Stage 3 – STEM Activity 11
Blow it up
Description of activity
Students investigate how to inflate a balloon using a chemical reaction. They will carry out a trial-and-error process to find the appropriate quantities and address the importance of control measures and accurate measurement.
This activity will take approximately 3 x 45- minute lessons, for students to:
- investigate the reaction of bicarbonate of soda with vinegar
- devise a fair test that will generate data
- carry out the experiment and collect data to solve the problem.
Context
Students recognise that gases inflate balloons. Students will investigate how much bicarbonate of soda should be added to an amount of vinegar to release enough gas to inflate the balloon to a height or circumference of 15cm. Students devise a way to get the bicarbonate of soda into the vinegar to minimise any loss of gas.
Outcomes
Skills
ST3-4WS investigates by posing questions, including testable questions, making predictions and gathering data to draw evidence-based conclusions and develop explanations
ST3-5WT plans and implements a design process, selecting a range of tools, equipment, materials and techniques to produce solutions that address the design criteria and identified constraints
MA3-1WM describes and represents mathematical situations in a variety of ways using mathematical terminology and some conventions
MA3-2WM selects and applies appropriate problem-solving strategies, including the use of digital technologies, in undertaking investigations
MA3-3WM gives a valid reason for supporting one possible solution over another
Knowledge and understanding
ST3-12MW identifies the observable properties of solids, liquids and gases, and that changes made to materials are reversible or irreversible
ST3-16P describes systems used to produce or manufacture products, and the social and environmental influences on product design
MA3-11MG selects and uses the appropriate unit to estimate, measure and calculate volumes and capacities, and converts between units of capacity
MA3-15MG manipulates, classifies and draws two-dimensional shapes, including equilateral, isosceles and scalene triangles, and describes their properties
MA3-18SP uses appropriate methods to collect data and constructs, interprets and evaluates data displays, including dot plots, line graphs and two-way tables
Resources
- Round balloons, 600ml plastic bottles, funnel, container or sand to keep bottle stable, strong cardboard
- instruments to measure volume, eg various measuring cups and teaspoons
- Bicarbonate of soda, vinegar
- Protective gloves, eye wear and clothing
Work, health and safety
- Check relevant Work, health and safety guidelines.
- Vinegar can stain/damage clothes. Students should wear protective clothing and gloves or wash hands after each attempt.
- Bicarbonate of soda can cause eye damage. Wearing science glasses or goggles is advised.
- Balloons may pop – students need to be prepared for this. Wearing science glasses or goggles is advised.
Evidence of work for assessment purposes
- A labelled diagram of the tool the student made to measure the height/circumference of a balloon consistently
- A description of the method used to test and measure how much bicarbonate of soda is needed to blow up a balloon to 15cm
- Data recorded in a table.
STEM teaching and learning activities
- Students explore and describe the reaction between bicarbonate of soda and vinegar. Encourage students to determine whether the amount of bicarbonate of soda affects the amount of gas formed.
- Challenge students to inflate a balloon to a height/circumference of 15cm.
- Students discuss how they can design a tool that will accurately and consistently measure the height or circumference of a balloon.
- Students make the measuring tool they have designed.
- Students will need to address a number of technical issues, such as how to:
- capture the gas
- measure the height or circumference of the balloon
- determine the amounts of bicarbonate of soda and vinegar
- transfer the bicarbonate into the vinegar without losing any gas.
- Students will need to address controlled variables to enable fair testing. These are:
- measuring quantities of bicarbonate of soda
- amount of vinegar in each attempt
- size of the bottle
- same brand and size of balloon. Students will need time to experiment with the reaction to determine the controls and also to devise an accurate way of measuring the height/circumference of the balloon.
- Create a table to document results. Students record the amount of bicarbonate of soda, volume of vinegar and the height/circumference of the balloon. Take photos of each attempt. Have students begin the experiment with 1 teaspoon of bicarbonate of soda and one quarter-cup of vinegar. Doubling the amount of bicarbonate of soda for each attempt. The amount of vinegar is kept constant to make this a fair test. As more vinegar and bicarbonate of soda are added the bottle becomes unstable, a container may be of use to keep the bottle standing.
- Students complete the experiment, documenting their results and refining their techniques. Photos of each attempt can be loaded into the table as evidence and will serve as a reminder of what happened at each attempt.
- Discuss the information collected. Did all groups obtain the same results? If not, why? What conclusions can we draw from this experiment? Discuss issues that arose and possible solutions.
Vocabulary list
Conclusion – an opinion or judgement based on evidence
Fair test – an investigation where one variable (the independent variable) is changed and all other conditions (controlled variables) are kept the same; what is measured or observed is referred to as the dependent variable
Hypothesis – a predictive statement that can be tested using a range of methods, most often associated with experimental procedure; can be supported or refuted by experiment
Irreversible reaction – a chemical process where different substances are formed
Key inquiry questions
How can you tell whether a reaction is reversible or irreversible?
A reaction is reversible if you can get the materials that have reacted (reactants) back after the reaction. The reaction of vinegar and bicarbonate of soda is irreversible. When these substances are mixed, a different substance, the gas carbon dioxide (CO2) is produced. This gas cannot be converted back to form vinegar and bicarbonate of soda, so this reaction is an irreversible reaction. When substances are mixed and a different substance is formed a chemical reaction has occurred. Chemical reactions are irreversible reactions.
What inflates the balloon?
When bicarbonate of soda and vinegar mix, a chemical reaction occurs and one of the products of this reaction is carbon dioxide gas. Carbon dioxide is made until there is either no vinegar or bicarbonate of soda left to react. So much gas is produced that it (and the air that was in the bottle) fills up the bottle and the balloon.
Why do we need to have control measures?
Students are developing the concept of a fair test and that factors may contribute to differing results, eg different-sized balloons. This means that results cannot be compared.
How can the height or circumference of a balloon be measured?
Balloons may inflate and deflate quickly and it may be difficult to capture a measurement. Shops that regularly inflate balloons (usually with helium) have a set of sizing templates. Students could easily make these.
Additional information
The following statements outline some common preconceived ideas that many students hold, which are scientifically inaccurate and may impede student understanding.
A change of state is a chemical reaction
The reaction of bicarbonate of soda (solid) with vinegar (liquid) produces carbon dioxide (gas). While the three states of matter are involved in this reaction this is not a change of state. Each of these substances is different. They each have a different chemical structure.
A change of state occurs when the same chemical substance, eg water, changes from the solid form (ice) to the liquid form (water) to the gaseous form (water vapour). This change usually depends on the energy (heat) available, and as heat is added or removed the state of matter changes. The change of state is a reversible reaction.
New substances are formed in chemical reactions
This statement is not entirely accurate. In the reaction between bicarbonate of soda and vinegar (acetic acid), carbon dioxide is generated. In this sense the carbon dioxide is a ‘new’ substance, but it comes from the vinegar and bicarbonate of soda.
The chemical reaction is symbolised as:
While this equation is far too complex for Stage 3, it shows that every atom present in the reactants is conserved and is present in the products of the reaction. In other words, the carbon dioxide formed, is not ‘new’; it is a recombination of atoms present in the bicarbonate of soda and vinegar.
Support materials
- Chemical reactions: teacher resource on critical teaching ideas about chemical reactions
- Balloon blowout
- Develop a Fair Test: Splash interactive
- Reversible and irreversible reactions: student interactive
Diversity of learners
For extension
- Research other chemical reactions that generate gases.
- Investigate the differences between reversible and irreversible reactions..
Review
By completing this STEM activity you have given your students opportunities to devise fair tests, gather and record data. Students use formal units of measurement in different ways and have discussed the importance of being accurate. They have created a tool that helps produce a standard product.
Students have investigated characteristics of chemical reactions. Understanding the characteristics of chemical reactions is essential in Science Stages 4 and 5 and Chemistry Stage 6.
NSW Government