Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 945 · 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.True or false: yeast is needed for the secret lemon message. (a) False (b) True
2. 2.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
3. 3.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) letting the paper dry (d) writing the message
4. 4.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
5. 5.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
6. 6.⚖️ 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) True (b) False
7. 7.⚖️ 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
8. 8.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) turmeric powder (c) a balloon (d) a battery cell
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we change it (c) we measure it
10. 10.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
12. 12.⚖️ 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
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the kind of juice (c) the ironing time (d) how dark the writing is
14. 14.⚖️ 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) the iron setting (c) how dark the writing is
15. 15.🔮 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
16. 16.⚖️ 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
17. 17.⚖️ 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 change it (c) we measure it
18. 18.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
19. 19.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
20. 20.⚖️ 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) the same paper (c) the iron setting (d) how dark the writing is
21. 21.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
22. 22.True or false: cutting the lemon is a job for an adult. (a) False (b) True
23. 23.🍋 Which of these steps is a job for an adult? (a) reading the message (b) putting the iron away (c) writing the message (d) dipping the cotton bud
24. 24.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) plugging in the iron (d) cutting the lemon
25. 25.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) a cotton bud (d) a battery cell
27. 27.⚖️ 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 same paper (c) the kind of juice
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) a magnet (d) yeast
29. 29.True or false: putting the iron away is a job a child can do. (a) False (b) True
30. 30.True or false: letting the paper dry is a job a child can do. (a) False (b) True
31. 31.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
32. 32.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
33. 33.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
34. 34.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
35. 35.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
36. 36.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) lemon juice (c) a cotton bud (d) a small bowl
38. 38.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
39. 39.🛟 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
40. 40.⚖️ 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 keep it the same (c) we change it

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