Toy Bomb Bags
There’s a surprise inside.

Introduction
Science is the observation, identification, description, experimental investigation, and theoretical explanation of natural phenomena. Over the last half millennium, scientists have developed a method to aid them in learning about the Universe we inhabit. In this experiment, you will use the Scientific Method to investigate how a popular toy called a “bomb bag” works.

The steps in the Scientific Method are not necessarily sequential and not all of them have to be performed to conduct a successful investigation of natural phenomena. Nonetheless, the steps are listed in a logical order below that could be followed from start to finish.
scientific method.JPG


Vocabulary
Millennium – a period of 1000 years
Method – series of steps used to solve a problem
Phenomena – a fact, occurrence, or circumstance observed or observable
Observation – any information gathered using your senses
Hypothesis – educated guess; a well thought out solution to a problem
Variable – any factor in an experiment that could affect the results and is therefore, tested separately.
Controlled Experiment – an experiment in which all variables except the one being tested are controlled in order to make the experiment fair and the results reliable.


Define the Problem
What causes a toy store “bomb bag” to explode? Specifically, we want to know what is happening on the inside to make the bag inflate and eventually pop.


Make Observations
Materials
  • Gloves
  • Goggles
  • Plastic container with lid
  • Bomb Bag
  • Scissors

Method - when your instructor tells you to do so:
  1. Put on goggles and gloves.
  2. Obtain a “bomb bag” and a plastic container with a lid.
  3. Put the lid flat on your table top.
  4. Press the center of the bomb bag to activate it and put the container over its lid. In this way, the bomb bag explosion can be viewed without making a mess.




figure1.jpg
Figure 1: Exploding a toy Bomb Bag in a container.




Using your senses (do NOT taste); record your observations of the exploding bag before, during and after it explodes.


After you press the bag but before it explodes
While the bag is exploding
After the explosion

Next, obtain a new bomb bag and some scissors. Place the bomb bag in your plastic bin (so you don’t make a mess). Carefully cut open the bomb bag and observe the contents. What is inside the bag?

figure2.jpg
Figure 2: Contents of a non-exploded toy bomb bag.

Okay, now cut open the small bag and pour it onto the white, grainy substance. What happens?



Record your observations of the contents of a non-exploded bomb bag, and also your observations of when the liquid in the small bag was mixed with the white substance.

Observations of a non-exploded bomb bag
Observations when the liquid in the small bag are poured onto the white substance

Finally, we would like to know exactly which chemicals can be found inside a bomb bag. Four different possible substances will be given to you, and it is your job to narrow down which 2 are actually inside a bomb bag. Make careful observations, using your senses, of the substances in the space below. (Remember, NEVER taste any substances in Science class unless instructed to do so by your teacher. Do NOT taste these substances).

Baking Soda
Citric Acid
Salt
Sugar

Research the Topic
In order to understand the chemical reaction occurring inside of a bomb bag it is important to understand a few different chemical concepts. Perform research to answer the following questions. A web link is provided to assist you.

1. What is a chemical reaction?
http://www.chemicalformula.org/basic-chemistry/chemical-reactions







2. What is an acid?
http://www.chemicalformula.org/reactions/acids-and-bases


3. What is a carbonate compound?
http://www.chemicalformula.org/reactions/acid-carbonates



4. What happens when an acid and a carbonate compound react?
http://www.chemicalformula.org/reactions/acid-carbonates (scroll down)







Next, on your own research the 4 potential substances used in the making of bomb bags. Try to find out at least two useful things about each one, such as if they are an acid, if they are a carbonate compound, and what their chemical formula is, e.g. water’s chemical formula is H2O. Record your research findings in the table below:
Baking Soda
Citric Acid
Salt
Sugar

Form Hypothesis
Form a hypothesis as to how a bomb bag works. Specifically, list which 2 chemicals (with water) you believe are inside of the bag and explain how they interact to make the bag explode. Write your hypothesis in the space below.






Design an Experiment
With the materials provided, design a simple experiment to test which substances when mixed inflate and explode the bomb bag. You will need to include water as one of the materials in order to properly mix the chemicals. Additionally, don’t forget lab safety equipment. Write your materials and method below.

Hint: check out the available supplies.

Materials










Method










Ensuring it is a controlled experiment
The type of experiment you are performing is a controlled experiment. A controlled experiment should have 2 parts: a control and a variable. The control should be what normally occurs, or what is natural, and variables that could possibly affect the outcome of the experiment are controlled (hence the name). The control is used as a basis for comparison.

In the variable, only one thing is allowed to differ from the control. If 2 or more variables differ from the control, it is not possible to decide which variable affected the outcome. Ideally, we end up having two identical setups and allow only one thing to change. The part of the experiment where the one thing has changed is the variable.

With any controlled experiment the variable that you purposely change is called the independent variable. It is what you change first. Then after you make that change you see how something changes in response to what you did. What you measure second is called the dependent variable. You want to see if the dependent variable depends on the independent variable.

Independent Variable – a variable that you purposely manipulate (change). This is changed first.

Dependent Variable – the variable being observed that changes in response to the independent variable. This is measured second.

Answer the following questions about your experiment.
1. What is the control of your experiment?



2. What is the independent variable?




3. What is the dependent variable?




Experiment
Conduct the experiment and record the results of your experiment below – record your data in the table. Do NOT fill in the squares with X's (these are unnecessary or duplicate reactions).


Baking Soda
Citric Acid
Salt
Baking Soda
X
X
X
Citric Acid

X
X
Salt


X
Sugar



Table 1: Observations of Reactions of Four Pairs of Substances with Water


Analyze Data
Review the data in Table 1. Which pairs of substances reacted with water?








Draw Conclusions
What two substances do you believe are in the bomb bag? Give evidence to support your answer.


Communicate Results
In a paragraph summarize the results of your experiment and share your findings with the class.







Explanation
Inside the bomb bag is a mixture of citric acid (chemical formula: C6H8O7) and sodium bicarbonate (common name: baking soda; chemical formula: NaHCO3). Additionally in the bag is a small packet of water. When the bomb bag is pressed firmly the small packet of water bursts allowing the citric acid and sodium bicarbonate to mix and react. Whenever an acid and a carbonate compound mix they react chemically to form a salt, water and carbon dioxide gas. The carbon dioxide gas which forms inflates the bag and eventually causes it to burst. The bag is likely made from Mylar, a type of plastic that is very good at containing gases and is often used for helium balloons.

A general word equation to explain the chemical reaction is below:

Acid + Metal carbonate àSalt + Water + Carbon dioxide

A word equation and a chemical equation for the specific chemical reaction for the bomb bag are given below:

Citric acid + sodium bicarbonate yields sodium citrate + water + carbon dioxide

C6H8O7 + 3NaHCO3 à C6H5Na3O7 + 3H2O + 3CO2

Extension #1
After the Toy Bomb Bag activity is complete have students observe Alka-Seltzer tablets dropped in water. Without allowing them to look at the ingredients on the box, have students make an inference about what substances must be in the tablets to cause them to fizz. After they have come up with a reasonable guess have them check their answer by reading the active ingredients on the box. What they will discover is that citric acid and baking soda are found in Alka-Seltzer. The third active ingredient, aspirin, is not involved in the fizzing.
alkaseltzer.jpg
Figure 3: Alka Seltzer in water is another example of a citric acid and baking soda reaction.


Extension #2
Another activity that can be performed after the Toy Bomb Bag activity involves the popular candy Smarties and some baking soda dissolved in water. Have students get one Smartie from a pack of Smarties and 2 spoons. One Smartie is placed in a spoon, and the other spoon is placed on top of it. Then the spoons are pushed together and rotated to crush the Smartie. Next some baking soda and water can be mixed up in a cup or beaker, and a few drops of the baking soda water can be dropped on the crushed pieces of the Smartie. Careful observations reveal a fizzing reaction caused by the citric acid in the Smartie reacting with the baking soda.
smartiesbakingsoda.jpg
Figure 4: Crush some Smarties, drop some baking soda water on them, look for the fizz



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