Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 360 · 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 is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) dipping the cotton bud (d) writing the message
2. 2.⚖️ 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
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) the ironing time (d) how dark the writing is
4. 4.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) cutting the lemon
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a balloon (d) white paper
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
7. 7.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
8. 8.⚖️ 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 iron setting (d) how dark the writing is
9. 9.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
10. 10.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
11. 11.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
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 of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) a magnet (d) white paper
14. 14.⚖️ 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
15. 15.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
16. 16.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) cutting the lemon (d) dipping the cotton bud
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
18. 18.True or false: writing the message is a job for an adult. (a) False (b) True
19. 19.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
20. 20.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
21. 21.True or false: letting the paper dry is a job a child can do. (a) True (b) False
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a cotton bud (d) a balloon
23. 23.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
24. 24.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
25. 25.True or false: ironing the paper is a job a child can do. (a) True (b) False
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) lemon juice (d) turmeric powder
27. 27.⚖️ 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) True (b) False
28. 28.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
29. 29.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ 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
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) a small bowl (d) lemon juice
32. 32.True or false: putting the iron away is a job for an adult. (a) False (b) True
33. 33.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
34. 34.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
35. 35.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) white paper (d) a magnet
36. 36.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
37. 37.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) putting the iron away (d) reading the message
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a small bowl (d) lemon juice
39. 39.True or false: putting the iron away is a job a child can do. (a) False (b) True
40. 40.🍋 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) reading the message

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