Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 219 · 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: plugging in the iron is a job a child can do. (a) False (b) True
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a cotton bud (d) yeast
3. 3.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
4. 4.True or false: reading the message is a job a child can do. (a) True (b) False
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) a magnet (d) lemon juice
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
7. 7.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) a battery cell (d) white paper
8. 8.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) writing the message (d) letting the paper dry
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we keep it the same (c) we change it
10. 10.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) turmeric powder (c) lemon juice (d) a cotton bud
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) lemon juice (c) white paper (d) a cotton bud
13. 13.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the iron setting
15. 15.⚖️ 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) True (b) False
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) a balloon
17. 17.True or false: letting the paper dry is a job for an adult. (a) True (b) False
18. 18.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) white paper (d) a mirror
20. 20.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
21. 21.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
22. 22.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) the same cotton bud (d) the same paper
24. 24.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) writing the message (d) putting the iron away
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) the same cotton bud (d) how dark the writing is
26. 26.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
27. 27.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) skip washing (d) wash your hands
28. 28.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
29. 29.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) writing stays faint (d) the paper floats
30. 30.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
31. 31.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
32. 32.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) an adult with an iron (d) a cotton bud
34. 34.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
36. 36.True or false: ironing the paper is a job a child can do. (a) True (b) False
37. 37.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
39. 39.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
40. 40.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green

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