Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 100 · 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.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
2. 2.⚖️ 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
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) an adult with an iron (d) a battery cell
4. 4.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
5. 5.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
6. 6.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a balloon (d) a mirror
7. 7.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) white paper (d) a mirror
8. 8.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
9. 9.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) letting the paper dry (d) ironing the paper
10. 10.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
11. 11.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
12. 12.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
14. 14.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
15. 15.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) yeast (c) a mirror (d) a magnet
17. 17.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ 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
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a magnet (d) white paper
20. 20.True or false: writing the message is a job a child can do. (a) True (b) False
21. 21.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) cutting the lemon
22. 22.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
23. 23.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) ironing the paper (d) writing the message
24. 24.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) skip washing (d) wash your hands
25. 25.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
26. 26.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a cotton bud (c) lemon juice (d) a small bowl
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) the paper floats (d) writing turns green
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) magnetic (d) musical
29. 29.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
30. 30.True or false: putting the iron away is a job a child can do. (a) True (b) False
31. 31.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green
32. 32.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) dark brown words (d) a rainbow
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) white paper (d) a magnet
34. 34.⚖️ 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) the iron setting (c) how dark the writing is
35. 35.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) any child (c) the youngest child (d) whoever is fastest
36. 36.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) letting the paper dry (d) dipping the cotton bud
37. 37.🍋 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
38. 38.⚖️ 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 paper (d) the iron setting
39. 39.True or false: ironing the paper is a job for an adult. (a) True (b) False
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) yeast (d) a cotton bud

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