Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 228 · 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.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
3. 3.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
4. 4.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
6. 6.True or false: plugging in the iron is a job for an adult. (a) True (b) False
7. 7.True or false: cutting the lemon is a job a child can do. (a) False (b) True
8. 8.True or false: ironing the paper is a job a child can do. (a) False (b) True
9. 9.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) lemon juice (d) yeast
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 change it (b) we measure it (c) we keep it the same
12. 12.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a cotton bud (d) yeast
14. 14.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
15. 15.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) how dark the writing is (c) the iron setting (d) the same paper
17. 17.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) reading the message (d) cutting the lemon
18. 18.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
19. 19.🔮 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
20. 20.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
21. 21.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) dry juice is see-through (d) it turned into air
22. 22.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
23. 23.⚖️ 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 keep it the same (c) we measure it
24. 24.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
25. 25.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) writing the message
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) a balloon (d) lemon juice
27. 27.🍋 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
28. 28.⚖️ 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 measure it (c) we change it
29. 29.⚖️ 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
30. 30.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) an adult with an iron (c) a mirror (d) yeast
31. 31.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) reading the message (d) cutting the lemon
32. 32.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) white paper (d) yeast
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it
34. 34.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
35. 35.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
36. 36.True or false: white paper is needed for the secret lemon message. (a) False (b) True
37. 37.True or false: reading the message is a job a child can do. (a) True (b) False
38. 38.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) ironing the paper (d) cutting the lemon
39. 39.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) ironing the paper (d) reading the message
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) any child (d) only an adult

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