Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 406 · 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.⚖️ 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) False (b) True
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a small bowl (d) turmeric powder
3. 3.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) putting the iron away
4. 4.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
5. 5.⚖️ 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 iron setting (c) how dark the writing is
6. 6.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
7. 7.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) a cotton bud (d) a mirror
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a mirror (d) a cotton bud
9. 9.⚖️ 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
10. 10.⚖️ 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 same paper (c) how dark the writing is (d) the kind of juice
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) a small bowl (d) a mirror
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
13. 13.🔮 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
14. 14.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
15. 15.True or false: yeast is needed for the secret lemon message. (a) True (b) False
16. 16.🛟 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
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) lemon juice (d) a small bowl
18. 18.⚖️ 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
19. 19.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing turns green (d) writing stays faint
21. 21.True or false: plugging in the iron is a job for an adult. (a) False (b) True
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) a mirror
23. 23.⚖️ 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
24. 24.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) rub your eyes (d) skip washing
26. 26.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
27. 27.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
28. 28.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) letting the paper dry (d) cutting the lemon
29. 29.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the ironing time
31. 31.⚖️ 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
32. 32.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) white paper (c) a magnet (d) turmeric powder
34. 34.⚖️ 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
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a balloon (d) lemon juice
36. 36.True or false: writing the message is a job a child can do. (a) False (b) True
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) turmeric powder (b) a small bowl (c) an adult with an iron (d) lemon juice
38. 38.⚖️ 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 change it (c) we keep it the same
39. 39.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
40. 40.⚖️ 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

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