Experiment 1: Preparing Graphs – Candle Mass vs. Time

Experiment 1: Preparing Graphs

Introduction to Experimental Data Collection

This experiment introduces students to the process of collecting quantitative data and representing it graphically. The focus is on measuring the mass of a candle as it burns over time, recording the data, and analyzing the results using a best-fit line.

• Objective: To measure the change in mass of a burning candle over time and represent the data graphically.

• Application: Understanding data collection, graphing, and linear relationships in chemistry experiments.

Materials and Procedure

• Materials: Candle, weighing paper, graph paper.

• Procedure:

  1. Measure and record the mass of the weighing paper alone.

  2. Measure the mass of the candle plus weighing paper; calculate the mass of the candle alone.

  3. Light the candle and allow it to burn for 10 minutes, keeping all drippings on the weighing paper.

  4. After 10 minutes, extinguish the flame and weigh the candle plus weighing paper again; calculate the new mass of the candle.

  5. Repeat the burning and weighing process for four additional 10-minute intervals (total of 50 minutes).

  6. Record all mass measurements in a table.

Data Table: Mass of Candle Over Time

The following table summarizes the mass measurements taken at each time interval. The mass of the candle is calculated by subtracting the mass of the weighing paper from the total mass.

Time (minutes)	Mass (Candle + Weighing Paper)	Mass (Candle)
0	0.840	0.689
10	0.751	0.602
20	0.652	0.503
30	0.563	0.414
40	0.474	0.325
50	0.385	0.236

Additional info: Some values have been inferred for clarity and completeness.

Graphing the Data

To analyze the relationship between the mass of the candle and time, plot mass (y-axis) versus time (x-axis) on graph paper. The resulting graph should show a decreasing trend, indicating the candle loses mass as it burns.

• Best-Fit Line: Draw a straight line that best represents the data points. This line models the linear relationship between mass and time.

• Slope (m): The slope of the line represents the rate at which the candle loses mass per minute.

• Y-intercept (b): The y-intercept is the initial mass of the candle at time zero.

Equation of the Line

The equation for the best-fit line is given by:

$\text{Mass} = m \times \text{Time} + b$

• m: Slope (change in mass per unit time)

• b: Initial mass of the candle (at t = 0)

Example Calculation:

Suppose the mass decreases from 0.689 g at t = 0 min to 0.236 g at t = 50 min. The slope is calculated as:

$m = \frac{0.236\,\text{g} - 0.689\,\text{g}}{50\,\text{min} - 0\,\text{min}} = \frac{-0.453\,\text{g}}{50\,\text{min}} = -0.00906\,\text{g/min}$

Thus, the equation of the line is:

$\text{Mass} = -0.00906 \times \text{Time} + 0.689$

Key Concepts

• Linear Relationship: The mass of the candle decreases linearly with time as it burns.

• Data Analysis: Graphing experimental data helps visualize trends and calculate rates of change.

• Best-Fit Line: Used to model the relationship between variables and make predictions.

Applications in Chemistry

• Mass Loss in Chemical Reactions: Burning a candle is a combustion reaction where wax (hydrocarbon) reacts with oxygen to produce carbon dioxide and water vapor, resulting in mass loss.

• Experimental Design: Accurate measurement and data recording are essential for reliable results in chemistry experiments.

Additional info: This experiment is foundational for understanding data analysis, graphing, and interpreting linear relationships in GOB Chemistry.