Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 332 · 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: a magnet is needed for the secret lemon message. (a) True (b) False
2. 2.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
3. 3.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
4. 4.🛟 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
5. 5.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) reading the message (d) letting the paper dry
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a balloon (d) an adult with an iron
7. 7.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) dark brown words (d) a rainbow
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
9. 9.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) cutting the lemon
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) lemon juice (d) a magnet
11. 11.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
12. 12.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) dipping the cotton bud (d) ironing the paper
13. 13.⚖️ 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 measure it (c) we keep it the same
14. 14.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
15. 15.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, in the dark (d) yes, if cooled
16. 16.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
17. 17.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
18. 18.True or false: writing the message is a job for an adult. (a) True (b) False
19. 19.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a cotton bud (d) a battery cell
21. 21.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
22. 22.⚖️ 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
23. 23.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a small bowl (d) turmeric powder
24. 24.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) ironing the paper (d) plugging in the iron
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
26. 26.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
27. 27.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
28. 28.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
29. 29.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
30. 30.🍋 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
31. 31.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) letting the paper dry (d) plugging in the iron
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a balloon (d) lemon juice
33. 33.True or false: white paper is needed for the secret lemon message. (a) False (b) True
34. 34.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) lemon juice (d) a magnet
35. 35.⚖️ 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) how dark the writing is (c) the same cotton bud (d) the iron setting
36. 36.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a cotton bud (d) turmeric powder
39. 39.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
40. 40.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True

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