their pH values. The pH scale generally ranges from 0 to 14, where values below 7 indicate acidity and those above 7 indicate basicity. A pH of 7 is neutral, as seen in pure water. Acids are proton (H⁺) donors, while bases accept protons, influencing biological and chemical systems.

Buffers

Buffers are solutions that resist drastic changes in pH. They are essential in both biological and industrial contexts. For instance, phosphate buffers are used in contact lens solutions to maintain a stable pH similar to that of human tears, protecting ocular tissues from irritation.

Solutions

A solution consists of a solute (minor component) and a solvent (major component). Unlike suspensions, solutions remain homogenous over time and do not separate. Understanding solution preparation is crucial in healthcare and laboratory science.

Purpose of the Experiment

The goal of this lab is to investigate the properties of common acids, bases, and buffers, while also exploring solution preparation. Students will:

• Practice measuring pH using both strips and a pH meter.

• Examine the impact of strong acids on buffer stability.

• Compare the neutralizing capacity of different antacids.

• Learn to prepare standard solutions such as normal saline.

Materials Needed

• Laboratory packet (printed copy for each student)

• Writing utensils

• Instructor demonstration setup

• DI (deionized) water, lemon juice, bleach, HCl solutions

• Antacids (Tums, Alka-Seltzer)

• pH strips and pH meter

Preparation Guidelines

Before entering the laboratory, students must:

• Read the full packet thoroughly.

• Remove unnecessary items from the workspace.

• Safely store personal belongings.

• Collect all required materials.

• Pay attention to safety instructions from the instructor.

• Record their own data and prepare individual lab reports, even when collaborating.

Activity Guidelines

Students are expected to:

• Complete observations.

• Fill in data tables accurately.

• Answer all questions in detail.

• Use textbooks and lecture notes as references to support conclusions.

Observation Report: Week 2 Chemistry Basics

Measuring pH

Body systems maintain distinct pH levels for optimal function. For instance, blood pH normally ranges between 7.35–7.45, supporting proper enzyme activity and oxygen transport. This experiment evaluates the pH of various household substances to classify them as acidic or basic.

Part A: Measuring pH with Strips

Materials: DI water, lemon juice, bleach, unknown solutions

Procedure:

1. Collect a pH strip for each test solution.

2. Dip the strip into the liquid sample.

3. Compare the strip color with the reference chart.

4. Record the pH and classify the solution.

Table 2

Part B: Measuring pH with a pH Meter

Using a pH meter provides more precision than strips.

Table 3

Questions and Answers

1. Based on your pH measurements, determine which unknown solution corresponds to HCl or NaOH.

   • Unknown A or B can be identified depending on whether the pH is strongly acidic (HCl) or strongly basic (NaOH).

2. Note any trends observed regarding the acidic solutions.

   • Acidic solutions consistently show lower pH values across both testing methods.

3. Does the pH of the blood sample suggest it is from a healthy individual?

   • A reading between 7.35 and 7.45 indicates a healthy sample. Values outside this range may signal acidosis or alkalosis.

Part C: Effect of Strong Acids on Buffers

This activity explores how HCl affects water compared to a buffer solution.

Table 4: Experimental Data

Questions and Answers

1. What effect does adding 1 M HCl have on the pH of the buffer solution?

   • The buffer maintains a nearly constant pH, demonstrating resistance to change.

2. Create a graph of pH versus drops of 1 M HCl.

   • A graph would show rapid decline in water pH but a flat trend for the buffer.

3. Describe the rate of pH change observed in the graph.

   • Water shows steep pH decline, while the buffer remains stable.

4. Compare the changes in pH for DI water and the buffer solution.

   • Unlike DI water, the buffer prevents significant changes, highlighting its stabilizing properties.

Part D: Comparing Antacids

Stomach acid has a molarity of about 0.36 M HCl. Antacids help neutralize excess acidity.

Table 5: Antacid Comparison

Questions and Answers

1. Are the active ingredients of the antacids acids or bases?

   • They are bases, used to neutralize stomach acid.

2. How does the active ingredient change the pH of the stomach acid?

   • It reacts with HCl to form neutral salts, raising the pH.

3. Calculate the total active ingredient required based on your results.

   • The calculation depends on the moles of HCl neutralized by each tablet.

Part E: Solutions

Normal saline preparation demonstrates solution concentration and osmolality.

Questions and Answers

1. What percentage concentration should be labeled on the bag?

   • A 0.9% NaCl solution is the standard concentration.

2. Given a molarity of 0.154 M NaCl, what osmolality would you expect?

   • Approximately 308 mOsm/L, since NaCl dissociates into two particles.

3. If evaporation occurs during sterilization, how would it affect concentration?

   • The concentration would increase as the solute mass remains the same while solvent volume decreases.

Reflection

Through this lab, students learn the importance of pH measurement techniques, the stabilizing role of buffers, the chemistry of antacid neutralization, and the preparation of clinical solutions like saline. These concepts bridge theoretical knowledge with real-world medical and laboratory practices.

Grading Rubric

Table 6: Points Allocation

References

Saladin, K. S. (Year). Anatomy & Physiology: The Unity of Form and Function. Publisher.

Tortora, G. J., & Derrickson, B. (2019). Principles of Anatomy and Physiology (15th ed.). Wiley.

BIOS 251 Week 2 Lab Instructions Chemistry Basics

Zumdahl, S. S., & Zumdahl, S. A. (2020). Chemistry: An Atoms First Approach (3rd ed.). Cengage Learning.