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Alex

Plant's Secret Weapon

Slip a plastic bag over a leafy branch, seal it tight, and leave it in the sun. A few hours later — water appears inside a bag that started completely dry. Where did it come from?

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Ages

7-12 yrs

Duration

min
10

Difficulty

Easy

Stage

Stage 2-3

Cite this resource 

Created by Darin Carr (BSc, DipEd)
NESA Accredited Teacher · Chemistry & Physics Specialist · 30+ years in-class teaching
Resource Version: 1.0
First Published: 

Last Updated: 

22 June 2026
21 Aug 2026
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MISSION VERIFIED

Classroom tested. Teacher designed. Safe at home.

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Designed by Darin Carr (BScDip Ed)

Practising NESA accredited

Australian Science Teacher

★ 30+ years of classroom experience

MISSION PROGRESS

1

young scientists have completed this mission.

I'VE COMPLETED THIS MISSION

Click to let us know you have completed this mission

LATEST TEACHER FEEDBACK

No feedback yet for this experiment. Use it with your class and let us know how it went!

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Before you investigate... watch the mystery

MISSION HOOK

Professor Picklebottom and the team are travelling and collecting amazing science mysteries.

✔ Coming in Term 1 2027

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Mission Equipment

Gather your materials and get

ready for an amazing mission!

  • 1 leafy plant (indoor houseplant or outdoor bush/tree branch)

  • 1 clear plastic bag (sandwich bag or ziplock)

  • 1 rubber band or twist tie

  • A kitchen measuring cup or jug (with mL markings)

  • String or masking tape (optional — for extra seal)

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Let’s Investigate

Follow the missions steps below to solve the mystery.

1

Choose your plant

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  • Pick a healthy, leafy plant — a leafy indoor houseplant or an outdoor bush or tree works perfectly. 

  • The more leaves you can fit inside your bag, the better your result.

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

2

Set. the trap!

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  • Slip your clear plastic bag over a cluster of leaves — aim for as many leaves as will comfortably fit. 

  • Push the bag down so the leaves sit deep inside, then squeeze the open end around the stem and seal it tight with your rubber band

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

3

Check your starting point

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  • Before you walk away, look inside the bag. Is it completely clear and dry? Good — you're ready.

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

4

Leave it in the sun

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  • Put your plant in a sunny spot and leave the bag on for at least 2 hours. 

  • Outdoors in direct sunlight gives the fastest and most dramatic result. 

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

5

Collect & Measure

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  • Carefully peel off the rubber band and remove the bag over your measuring cup. 

  • Tilt the bag so all the collected water runs into the cup, then read the measurement. 

  • Even 1–2 mL means the experiment worked perfectly — that water came entirely from inside the plant.

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1

Big Title

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1

Big Title

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1

Big Title

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

Gather your materials and get

ready for an amazing mission!

1

Big Title

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

1

Choose your plant

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

1

Choose your plant

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

1

Big Title

Snail Slime step 2.jpg

Gather your materials and get

ready for an amazing mission!

PREDICT

OBSERVE

EVIDENCE

ASK

SAFETY

TIP

PREDICT

The Crazy Scientist LAB Learning System™

Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.

We

  • LINK to what they already know,

  • ACTIVATE curiosity through hands-on discovery

  • BUILD understanding that actually sticks.

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You already know plants need water to survive — you water them, they grow, easy. But here's something almost nobody knows: 

  • plants don't just drink water. They release it. Every single day, through millions of tiny holes you can't even see.

Here's the challenge: can you catch the water that your plant is secretly releasing — using nothing but a plastic bag?


Make your prediction.


 How much water do you think your plant will release in two hours?

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  • The bag was sealed the whole time — so where did the water come from? Nothing could get in from outside.

  •  Do you think a plant with more leaves would give you more water, or the same amount? What's your reasoning?

  • If you hadn't put the bag there, where would that water have ended up?x

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Plants release water through tiny holes in their leaves — that's called transpiration.


  • You're stranded on a deserted island. A person needs about 2 litres of water per day to survive. How many bags, on how many plants, would you need to stay alive?

  • Why would a leafy tree in full sunlight give you more water than the same tree in deep shade?

  • On a hot, humid day the air feels heavy with moisture — how does transpiration from millions of plants connect to that feeling?

"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."

Think Like a Scientist

Scientists don't stop after their first discovery.

They ask new questions, collect more evidence and test their ideas in different ways.

Where could you take this investigation next?

What happens if you put your bag in full sunlight instead of shade — does the plant release more water?

What happens if you use a plant with bigger, broader leaves — does leaf size change how much water you collect?

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Dr Puddledrip’s Science Tip
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 Read the Science

Every leaf on every plant is covered in thousands of tiny pores called stomata — far too small to see without a microscope, but they're there on almost every leaf. 


When you sealed the bag around the leaves, any water vapour from the plant leaf had nowhere to go. It hit the cooler surface of the plastic and turned back into liquid water — the same process that makes a cold glass go wet on the outside on a hot day. 


That change from vapour back to liquid is called condensation.


Here's the survival science — and this part is real:

  • In wilderness survival situations, people wrap clear bags around leafy branches in full sun to collect clean, drinkable water. It's called a transpiration bag, and survival guides teach it as a genuine emergency water-collection technique. You just built one.

Think of it like this: every time you walk past a garden on a hot day and feel that cool, slightly humid air — that's transpiration at work. The plants are sharing their water with the atmosphere.



Curiosity spark: Scientists estimate the Amazon rainforest releases about 20 billion tonnes of water into the atmosphere every single day through transpiration. That water forms clouds, falls as rain, and keeps the entire region alive. 


What do you think happens to the rainforest's climate if the trees are cut down?

Teachers & Homeschoolers: Print-ready HD versions of this Science Behind It poster and companion G&T Challenge Card are available inside The Crazy Scientist LAB.

Scientist's Challenge

Designed for HPGE, gifted learners and children who enjoy an extra challenge.

Teachers & Homeschoolers: Print-ready HD versions of this Science Behind It poster and companion G&T Challenge Card are available inside The Crazy Scientist LAB.

The Next Question...

You've solved today's mystery. Now discover where curiosity can take you next.

Teachers & Homeschoolers: Print-ready HD versions of this Science Behind It poster and companion G&T Challenge Card are available inside The Crazy Scientist LAB.

Vocabulary

Transpiration — The loss of water vapour from a plant’s leaves.


Stomata — Tiny openings in leaves that allow gases and water vapour to move in and out.


Water Vapour — Water in its invisible gas form.

Know a parent or teacher who'd love this? Send it on! 👇

Keep Exploring This Mystery

One experiment leads to even more amazing discoveries inside the Learning Universe.

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READY TO TEACH THIS
TOMORROW?

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Running the experiment is easy; however, teaching it well is another challenge.

Teachers often ask:

How do I adapt this for Stages 1,2 or 3?

What misconceptions will they have?

What syllabus outcomes does it cover?

What do I do with fast finishers?

How do I structure this for a full class?

What do I say when they ask WHY?

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