Light a Match with Water Demonstration

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Objective

Students will be able to observe super-heated steam being used to light a match.

Big Idea

Ever thought ordinary water couldn't be used to light a match – think again!

NGSS Background

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

PE: MS-PS1-4 - Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

DCI: PS1.A – Structure and Properties of Matter: The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.

S&E Practice 2: Developing and Using Models, 8 Obtaining, evaluating, and communicating information

CCC: Cause and Effect

This demonstration is adopted from Steve Spangler's Super Heated Steam. It involves a rig that will allow you to super-heat steam to a temperature that will light a match. You will be providing a model that first causes water to boil, which causes water molecule to leave their liquid state (SP2). The water molecules increase their particle motion and boil into a gaseous state. (MS-PS1-4). This change of state can be predicted based on what we know about water molecules (PS1.A).

Once the steam (gaseous water) exits a flask it travels through copper tubing, which is heated with propane torches.  The steam is able to absorb a great deal of thermal energy, to the point of match ignition. Your students will obtain information about the liquid and gaseous states of water, along with specific properties of super-heated steam (SP8). Understanding that this demonstration super-heats steam (cause) and that super-heated steam can light a match (effect) connects this model to past and future science lessons (CCC: Cause and Effect).

I have two purposes for this activity, 1) I want my students to be able to discuss with me the nature of gasses and that a gas can absorb a tremendous amount of heat before changing to another phase (plasma) and 2) I want to expose my students to different model that replicate the impossible (lighting a match with water).

Set-up

120 minutes

Material needed for rig: hot plate, large flask, rubber stopper, 4 feet of 1/8-inch copper tubing (found in any hardware store) 6 inches of 2-inch pvc pipe, two propane torches, tongs, strike anywhere wooden matches, distilled water, protective gloves, trivet, eye protection.

Directions for building the rig: Make sure the rubber stopper fits snugly in the flask. Carefully coil the copper tubing around the 2-inch pipe, leave about six inch at either end straight. Drill a hole in the rubber tubing and insert the straight end of the copper tubing through the rubber stopper.

Demonstration

10 minutes

TIP: I use distilled water so as not to leave any residual salts in the flask. Ordinary tap water will work fine.

1)   Fill the flask with distilled water, place on the hot plate and bring to a boil.

2)   Once the water has begun to boil insert the rubber stopper with the copper tubing.

3)   Steam should pour out of the copper tubing along with spitting water.

4)   Light both propane torches and heat the copper tubing. The steam exiting the copper tubing will become invisible as it become super-heats.   CAUTION – steam will be very hot.

5)   Continue heating the copper tubing until portions of it become red hot.

6)   Using the tongs hold a wooden match at the exit point of the copper tubing. It should flare to life. IF the match doesn’t light continue heating the copper tubing.

Post-demonstration

10 minutes

I lead a class discussion about the properties of water, boiling, and super-heated steam. I mainly concentrate on the boiling point of water (100° C) and how once water has reached the gaseous phase it can absorb a lot more heat until it reaches yet another phase change (plasma).

Extension

45 minutes

I have included a PowerPoint that explains the different phase changes between solids, liquids, and gases.

1)   Changes of State

and a PowerPoint helping students memorize these changes of state in a mnemonic sentence.

2)   Changes of State 2

If you would like to go into more detail about other phases of matter I have include another PowerPoint describing five states of matter.

3)   More States of Matter

This PowerPoint describes five states: Bose-Einstein, Solid, Liquid, Gas, and Plasma. I wrote a mnemonic sentence to help remember them.

            Bob saw large gilled pike.