Rocket Power

Introduction:  

Getting something into outer space is a problem because it has to overcome the mighty force of gravity that tries to pull it back down again. Rockets can overcome this force because they are powered by controlled explosions that occur in the engine of the rocket.  An explosion is an extremely rapid chemical reaction that produces gases and heat. The force of the explosion is produced as liquid or solid particles are quickly converted into gases.  These gases take up a great deal more space and as they expand they push out on their containers (the rocket). This push overcomes the force of gravity and propels the rocket into space. 

In this activity, you will make a simple a “rocket” using a film canister for the rocket and Alka-Seltzer and water for the fuel.

 Purpose:

Your mission in this activity is to find out which set of conditions will produce the longest shooting rockets.

  With each rocket launch could try:

a.      different amounts of Alka-Seltzer

b.      different amounts of water

c.      different launching angles (optional)

Each group will be limited to 4 tablets of Alka Seltzer so break it apart and use it in pieces (more does not necessarily work better).

National Science Standard: Unifying Concept

Nature is predictable and we can use evidence to explain and understand it.

Georgia Performance Standards:

Students will exhibit curiosity, honesty, openness and skepticism S(K-5)CS1

Students will observe and communicate the effects of gravity on an object.  SKP3,S2P3,S4P3

Students will investigate the difference between physical and chemical changes. S5P2

Materials:

Launch Tube             Film canister (rocket)            Alka-Seltzer Tablets

Water                         Plastic Cup or Beaker  

Exploration:

1.         Obtain the materials listed above.

2.         Determine how much water and how much Alka-Seltzer you want to use.

3.         Record on the table below how much of these you will use for the first trial.

4.       When your group is ready to launch, put the piece of Alka-Seltzer in the lid of the rocket.   QUICKLY put the lid on tightly and then drop it lid-side down into the launch tube.

5.       Be patient and wait for it to launch and make sure no one steps into the line of fire. When it launches, measure the distance that it traveled. Record your measurements on the table below.   Repeat this procedure at least 3 more times using different combinations of Alka-Seltzer and water. Try to determine the best combination.

Essential Questions:

1.    According to your results, what combination of Alka -Seltzer and water produced the longest shooting rocket?

2.      Describe how you think the force (push) was produced that caused the rocket to be propelled out  of the launcher.

3.      Besides the amounts of Alka-Seltzer and water, describe two other factors that you think might have some effect on the flight distance of the rocket.

4.     Describe and draw two design changes in the rocket or launcher that you think  your could make the rocket go further. 

Explanation

Bring the class back together and discuss their results and ideas. You may choose to focus the discussion on process objectives such the importance of setting up good experiments and making good measurements. You may also concentrate on key ideas needed to build their understanding of motion and/or chemical reactions.

Concept Discussion:

This experiment can be used as activity to start off the year when you are discussing the nature of science, or it can be used as part of your study of motion, forces or chemical reactions.  In each case, it is safe and fun opportunity for kids to explore their ideas in these areas. 

It is important for kids to realize that what we have learned in science has come about from doing experiments that attempt to solve some type of problem. In this case the problem is to find a combination of rocket fuel (Alka Seltzer and Water) that will propel a rocket further.  If time and materials permit, feel free to let your students investigate other factors that they think might improve flight distance.  

Although this activity can be a bit loud and messy, the rockets themselves are very safe and the speeds produced during their launching are insufficient to cause any harm.  Even so, students should be warned not to point the rockets at inappropriate targets and they should make sure to drop the rockets into the canisters top side down when they are launching.

Newton's Law of Action and Reaction states that when an object is pushed (the action), it pushes back with an equal and opposite force (the reaction). When water is added to Alka-Seltzer tablets, a chemical reaction occurs and carbon dioxide gas is released as a product of the reaction. As these gas particles rapidly spread apart from one another the pressure inside the rocket increases. As the gases push off on the rocket (the action), the rocket pushes off on the gases (the reaction) and the rocket is propelled through space.  Bullets from a gun and balls from a cannon work in a similar manner.