Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 418 · 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 kind of juice is kept the same. (a) True (b) False
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) lemon juice (d) yeast
4. 4.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) cutting the lemon (d) dipping the cotton bud
5. 5.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) a mirror (d) lemon juice
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a small bowl (d) turmeric powder
7. 7.🧺 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) a magnet
8. 8.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) cutting the lemon (c) writing the message (d) ironing the paper
9. 9.⚖️ 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
10. 10.🔮 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
11. 11.⚖️ 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
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
13. 13.True or false: putting the iron away is a job for an adult. (a) False (b) True
14. 14.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
15. 15.⚖️ 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
16. 16.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
17. 17.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
18. 18.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
19. 19.⚖️ 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 change it (c) we keep it the same
20. 20.🔮 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
21. 21.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) white paper (c) a small bowl (d) lemon juice
23. 23.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
24. 24.⚖️ 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
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) lemon juice (d) a balloon
26. 26.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
27. 27.True or false: writing the message is a job a child can do. (a) True (b) False
28. 28.⚖️ 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 iron setting (c) the ironing time (d) how dark the writing is
29. 29.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
30. 30.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) ironing the paper
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) white paper (d) yeast
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same cotton bud (c) the same paper (d) the kind of juice
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a balloon (c) a cotton bud (d) an adult with an iron
34. 34.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
35. 35.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) dipping the cotton bud (d) cutting the lemon
36. 36.⚖️ 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
37. 37.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
38. 38.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
39. 39.True or false: ironing the paper is a job for an adult. (a) False (b) True
40. 40.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) turmeric powder (d) a balloon

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