Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 831 · 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: white paper is not needed for the secret lemon message. (a) False (b) True
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) yeast (c) an adult with an iron (d) a small bowl
3. 3.⚖️ 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) True (b) False
4. 4.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) lemon juice (c) a balloon (d) a magnet
5. 5.⚖️ 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
6. 6.⚖️ 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
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) a balloon (d) lemon juice
9. 9.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) cutting the lemon (d) writing the message
10. 10.True or false: plugging in the iron is a job a child can do. (a) True (b) False
11. 11.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
12. 12.⚖️ 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 kind of juice (c) how dark the writing is (d) the same paper
13. 13.🔮 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
14. 14.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) the juice scorches first (d) heat adds colour
15. 15.True or false: writing the message is a job for an adult. (a) False (b) True
16. 16.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
18. 18.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) skip washing (d) rub your eyes
19. 19.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) reading the message (d) ironing the paper
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
21. 21.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
22. 22.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
23. 23.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) a battery cell (d) a small bowl
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
26. 26.True or false: ironing the paper is a job a child can do. (a) True (b) False
27. 27.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the same cotton bud (c) the same paper (d) the kind of juice
29. 29.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) musical (d) physical
30. 30.True or false: cutting the lemon is a job for an adult. (a) False (b) True
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
33. 33.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is sticky (d) it is cold
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) an adult with an iron (d) lemon juice
35. 35.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) white paper (c) an adult with an iron (d) a small bowl
37. 37.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
38. 38.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
39. 39.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) a small bowl (d) an adult with an iron

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