Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 499 · 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: a magnet is needed for the secret lemon message. (a) True (b) False
2. 2.⚖️ 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 paper (c) how dark the writing is (d) the same cotton bud
3. 3.True or false: cutting the lemon is a job a child can do. (a) True (b) False
4. 4.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
6. 6.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) letting the paper dry
7. 7.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is sticky (d) it is magnetic
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) lemon juice (d) a battery cell
9. 9.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
10. 10.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
12. 12.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) lemon juice (c) a magnet (d) a battery cell
15. 15.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
16. 16.True or false: ironing the paper is a job a child can do. (a) True (b) False
17. 17.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
19. 19.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) writing the message (d) putting the iron away
20. 20.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) an adult with an iron (d) a balloon
22. 22.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
23. 23.⚖️ 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
24. 24.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
25. 25.⚖️ 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
26. 26.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
27. 27.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
28. 28.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) lemon juice (d) a magnet
30. 30.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) yeast (d) a mirror
33. 33.⚖️ 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
34. 34.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
35. 35.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
36. 36.True or false: cutting the lemon is a job for an adult. (a) True (b) False
37. 37.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
38. 38.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) dipping the cotton bud (d) ironing the paper
39. 39.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child

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