Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 976 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical
2. 2.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
3. 3.True or false: yeast is needed for the secret lemon message. (a) False (b) True
4. 4.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
5. 5.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
6. 6.⚖️ 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 measure it (c) we change it
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) an adult with an iron (c) a cotton bud (d) lemon juice
8. 8.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
9. 9.⚖️ 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 keep it the same (c) we measure it
10. 10.⚖️ 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
11. 11.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) letting the paper dry
12. 12.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a magnet (d) a small bowl
14. 14.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
15. 15.⚖️ 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
16. 16.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud (d) the same paper
18. 18.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) reading the message
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a mirror (c) an adult with an iron (d) a cotton bud
20. 20.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
21. 21.🍋 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
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) turmeric powder (d) lemon juice
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) an adult with an iron (d) lemon juice
24. 24.True or false: putting the iron away is a job a child can do. (a) True (b) False
25. 25.True or false: writing the message is a job a child can do. (a) True (b) False
26. 26.True or false: ironing the paper is a job a child can do. (a) False (b) True
27. 27.🍋 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
28. 28.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) turmeric powder (d) yeast
29. 29.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
30. 30.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
31. 31.⚖️ 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 change it (c) we keep it the same
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
33. 33.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
34. 34.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) dipping the cotton bud (d) reading the message
35. 35.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) turmeric powder (d) a cotton bud
38. 38.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
40. 40.True or false: plugging in the iron is a job for an adult. (a) False (b) True

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