Balloons

Balloons

Pencil and paper
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about observing the changes that happen when a balloon is heated in water
a)
Your teacher will be demonstrating a science investigation.
Complete this worksheet for the activity.
 
Prediction
Draw what the bottle and balloon will look like after the water has been heated.
Explanation
Explain why you think the balloon and bottle will look the way you have drawn them.
Observation
Draw a labelled diagram showing what you observed when the water was heated.
Explanation
Add to or change your ideas about why it happened.

b)
 
Sam and Hiria were investigating what happens to the size of a blown-up balloon when it is put in hot and cold places.
 
  i)
Will the balloon get bigger or smaller or stay the same size when it is put in a freezer?
 
bigger / smaller / stay the same size  (Circle one)
 
  ii)
Will the balloon get bigger or smaller or stay the same size when it is put in a warm place in the sun? 
 
bigger / smaller / stay the same size  (Circle one)
Task administration: 
This task can be completed with pencil and paper and other equipment.
 
Equipment:
a balloon; a narrow necked bottle; a pot of water; a heat source, e.g., electric element.
 
In the task, the teacher demonstrates the activity.
  • Begin the POE activity by establishing what is in the bottle (air).
  • Pull the balloon over the neck of the bottle. Tell the students you are going to stand the bottle in the pot and heat the water.
  • Ask the students to draw on the worksheet the shape of the balloon and bottle when the water has heated, and write an explanation of why they think this.
  • Heat the water. Students observe what happens.
  • Ask students to draw exactly what they see, with annotations. Add to or change their explanations in light of the observation.
  • Have students debate their ideas. This could lead to further investigations to test their science ideas.
  • Complete part b).

Level:
4
Curriculum info: 
Science, Investigating in science, Material World
Keywords: 
properties, gas, air, heat, predict-observe-explain
Description of task: 
Task: Predict, Observe, Explain, (POE) activity observing what happens to air in a balloon when it is heated. Assessment focus: behaviour of gases when heated and cooled.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
 
Capability: Gather and interpret data
This resource provides opportunities to discuss describing being about what you see, and explaining being about what your observations make you think.
 

 
Science capabilities: 
Gather and interpret data
Answers/responses: 

a)

i)

Prediction: Any prediction.

  

ii)

 What you look for
Do students' explanations include any or all of the following?

  • Air is a gas;
  • Air/gas is made up of particles/molecules;
  • When air/gas is heated it takes up more space/expands;
  • Air/gas takes up more space when heated because the particles move further apart/move around more/faster;
  • Because the air/gas takes up more space, it exerts pressure on the inside of the balloon, and so inflates it.
 

   

iii)
   ______   
 

The balloon gradually fills up with air and stands up.
  

iv)

Have students made any additions or alterations to their initial explanation that attempts to explain what they observed? (Refer to a) ii) for specific details.)

b)

i)
ii)

get smaller
get bigger
Diagnostic and formative information: 
  • Balloons are a useful context for investigating air, because they provide visual clues about an invisible substance.
  • Use the answer guide to identify possible gaps in students' understanding, and plan activities that extend and challenge the students' current ideas.

Knowledge about gases
The trial students gave some interesting reasons for incorrectly predicting that a balloon would get bigger when stored in a fridge.

Student's explanation

Knowledge base used by student

Scientific explanation

Water increases in size and has a bigger mass when it freezes.

Incorrectly applying knowledge of water turning to ice.

Water is unusual in that it takes up more space when it freezes. Most materials, including air, take up less space when they get cold, because the molecules get closer together.
The plastic will get weaker and air will escape. Observation of balloons over a period of time. Air does gradually escape, but over a longer period of time. The observation is unrelated to the temperature of the air in the balloon.

Measurement
Originally for this task the students were asked to measure a blown up balloon, and then predict what would happen if a) it was put in a cold place, and b) it was put in a hot place.
The trial students all predicted the balloon would get bigger when it was cold (see Knowledge about gases above). Because their measurement strategies were not precise, and the variations in size were small, the students unconsciously made their measurements "fit" their predictions. The amended task eliminates the measuring problem, and is more visual, but still explores the same concept.
 
Building Science Concepts
Ministry of Education (2003). Building Science Concept Book 30, The air around us. Wellington: Learning Media.