Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 548 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) rub your eyes (d) wash your hands
3. 3.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
4. 4.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
5. 5.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
7. 7.🍋 Which of these steps is a job for an adult? (a) writing the message (b) ironing the paper (c) dipping the cotton bud (d) reading the message
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a battery cell (d) a cotton bud
9. 9.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
10. 10.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
11. 11.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) reading the message (d) ironing the paper
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
13. 13.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) a battery cell (d) white paper
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a balloon (c) white paper (d) lemon juice
15. 15.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) writing the message (d) putting the iron away
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a battery cell (d) a cotton bud
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
18. 18.True or false: plugging in the iron is a job for an adult. (a) False (b) True
19. 19.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) a rainbow (d) almost nothing
20. 20.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
21. 21.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) cutting the lemon
22. 22.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
23. 23.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
24. 24.True or false: ironing the paper is a job a child can do. (a) True (b) False
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
27. 27.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) turmeric powder (d) a small bowl
28. 28.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
29. 29.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the paper ate it (d) the ink is magnetic
30. 30.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a cotton bud (d) turmeric powder
32. 32.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) letting the paper dry (c) dipping the cotton bud (d) writing the message
33. 33.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) reading the message (d) cutting the lemon
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) an adult with an iron (d) a balloon
36. 36.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
38. 38.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) letting the paper dry (d) writing the message
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same cotton bud (c) the same paper (d) the ironing time
40. 40.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed

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