Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 204 · 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.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
2. 2.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) a small bowl (d) a battery cell
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) an adult with an iron (d) a battery cell
5. 5.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) reading the message (d) ironing the paper
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
7. 7.⚖️ 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
8. 8.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
9. 9.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
10. 10.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) no, it stays brown (d) yes, if cooled
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) turmeric powder (c) an adult with an iron (d) a cotton bud
13. 13.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
16. 16.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
18. 18.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) a mirror (d) a cotton bud
19. 19.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
20. 20.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
21. 21.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) white paper (d) a mirror
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
24. 24.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
26. 26.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
27. 27.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) it gets darker (d) the paper floats
29. 29.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) writing the message (d) reading the message
30. 30.⚖️ 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
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) an adult with an iron (d) a mirror
32. 32.⚖️ 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
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the ironing time (c) how dark the writing is (d) the kind of juice
34. 34.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) lemon juice (d) a balloon
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) lemon juice (d) turmeric powder
37. 37.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
38. 38.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
39. 39.True or false: reading the message is a job for an adult. (a) False (b) True
40. 40.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) reading the message

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