Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 52 · 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.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
2. 2.⚖️ 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 kind of juice (d) the ironing time
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) lemon juice (c) a cotton bud (d) white paper
5. 5.⚖️ 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) False (b) True
6. 6.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) yes, if cooled (d) no, it stays brown
7. 7.🍋 Which of these steps is a job a child can do? (a) reading the message (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
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.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) white paper (d) a balloon
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
12. 12.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
13. 13.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) letting the paper dry (d) putting the iron away
14. 14.🧺 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 magnet
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) lemon juice (d) a cotton bud
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) yeast (c) a small bowl (d) white paper
17. 17.🔮 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
18. 18.⚖️ 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 iron setting
19. 19.⚖️ 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 ironing time (d) how dark the writing is
20. 20.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) putting the iron away (d) letting the paper dry
21. 21.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
22. 22.⚖️ 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
23. 23.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
25. 25.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
26. 26.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
27. 27.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
28. 28.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) the iron is brown (d) heat adds colour
29. 29.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) reading the message (d) ironing the paper
30. 30.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) blue words (d) a rainbow
31. 31.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
32. 32.⚖️ 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
33. 33.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
34. 34.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) ironing the paper
35. 35.True or false: yeast is needed for the secret lemon message. (a) False (b) True
36. 36.True or false: reading the message is a job a child can do. (a) True (b) False
37. 37.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) any child (d) whoever is fastest
38. 38.True or false: letting the paper dry is a job a child can do. (a) False (b) True
39. 39.⚖️ 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) False (b) True
40. 40.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True

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