Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 67 · 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.⚖️ 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 same cotton bud
2. 2.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a cotton bud (d) turmeric powder
5. 5.True or false: ironing the paper is a job a child can do. (a) True (b) False
6. 6.🍋 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) reading the message
7. 7.⚖️ 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
8. 8.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
9. 9.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) white paper (c) a cotton bud (d) an adult with an iron
11. 11.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) yeast (d) white paper
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the same cotton bud (c) the ironing time (d) the same paper
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a small bowl (d) a mirror
16. 16.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
17. 17.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) white paper (d) turmeric powder
18. 18.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
19. 19.True or false: letting the paper dry is a job a child can do. (a) False (b) True
20. 20.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
21. 21.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
22. 22.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) plugging in the iron (d) writing the message
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
24. 24.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
25. 25.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
26. 26.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
27. 27.True or false: putting the iron away is a job a child can do. (a) True (b) False
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
29. 29.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
30. 30.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) lemon juice (d) a balloon
31. 31.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
32. 32.⚖️ 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
33. 33.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a cotton bud (d) a balloon
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
36. 36.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) cutting the lemon (d) dipping the cotton bud
37. 37.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
38. 38.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
39. 39.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a small bowl (c) a balloon (d) turmeric powder
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True

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