Surface Area Demonstration

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Objective

Students will be able to observe that increasing the surface area of airborne powdered sugar provides a combustion reaction.

Big Idea

Fire = Student's Attention

NGSS Background

This lesson is based on California's Middle School Integrated Model of NGSS.

NGSS Performance Expectation (PE): (MS-PS1-2) Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occured.

Science and Engineering Practice SP4: Analyze and Interpret Data.

Disciplinary Core Ideas (DCI): PS1.A: Structure and Properties of Matter - Substances are made from different types of atoms, which combine with one another in various ways. Atoms form molecules that range in size from two to thousands of atoms.

Crosscutting Concepts (CCC): Cause and Effect

The goal of this lesson is to familiarize my students with (1) combustion reactions, and (2) that surface area increases the rate of chemical reactions (MS-PS1-2). When the surface are is limited, as with a pile of powdered sugar, the molecules are too closely packed together and there is not enough oxygen surrounding the sugar molecules to permit combustion; the sugar and oxygen react in predictable ways (PS1.A). By observing this reaction students are able to determine for themselves that oxygen is important for combustion reactions and that the proper sugar/air ratio allow for this combustion reaction (SP4). By observing the cause (proper sugar/oxygen ratio) students are able to determine the effect (combustion) by knowing the principles of the periodic table (predictable patterns) (CCC).     

This lesson is design to allow my students to use models to develop and engage scientific thinking, while improving their use of scientific vocabulary.

Set-Up

10 minutes

This reaction requires a fairly simple to set-up, but it can be difficult to perform.

  1. Fill a plastic ketchup bottle with powdered sugar. For best results I have found that filling it less than half full provides a better flame.  
  2. Hold a kitchen lighter in front of the bottle and carefully squeeze the bottle, causing the powdered sugar to shoot out of the end of the ketchup bottle. The trick seems to be getting the sugar air mixture just right in order to ignite the sugar.

BEWARE OF FIRE SPRINKLERS OVERHEAD

Demonstration

5 minutes

Prior to performing this demonstration I review the factors that increase the rate of a chemical reaction (concentration, surface area, temperature, catalyst). We discuss that by increasing the surface area of powdered sugar and allowing the powdered sugar particles to be surrounded by more oxygen molecules combustion can be achieved. We also review that combustion requires fuel (powdered sugar), oxygen (in the air), and a spark (kitchen lighter). Firefighters are taught combustion reactions as the 'fire triangle' The fire triangle states that fire can only exist if there are three conditions: (1) oxygen, (2) fuel, and (3) a spark. If any three points of the triangle is denied a fire CANNOT exist (same is true of a combustion reaction).

I also place the following chemical reaction on the board for reference.

Student Activity

40 minutes

As a review activity the students must create a diagram explaining why surface area increases the rate of a chemical reaction. They may use past assignments/notes from their Science Notebook or use Michael Tinnesand's 2010 article from ChemMatters: SUGAR - An Unusual Explosive. 

Each diagram must contain:

  1. Title
  2. Labels
  3. Three color minimum
  4. Description

Student Work

 

Extension

20 minutes

To complement this lesson I have created two PowerPoint lessons, with mnemonic sentences to help students retain information.

1) Types of Chemical Reactions 

Squids don't carry roses.

  1. synthesis reactions
  2. decomposition reactions
  3. combustion reactions
  4. replacement reactions

2) Rates of Chemical Reactions

Camels swim to Catalina (Catalina is an island off the coast of Southern California that our students visit to attend a science camp).

  1. concentration
  2. surface area
  3. temperature
  4. catalyst