Fizzy bubbly science - ABC (Australian Broadcasting Corporation)

[Pages:10]Fizzy bubbly science

Brief description

Students observe the chemical reaction between vinegar (an acid) and sodium bicarbonate (a base). In small groups, they observe how bubbles of carbon dioxide gas produced by this reaction cause popcorn kernels to float and sink in water. They blow soap bubbles, which float on an invisible layer of carbon dioxide inside a soft drink bottle. As an optional extension activity, they can make fizzy edible sherbet.

Duration: Year Level: Topics:

Preparation: Extensions:

60 ? 80 minutes

Lower to upper primary

Chemical reactions, Acids and Bases, Liquids & Gases, Floating & sinking, Buoyancy, Density

15 minutes

SCIENCE ? Make sherbet (included in student worksheet) SCIENCE ? Research carbon dioxide (eg composition of the Earth's atmosphere, sources of CO2, pollution, greenhouse effect) ART/SCIENCE ? Construct an erupting model volcano with play-dough or paper mache

Overview

Whole class

Small groups Whole class

Teacher demonstration Discuss procedure and safety instructions Designate group work jobs

Activity 1 ? Make and investigate pop-corn lava lamp Activity 2 ? Floating bubbles Discuss activities Plan next science lesson

(5 ? 10 min)

(30 ? 45 min) (5 ? 10 min)

Materials and equipment

NOTE: Two 500g packets of Sodium Bicarbonate (baking soda) and one 2 litre bottle of vinegar should be sufficient for all the activities and teacher demonstration combined.

Teacher Demonstration

Total Qty

Description

1

390 or 600 ml soft drink bottle

1

Balloon

1

Funnel *

3

Tbsp sodium bicarbonate

?

Cup vinegar

* cut the top off a soft drink bottle to make a funnel if necessary

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Materials and Equipment continued ...

Total Qty

Description

30 18 6 6 6 6 1 packet 2 ? 500 g 2 litre

75g 2 packets

student worksheets

3 pages ? download separately and photocopy

Clear plastic cups and/or glasses 1 litre soft drink bottles (tops cut off)1 Small bubble blowers and solution 2 Tablespoons Teaspoons Un-cooked pop corn Sodium bicarbonate Vinegar Water

Sherbet ingredients and materials Citric Acid 3 Flavoured jelly crystals 4

(1 per student)

(1 per group) (1 per group) (1 per group) (1 per group) (1 per group) (1 tbsp / group) ( ? cup / group) (1 cup / group) (1 cup / group)

1 packet

Pure icing sugar

6 1 ? 6

30

Small plastic bowls or plates Sieve(s) Small plastic bags or similar to store sherbet

1 cut tops off with a utility knife prior to the lesson 2 students may be able to bring this item from home or you can make them easily ? alternatively,

`wedding bubbles' are readily available from most supermarkets including solution and blower 3 available in baking section at supermarkets 4 note: jelly crystals are not suitable for vegetarians

Preparation

Materials for teacher to collect:

y Sufficient quantities of plastic cups, bubble mix and blowers, popping corn, vinegar and sodium bicarbonate (bi-carb soda), spoons

y Download and photocopy 30 student worksheets y Making sherbet: citric acid, flavoured jelly crystals, icing sugar, bowls, sieve(s)

Materials for students to collect:

y Empty 1 litre soft-drink bottles (minimum of 6 required for lesson) y If available at home ? small bubble blower and solution

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Objectives

You should check the outcomes statement for the year level of your class before deciding which of the following objectives are appropriate.

Accurately describing and explaining the observations in these activities requires the synthesis of several scientific concepts. This may take different amounts of time for individual students. Asking questions about each concept in isolation may help students arrive at the correct explanation for their observations.

Students' prior knowledge

Students are familiar with their group work job responsibilities.

No prior knowledge of scientific concepts is assumed for this lesson.

Positive attitudes

Students will: y work cooperatively in small groups y ensure each member has an opportunity to see and understand the activities y handle equipment and materials carefully and responsibly y use water sparingly and dispose of waste responsibly (eg pour onto school garden beds, not into sinks)

Science skills

Popcorn Lava Lamp Activity

Students will:

y follow the instructions accurately y measure the required amounts of sodium bicarbonate and

vinegar y observe the formation of carbon dioxide bubbles in the solution

y observe that these bubbles adhere to the popcorn pieces

y observe that the popcorn pieces float when covered with bubbles

y observe that the bubbles pop when the popcorn reaches the surface, causing the pop corn to rotate

y observe that the popcorn sinks after the bubbles have popped y describe their observations in writing and with illustrations

Catch-A-Bubble Activity

Students will:

y follow the instructions accurately y measure the required amounts of sodium bicarbonate and

vinegar y carefully blow bubbles and gently move the bottle to catch them y observe that the bubbles float on the invisible layer of carbon

dioxide y infer that carbon dioxide is a heavier (more dense) gas than air

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Objectives continued ...

Science concepts

y vinegar is a type of acid y sodium bicarbonate is a type of base y acids and bases undergo a chemical reaction when mixed

together y one of the products of the vinegar and sodium bicarbonate

reaction is a gas called carbon dioxide y carbon dioxide gas is less dense than water (it floats in water) y popcorn kernels are more dense than water (they sink in water) y air is less dense than carbon dioxide gas ? air floats on carbon

dioxide / carbon dioxide sinks in air

Procedure

Introduction (Whole class / 5 ? 10 min)

y Perform the teacher demonstration (see teacher notes on page 5) y Discuss the activities and give instructions for how you expect students to collect

materials from the science store to prevent spills, you may wish to distribute the vinegar and sodium bicarbonate to each work station once the groups have collected all the other materials and are ready to begin y Allocate group work jobs and badges

Hands-on activities (Small groups / 30 ? 45 min)

Small group activities

y All group members cooperate to prepare a work station y All group members read the worksheet instructions y Equipment Managers collect materials required from Science Store

f

y Group Communication Officer asks teacher to deliver vinegar and sodium bicarbonate to work station (if not collected by Equipment Managers)

y Group Supervisors ensure group adheres to instructions and completes activities y Records Officers keep careful notes of results where necessary y Equipment Managers clean and return equipment to the Science Store y Remainder of group cleans Work Station and returns desks to normal locations

Early finishers

y These activities are fun and visually stimulating so early finishers are likely to enjoy extra time to repeat the activities

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Conclusion (Whole class / 10 ? 15 min)

Class discussion

y Conduct a discussion about the activities

Plan next science lesson

y Ask students to collect and bring in any household items you might require for the next lesson you have planned

Teacher notes

Teacher demonstration

This demonstration will engage and motivate students. It provides clear visual evidence that gas is produced when vinegar and sodium bicarbonate react. Because students enjoy watching experiments, you can perform the entire set up (i.e. filling the balloon and bottle) as part of the demonstration.

1. Pour ? a cup of vinegar into the empty soft-drink bottle using a funnel 2. Pour 1? tablespoons of sodium bicarbonate into the uninflated balloon 3. Carefully stretch the mouth of the balloon over the mouth of the bottle making sure

the sodium bicarbonate stays in the balloon 4. Lift and shake the balloon so that all the sodium bicarbonate pours into the bottle

and let go of the balloon ? the balloon will quickly inflate with carbon dioxide gas produced by the reaction

Before ingredients are mixed

After ingredients are mixed

Description of the chemical reaction

When an acid and a base react, they typically form a "salt" and water. In this reaction, vinegar is the acid (acetic acid) and sodium bicarbonate is the base. The products of the reaction are sodium acetate (the "salt"), water and carbonic dioxide. In chemical notation, the reaction is stated as:

HC2H3O2 + NaHCO3 ? NaC2H3O2 + H2O + CO2

Acetic Acid

+ Sodium

?

Bicarbonate

Sodium Acetate

+ Water + Carbon Dioxide

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Description of the popcorn motion

Popcorn kernels are only slightly more dense than water. The combination of a corn kernel and gas bubbles is less dense than water and therefore buoyant. When the reaction begins producing carbon dioxide bubbles, the kernels start to float. Once the corn reaches the surface, the bubbles at the top of the kernel burst. The bubbles attached to the bottom of the kernel now cause it to rotate. Once these remaining bubbles have burst, the kernel sinks again and the process is repeated. The diagram below illustrates the motion of a corn kernel.

3. Bubbles on top of kernel pop

4. Kernel spins, remaining bubbles pop

` 2. Bubbles make the kernel

float

5. After bubbles have popped, kernel sinks

1. Bubbles form on kernel

6. Process starts again

Motion of a popcorn kernel

Catch-A-Bubble: why do the bubbles grow as they sink?

You may notice that the bubbles in this activity grow as they slowly sink further into the layer of carbon dioxide. This happens because the concentration of carbon dioxide is much greater outside than inside the bubble. Carbon dioxide is readily soluble in water and easily passes through the bubble solution (which is mainly water) and into the bubble. Air (mainly nitrogen and oxygen) however, is not as readily soluble in water. The bubble expands and becomes heavier as carbon dioxide enters, causing it to sink slowly further down into the bottle.

Bubble floating on carbon dioxide in a coffee plunger glass

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Solutions to common problems

Popcorn Lava Lamp

Bubbles are forming but popcorn isn't moving: Wait a little longer. If the popcorn still isn't moving after about two minutes, add more sodium bicarbonate and/or vinegar.

Catch-A-Bubble

Bubbles aren't floating: Possibly because the bottle is being moved too quickly or students are breathing directly into it, either of which may expel the carbon dioxide. Add more vinegar and/or sodium bicarbonate being careful not to breath into the bottle. Move the bottle gently.

Sherbet extension activity

The fizzing sensation experienced when eating sherbet is a result of the chemical reaction between the citric acid and sodium bicarbonate. This reaction also produces small bubbles of carbon dioxide but only when the dry ingredients are wet by saliva in the mouth.

NOTE: the recipe provided contains jelly crystals, which are not suitable for vegetarians ? exclude the jelly crystals if required

Carbon dioxide in the Earth's atmosphere

The Earth's atmosphere consists mainly of nitrogen (78%) and oxygen (21%), and a small amount of trace gases. The amount of carbon dioxide varies slightly due to human activities and natural causes but forms roughly 0.036% of the atmosphere.

The trace gases include: argon (0.93%) neon (0.0018%) helium (0.0005%) hydrogen (0.00005%)

Oxygen (21%)

Trace gases including carbon dioxide (1%)

Nitrogen (78%)

Composition of Earth's Atmosphere

Source: Commonwealth Department of the Environment and Heritage

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.

Fizzy bubbly science

Name ______________________________________

Materials required per group:

1 plastic cup filled with water

1 measuring spoon

1 tablespoon of popcorn

? cup of vinegar (in a plastic cup)

1 empty soft-drink bottle (top removed) 1 bubble blower and solution

8 tablespoons of baking soda (in a plastic cup)

Activity 1: Popcorn Lava Lamp

Introduction

In this activity, you will mix baking soda and vinegar in water. Amazing things will happen when the bubbles of carbon dioxide begin to form. Watch the popcorn carefully and try to explain your observations in the space provided.

Procedure

1. Add one tablespoon of baking soda to the water and stir thoroughly. Wait till the mixture goes clear. 2. Add six or eight pieces of popcorn. 3. Add three tablespoons of vinegar to the water and watch carefully ? it might take up to a minute or two

before things begin to happen. If nothing happens after two minutes, ask the teacher for assistance.

Record your observations

1. Describe what is happening to the popcorn kernels in your cup. Think about the following questions to help with your explanation: Do popcorn kernels usually float? Why? What happens to the bubbles when they reach the surface? What do the popcorn kernels do at the surface? Why?

Fizzy bubble science ? Student Worksheet

ABC Science Online ( .au/science )

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