Invisible Ink Experiment Worksheet

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

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