Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 409 · 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.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) putting the iron away (d) dipping the cotton bud
2. 2.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) lemon juice (d) yeast
4. 4.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) almost nothing (d) blue words
5. 5.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) it gets darker (d) writing turns green
7. 7.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
8. 8.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
10. 10.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
11. 11.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) letting the paper dry
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a small bowl (c) a cotton bud (d) white paper
13. 13.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
14. 14.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
15. 15.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
16. 16.True or false: white paper is needed for the secret lemon message. (a) True (b) False
17. 17.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, if shaken (d) yes, in the dark
18. 18.⚖️ 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 keep it the same (c) we measure it
19. 19.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
21. 21.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) the iron is brown (d) heat adds colour
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) turmeric powder (b) lemon juice (c) a cotton bud (d) a small bowl
23. 23.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
24. 24.⚖️ 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 same paper
25. 25.⚖️ 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 same cotton bud (c) the ironing time (d) the kind of juice
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
27. 27.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) writing the message
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) white paper (c) a balloon (d) a mirror
29. 29.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) a balloon (d) a cotton bud
31. 31.⚖️ 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) how dark the writing is (c) the iron setting
32. 32.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is cold (d) it is magnetic
33. 33.⚖️ 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 ironing time
34. 34.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
35. 35.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) letting the paper dry (d) plugging in the iron
36. 36.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) a balloon (d) an adult with an iron
37. 37.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) putting the iron away (d) cutting the lemon
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
39. 39.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child

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