Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 768 · 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: putting the iron away is a job a child can do. (a) True (b) False
2. 2.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
3. 3.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
4. 4.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
5. 5.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) it gets darker (d) writing turns green
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) an adult with an iron (d) a small bowl
8. 8.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
9. 9.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
10. 10.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
11. 11.⚖️ 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
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) turmeric powder (c) white paper (d) a small bowl
13. 13.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) letting the paper dry (d) putting the iron away
14. 14.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
15. 15.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) yeast (d) a small bowl
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) almost nothing (d) blue words
18. 18.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
19. 19.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) reading the message (d) putting the iron away
20. 20.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
21. 21.🔮 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
22. 22.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
23. 23.True or false: white paper is needed for the secret lemon message. (a) False (b) True
24. 24.⚖️ 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
25. 25.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) writing the message (c) reading the message (d) dipping the cotton bud
26. 26.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
27. 27.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
28. 28.True or false: plugging in the iron is a job a child can do. (a) False (b) True
29. 29.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) reading the message (c) putting the iron away (d) cutting the lemon
30. 30.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
31. 31.True or false: turmeric powder 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.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
34. 34.True or false: cutting the lemon is a job a child can do. (a) True (b) False
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same paper (c) the ironing time (d) the iron setting
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) turmeric powder (d) lemon juice
38. 38.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
39. 39.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) letting the paper dry (d) putting the iron away
40. 40.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True

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