Throwing balloons 4
Equipment:
A water-filled balloon inside an air-filled balloon (see instructions below) for each group of students; a task (POE) sheet for each student.
Instructions for assembling balloon
It is easy to get water everywhere, so we suggest that you prepare the balloons ahead.
- Push one balloon inside another, keeping the nozzle of the inner balloon just above the outer balloon's nozzle, i.e., don't let it drop inside.
- Attach the inner balloon nozzle to a cold tap. Add water. Hold nozzle tightly, remove from the tap, and tie a knot in it. Note that the pressure from the uninflated outer balloon will force the water out at speed if you are not careful. The more water you put into the balloon the harder it is to manage.
- Push the tied-off water-filled balloon into the outer balloon.
- Blow up the outer balloon and tie off.
What to do
The task could be carried out in a number of ways. For example, you might decide to work in small groups or with the whole class. You might want to provide more or less scaffolding than we did. You may want students to respond orally to the Predict, Observe, Explain (POE) questions rather than filling in the sheet, especially if you just want to get a feel for where the class is, rather than individual students.
The instructions below are how we trialled the task.
- Give each student a copy of the POE sheet.
- Show students the balloon and what is inside it.
- Tell students they are going to make a prediction about what will happen when the balloon is thrown and then to explain why they have made this prediction. Ask them to fill in the first two sections of the sheet. Tell them not to discuss their ideas yet (but they will get a chance to share their ideas). Turn their sheets face down when they have finished.
- Ask three or four students to share their predictions and explanations, but don’t comment.
- Tell students that they will be working in small groups to investigate their predictions. They will need to observe carefully all that happens, and be thinking about why.
- Ask each group to form a circle, give each group a balloon and ask them to throw the balloon around the group. Give them a few minutes to explore.
- Ask students to fill in the last two boxes of the POE sheet. Explain that you are interested in what they think now compared to when they made their prediction.
- Collect the sheets.
Warning: The flight of the balloon is unpredictable. If you have access to a large indoor area, students could carry out the throwing activity there. However, the trial students safely managed this activity standing around their desks and throwing across and round them. If you are really worried about control (of the balloon or the class!) you could have a demonstration group, but this is not as engaging for those who just watch.
There are no right or wrong answers to this task. The table provides some things to look for in students' responses.
| a) | Makes a prediction. |
| b) |
Appropriately uses their current personal science understandings and/or experiences to justify their prediction. Look for evidence that the prediction is not just a random guess. |
| c) |
Accurately describes events that occurred.
|
| d) |
Adds to or changes their explanation based on what they observed or Adds to or changes their explanation based on both what they observed and in response to hearing others' explanations. |
For more specific details:
In Working with students, Diagnostic and formative information discusses common predictions, observations and explanations made by the trial students.
Both the Nature of Science focus and the science concepts are discussed.
Background information
This task was developed alongside a writing task, Balloon throwing II.
The intention of having two parallel tasks is to model a way of addressing two different assessment purposes within the same context.
Why are the ideas in this activity important?
Backing up statements with evidence is a feature of science explanations. This science task is about how students use their science knowledge to inform their predictions and explain their observations. The focus is on students' ideas. Children's explanations also provide teachers with data for deciding what science concepts to explore further.
Careful observation provides a rich basis for beginning to form explanations. In this context at Level 4 we would expect them to:
- Notice what the balloon does in different situations and make links between the structure of the balloon and how it moves.
- Mostly use everyday language to explain their ideas, but increasingly include some scientific vocabulary.
An understanding of forces is central to understanding the physical world. The context of the weighted balloon is in itself not of earth-shattering importance. However, the activity is very engaging because the balloon does surprising things, and it opens up all sorts of possibilities to explore a number of ideas about forces and motion.
At Level 4 students are expected to identify and describe the effects of forces (contact and non-contact) on the motion of objects (The New Zealand Curriculum). These ideas are typically explored in simple systems where the results are reasonably predictable. In the context of the wobbly balloon, which is a complex system, multiple explanations drawing on several science ideas are possible.
The key ideas covered in this task are shown in the following table.
| Nature of science idea | Science knowledge |
|
Understanding about science
|
Physical concepts
There are many science ideas that could be explored but the most likely at this level are:
|
The complexity of the science involved in the activity
This simple activity is very complex to explain, because there are so many different things happening. The balloon within a balloon is a complex little system where a number of things interact in different ways to affect the way it travels through the air. These interactions include:
- Collisions between the inner and outer balloons
- Shifting centre of gravity as the inner balloon moves in relation to the outer balloon
- The interaction of different forces, including pushes, air resistance and gravity
- The different speeds the two balloons travel.
Some of the things the students may notice are:
- The balloon travels faster and sometimes further than a normal air-filled balloon.
- The balloon drops faster than a normal air-filled balloon.
- Getting the inner balloon spinning or moving before throwing affects the balloon's trajectory.
- When the balloon is thrown the small water-filled balloon travels in the direction thrown. The air filled balloon rotates around it.
Nature of science: Supporting ideas with evidence
This section discusses the nature of science features of the task.
The first part of the POE task (the prediction and first explanation) provides evidence of students' initial ideas. The second explanation shows how (or if) students are refining their ideas in light of the observations they carried out. It is also interesting if you carry out the writing task, Balloon throwing II, to notice if students' explanations change again as they incorporate others' ideas. This building on of ideas demonstrates aspects of both individual thinking and collaborative endeavour, both of which are important in science.
Predicting
While predicting is not an assessment focus of this task, their predictions do provide some insight into students' initial thinking and therefore what changes occur as they interact with the activity and share ideas.
All of the trial students were able to make a prediction that was relevant to the described scenario. Most recognised that the balloon inside would impact on the way the balloon travelled – at Years 3 and 4 very few made this link. However, nearly half of them still made links to what they had experienced with ordinary balloons, most commonly making predictions about whether or not either of the balloons would pop.
Some students were quite definite about their prediction.
- It will drop and pop.
- It won't go very high.
- They will float for a bit then they will fall. (The ones with more water will fall sooner.)
Others were more tentative, which suggests they may have been trying to apply existing knowledge to a new situation, but were aware they might not have had all the pieces they needed.
- I think it might drop and wobble.
- I think the balloon with water will bounce around inside and the air filled balloon will drop quickly.
- It might fall.
The following table gives a broad pattern of predictions and the number of trial students' responses that were in each category (a few students' predictions fell into more than one category).
| Category of prediction | Number of students |
| No prediction/ prediction doesn't make sense | 0 |
| Prediction based on personal experiences with balloons (e.g., it will pop/not pop, float) | 13 |
| Prediction that the balloon will drop as opposed to float | 16 |
| Prediction focused on movement of water-filled balloon within the balloon (e.g., it will move around inside) | 3 |
| Prediction about the flight of the balloon, for example: It won't go very far. It will travel faster than a normal balloon. | 5 |
Based on a sample of 29 Year 7 and Year 8 students in November 2010
Describing observations
All students in the trial described something relevant they observed. Twelve of the twenty nine students described more than one thing they noticed (at Years 3-6 most students described just one thing they saw). Three included descriptions about what was happening both inside the balloon and the way it travelled.
This facility to notice more details is important, because it enabled students to make more connections in their explanations (see later discussion).
Many of the students commented later on whether their predictions were correct or incorrect, treating their second explanation as a critique of or reflection on their first ideas. Some just commented that they were right or wrong, but others provided evidence of changes to their thinking.
- Prediction: It won't go very far.
- 1 st explanation: It might not be very heavy.
- 2 nd explanation: I was wrong because it was quite heavy and went far when you throw it. Why? There was a heavier balloon on the inside.
This was in contrast to the Level 2 and 3 trials in which the students mainly just explained their observations without reference to their initial ideas.
Explaining predictions and observations
Most of the trial students were able to give explanations to support their predictions, although fewer were able to explain their observations.
Most students used everyday language to explain their ideas, even when they were explaining reasonably complex science.
- Because the balloon on the inside was heavier it travels faster and pushed the balloon on the outside causing the outside one to wobble.
- It wobbles because the balloon was tossing against the sides causing it to go in that direction.
However, a few included scientific vocabulary, generally demonstrating experimentation with using scientific words and beginning understandings rather than a scientifically correct understanding of the concepts.
- The force wasn't enough to pop the balloon.
- Because when you throw it the water balloon will go to the front and the inertia will be strongest.
- The balloon probably sped up whilst going down not only because of basic gravity, but because of weight at the bottom of the balloon because of inertia.
- It wobbled because there was a displacement of gravity.
Science knowledge
Six students explained their predictions by referring to previous experiences of balloons (most of these predicted that the balloon would pop).
cos it's getting thrown around a lot
It is interesting that thirteen students made predictions related to popping, but about half of these students drew on science ideas in their explanations. This is in contrast to Level 2 and 3 trial students who mostly just drew on their experiences.
After their observation all but one included more scientific ideas in their explanations about the flight of the balloon.
The trial students used three main science ideas to explain the predicted and observed flight of the balloon.
Weight
- My findings – the balloons together actually spinned or wobbled from the weight … cool!
- Because the balloon inside will make it heavy because it has water inside.
- Because the water weighed it down, so it fell quicker.
Momentum
None used this term – generally they discussed how fast it went.
The water was making it go faster.
Centre of gravity
While the students didn't use this term, some of them showed they had the beginnings of this concept by thinking about both the weight and the position or movement of the inner balloon.
- When the water weight moves it creates a big impact which makes it wobble.
- When we threw the balloon the water balloon inside moved forward and that's what made it move faster and wobble.
The table below shows the numbers of students giving explanations within the different categories for the first and second explanations. Note that students at this level sometimes gave answers that included ideas from more than one category, showing an awareness of the interactions between different parts of the balloon. These students were difficult to categorise so were credited with the concept that seemed they were drawing on most. However, a discussion with them would possibly show more awareness of the different interactions they noticed.
| Explanation 1 (explaining prediction) | Explanation 2 (explainingobservation) | |
| No explanation (in some cases more description) | 1 | 7 |
| Explanation related to previous experience of balloons (described above) | 6 | 1 |
| Explanations relating to pressure (to explain why it would pop) | 3 | 2 |
| Explanation related to weight | 15 | 9 |
| Explanations related to momentum | 3 | 1 |
| Explanation relating to centre of gravity (weight and position/movement of inner balloon) | 1 | 9 |
Overall after the observation there was a general movement towards using more complex science ideas in their explanations. Some students used the same idea but added to their explanation the second time. A few students were unable or did not attempt to explain their observations although they could give an explanation for their predictions. We wondered if they did not have sufficient experiences or science understandings to explain what they saw.
Key competencies
- Relating to others – listening to and responding to others' ideas
- Thinking – using ideas and experiences to think with.
Nature of science: Supporting ideas with evidence
Explanations
Encourage students to always explain their thinking. Some things you could be looking for are:
- Do they propose explanations?
- Do they use words such as maybe or a tentative tone to when proposing ideas? (This suggests they are trying to make meaning themselves.)
- Do they support their explanations with evidence?
- What sort of evidence do they draw on (books, observations, things seen on tv, what adults have told them, etc.)?
- Do they use cause and effect words such as because, as, since? (Do they realise explanations try to answer why something happens?)
- Do they use phrases such as it depends and if… then …(conditional thinking)?
- Do they use analogies to explain their ideas?
- Introduce appropriate vocabulary after students have explained the concept with some understanding.
- If students use a science word ask them to explain what they mean. Check that they are using the word appropriately.
- Quick games of various sorts, e.g., matching words with definitions, Loopy , can be useful for developing vocabulary,
Science knowledge
Students could carry out further investigations about the balloon and try to explain what happens.
Questions that the trial students were interested in included:
- What would happen if we threw it high?
- What if we could tie the balloon filled with water to a string so it hung in the middle of the other balloon?
- What if the balloon popped?
- What if we filled it with a different liquid?
- What if we filled the inside balloon with helium?
- What happens if we roll it?
For an analysis of a similar task carried out by Level 2 students go to Throwing balloons 2
For an analysis of the same task carried out by Level 4 students go to Throwing balloons 3
For the English writing resource that goes with this science task go to Balloon throwing II
For other ARB resources about:
Explanations, use the keyword explanations.
Flight, use the keywords parachutes.
Motion of liquid-filled objects, go to Cat food and soup,
Centre of gravity, use the keyword centre of gravity.
The following teaching resources provide ideas for further activities:
- Ministry of Education (2003). Building Science Concepts Book 34, Parachutes. Wellington: Learning Media. This book provides suggestions for further explorations about floating and falling in air. The concept overview and Science notes for teachers are helpful for understanding the way different forces interact.
- Ministry of Education (2003). Building Science Concepts Book 51, Standing up. Wellington: Learning Media. This book addresses some simple ideas about centre of gravity in structures, plants and animals. Look especially at Section Four.
- Ministry of Education (1999). Making Better Sense of the Physical World. Wellington: Learning Media. See the chapter, Force and Motion.
For more information about the Predict, Observe, Explain strategy and ARB resources that use it go to Assessment Strategies: Predict, Observe, Explain.
References
Bull, A., Joyce, C., Spiller, L. and Hipkins, R. (2010). Kick-starting the Nature of Science. Wellington: NZCER Press.