# 1B. Critiquing IA Explorations

As a step towards preparing your IA Exploration, you should learn how to be critical. It is considerably easier to be objective to someone else's work than your own, so let's give that a try here. Spend 15 minutes reading and commenting on Example Elephant's Exploration, then click on the Feedback link to see what I think. You will need to search and read in order to make intelligent judgment.

A PDF version for print annotation is available here.


# Example Elephant’s IA Exploration

# Research Question

Does acidity change the rate of aspirin hydrolysis?

# Hypothesis

Because acid breaks down molecules, I predict that the higher the pH, the higher the rate of aspirin hydrolysis. When we plot a graph of rate vs pH, it will be linear with a positive slope. The line intersects the origin because at 0 pH there is no acid and so no decomposition.

# Background

Aspirin, also known as acetylsalicylic acid, is a medication used to treat pain, fever, or inflammation. Specific inflammatory conditions which aspirin is used to treat include Kawasaki disease, pericarditis, and rheumatic fever. Aspirin given shortly after a heart attack decreases the risk of death. Aspirin, an acetyl derivative of salicylic acid, is a white, crystalline, weakly acidic substance, with a melting point of 136 °C (277 °F),[3] and a boiling point of 140 °C (284 °F).[133] Its acid dissociation constant (pKa) is 3.5 at 25 °C (77 °F).[134]

Acid breaks down molecules. We know this because, in the stomach, hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids, a process known as protein hydrolysis (IB Chemistry Book). The same should also apply to aspirin.

# Method

  1. Make a solution of 10.00 gram of aspirin in 100 cm3 of water.
  2. Add 1.0 M HCl until the solution is pH 1.
  3. Put solution in a water bath at 10 degrees (to make sure it is constant).
  4. Measure the concentration of aspirin every 10 second for 10 minutes. Write down the values.
  5. Repeat steps 1-4 FIVE times to get uncertainty.
  6. Repeat steps 1-5 at pH 2, 3, 4, 5.

# Data Analysis

Plot a graph of Concentration of Aspirin against pH. Make a best fit line and measure the slope to show the hypothesis to be correct.

See my comments on Elephant's draft in a Google Doc here. A Word version of the Exploration with comments can be downloaded here.

Last Updated: 2 years ago