Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 621 · 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: letting the paper dry is a job for an adult. (a) True (b) False
2. 2.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
3. 3.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
4. 4.True or false: putting the iron away is a job for an adult. (a) True (b) False
5. 5.🛟 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
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) white paper (d) lemon juice
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
8. 8.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) turmeric powder (d) a small bowl
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) lemon juice (c) an adult with an iron (d) a small bowl
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
12. 12.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) white (d) green
13. 13.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) reading the message (d) plugging in the iron
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a mirror (d) an adult with an iron
15. 15.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
16. 16.🍋 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
17. 17.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) letting the paper dry (d) reading the message
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 same cotton bud
19. 19.🔮 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
20. 20.🔍 Which is the odd one out? (a) letting the paper dry (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
21. 21.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
22. 22.⚖️ 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
23. 23.⚖️ 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) the iron setting
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) a cotton bud (d) white paper
25. 25.⚖️ 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 measure it (c) we keep it the same
26. 26.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
27. 27.True or false: reading the message is a job a child can do. (a) False (b) True
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) the same cotton bud (d) how dark the writing is
29. 29.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) reading the message (d) cutting the lemon
30. 30.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
31. 31.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) dipping the cotton bud (d) ironing the paper
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 measure it (b) we keep it the same (c) we change it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) lemon juice (d) a small bowl
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
35. 35.🧺 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) a cotton bud (d) a magnet
36. 36.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
37. 37.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) letting the paper dry
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
39. 39.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a battery cell (c) lemon juice (d) turmeric powder
40. 40.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True

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