Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 14 · 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: a cotton bud is not needed for the secret lemon message. (a) True (b) False
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a battery cell (c) lemon juice (d) a cotton bud
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) white paper (d) a mirror
5. 5.⚖️ 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
6. 6.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
7. 7.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
8. 8.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) writing the message (d) plugging in the iron
9. 9.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) reading the message
10. 10.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) putting the iron away
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
12. 12.⚖️ 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 change it (c) we measure it
13. 13.🧺 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) turmeric powder
14. 14.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
15. 15.🍋 Which of these steps is a job for an adult? (a) writing the message (b) ironing the paper (c) reading the message (d) dipping the cotton bud
16. 16.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) an adult with an iron (d) a battery cell
19. 19.⚖️ 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
20. 20.True or false: reading the message is a job a child can do. (a) True (b) False
21. 21.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the kind of juice (c) the ironing time (d) how dark the writing is
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) yeast (d) a small bowl
24. 24.🔮 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
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
26. 26.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
27. 27.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) reading the message (c) dipping the cotton bud (d) writing the message
28. 28.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) reading the message
29. 29.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a magnet (d) white paper
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a mirror (d) lemon juice
32. 32.True or false: writing the message is a job for an adult. (a) False (b) True
33. 33.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) an adult with an iron (c) yeast (d) a battery cell
34. 34.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) dipping the cotton bud (d) putting the iron away
35. 35.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
37. 37.True or false: ironing the paper is a job a child can do. (a) True (b) False
38. 38.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) yeast (c) white paper (d) an adult with an iron
40. 40.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) heat adds colour (d) the iron is brown

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