Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 712 · 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: turmeric powder is not needed for the secret lemon message. (a) True (b) False
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
3. 3.🔮 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
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) False (b) True
5. 5.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
6. 6.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
7. 7.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
8. 8.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
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 keep it the same (b) we change it (c) we measure it
10. 10.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
11. 11.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
13. 13.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
14. 14.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) plugging in the iron
15. 15.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) putting the iron away
16. 16.⚖️ 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
17. 17.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) dry juice is see-through (d) the paper ate it
18. 18.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) ironing the paper (d) putting the iron away
19. 19.True or false: ironing the paper is a job for an adult. (a) True (b) False
20. 20.⚖️ 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
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a balloon (d) a cotton bud
23. 23.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) the juice scorches first (d) heat adds colour
24. 24.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) writing the message (d) putting the iron away
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) an adult with an iron (d) a small bowl
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
27. 27.True or false: a small bowl is needed for the secret lemon message. (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 kind of juice (b) how dark the writing is (c) the same cotton bud (d) the same paper
29. 29.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) reading the message (d) ironing the paper
30. 30.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
31. 31.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
32. 32.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
33. 33.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it can burn skin (d) it is sticky
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) a cotton bud (d) an adult with an iron
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) white paper (d) a balloon
36. 36.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) reading the message
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) a battery cell (d) white paper
38. 38.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
39. 39.True or false: white paper is needed for the secret lemon message. (a) True (b) False
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult

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