Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 866 · 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.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) heat adds colour (d) paper turns lemony
2. 2.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
3. 3.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
4. 4.⚖️ 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 cotton bud
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a balloon (d) white paper
6. 6.⚖️ 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
7. 7.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
8. 8.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) an adult with an iron (c) a magnet (d) yeast
10. 10.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
11. 11.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
12. 12.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
13. 13.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) dipping the cotton bud
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a small bowl (c) a magnet (d) yeast
15. 15.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) blue words (d) dark brown words
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
17. 17.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) reading the message (d) cutting the lemon
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a mirror (d) a cotton bud
19. 19.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
20. 20.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
21. 21.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
22. 22.⚖️ 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) the iron setting (c) the same paper (d) how dark the writing is
23. 23.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a magnet (c) a battery cell (d) yeast
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) turmeric powder (c) lemon juice (d) a small bowl
25. 25.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) cutting the lemon (d) ironing the paper
26. 26.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) whoever is fastest (d) the youngest child
27. 27.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
28. 28.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) green (d) brown
29. 29.⚖️ 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
30. 30.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
31. 31.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a mirror (c) a balloon (d) turmeric powder
33. 33.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
34. 34.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
35. 35.True or false: writing the message is a job for an adult. (a) True (b) False
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
37. 37.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) writing the message (d) reading the message
38. 38.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
39. 39.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
40. 40.True or false: yeast is needed for the secret lemon message. (a) True (b) False

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