Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 190 · 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: white paper is needed for the secret lemon message. (a) True (b) False
2. 2.🔍 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
3. 3.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
4. 4.⚖️ 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
5. 5.True or false: yeast is needed for the secret lemon message. (a) True (b) False
6. 6.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) white paper (c) a cotton bud (d) a small bowl
8. 8.True or false: cutting the lemon is a job for an adult. (a) True (b) False
9. 9.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
10. 10.⚖️ 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
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) white paper (d) a mirror
12. 12.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
14. 14.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a magnet (d) an adult with an iron
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
18. 18.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
19. 19.True or false: cutting the lemon is a job a child can do. (a) True (b) False
20. 20.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) plugging in the iron (d) letting the paper dry
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) yeast (d) a battery cell
22. 22.🍋 Which of these steps is a job a child can do? (a) writing the message (b) ironing the paper (c) putting the iron away (d) cutting the lemon
23. 23.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) letting the paper dry (d) cutting the lemon
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the ironing time (c) how dark the writing is (d) the iron setting
25. 25.⚖️ 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
26. 26.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
27. 27.⚖️ 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
28. 28.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) ironing the paper (d) reading the message
29. 29.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) any child (d) whoever is fastest
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
31. 31.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) writing the message (d) dipping the cotton bud
32. 32.True or false: letting the paper dry is a job for an adult. (a) True (b) False
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a small bowl (d) turmeric powder
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
35. 35.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
36. 36.True or false: reading the message is a job for an adult. (a) True (b) False
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) yeast (d) white paper
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) white paper (d) lemon juice
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) yeast (c) a cotton bud (d) lemon juice
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False

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