Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 681 · 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.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) turmeric powder (d) lemon juice
3. 3.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
4. 4.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
5. 5.⚖️ 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 same cotton bud (c) how dark the writing is (d) the same paper
6. 6.⚖️ 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) the iron setting
7. 7.⚖️ 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
8. 8.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
9. 9.⚖️ 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 measure it (c) we keep it the same
10. 10.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) lemon juice (d) a balloon
12. 12.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
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 keep it the same (c) we measure it
14. 14.🧺 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) a mirror (d) a small bowl
15. 15.⚖️ 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 paper (c) how dark the writing is
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a small bowl (c) a mirror (d) a battery cell
17. 17.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
18. 18.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
19. 19.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) reading the message
20. 20.🔮 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
21. 21.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) no, it stays brown (d) yes, if cooled
22. 22.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
23. 23.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) lemon juice (d) a small bowl
26. 26.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) cutting the lemon (d) putting the iron away
27. 27.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) writing the message (d) ironing the paper
28. 28.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
29. 29.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) a small bowl (d) lemon juice
31. 31.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
32. 32.True or false: cutting the lemon is a job a child can do. (a) False (b) True
33. 33.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) lemon juice (d) a cotton bud
35. 35.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
36. 36.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
37. 37.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) putting the iron away
38. 38.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
39. 39.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) writing the message (d) ironing the paper
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same

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