Invisible Ink Experiment Worksheet

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

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