Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 665 · 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.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) yeast (d) lemon juice
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
3. 3.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) lick your fingers (d) rub your eyes
4. 4.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) the paper floats (d) writing turns green
5. 5.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
6. 6.True or false: letting the paper dry is a job for an adult. (a) False (b) True
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
8. 8.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
9. 9.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
10. 10.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) writing the message
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) lemon juice (c) a cotton bud (d) white paper
12. 12.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
13. 13.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) cutting the lemon (d) ironing the paper
14. 14.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) putting the iron away (d) writing the message
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
17. 17.🔮 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
18. 18.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
19. 19.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is cold (d) it is magnetic
20. 20.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
21. 21.⚖️ 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) how dark the writing is
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
23. 23.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) lemon juice (d) turmeric powder
25. 25.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
26. 26.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) dipping the cotton bud
27. 27.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
28. 28.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) cutting the lemon (d) plugging in the iron
29. 29.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
30. 30.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
31. 31.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) a small bowl (d) a mirror
33. 33.⚖️ 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) the same cotton bud (c) how dark the writing is
34. 34.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
36. 36.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) ironing the paper (d) letting the paper dry
37. 37.True or false: cutting the lemon is a job for an adult. (a) False (b) True
38. 38.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) reading the message
39. 39.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) reading the message (d) putting the iron away
40. 40.True or false: putting the iron away is a job for an adult. (a) True (b) False

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