Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 505 · 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 battery cell is needed for the secret lemon message. (a) False (b) True
2. 2.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
3. 3.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
4. 4.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) plugging in the iron (c) ironing the paper (d) cutting the lemon
5. 5.⚖️ 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 same cotton bud (c) the kind of juice (d) how dark the writing is
6. 6.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) reading the message (c) letting the paper dry (d) writing the message
7. 7.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) turmeric powder (c) a magnet (d) yeast
8. 8.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
9. 9.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
10. 10.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) lemon juice (d) white paper
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
14. 14.⚖️ 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 keep it the same (c) we change it
15. 15.🧺 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) turmeric powder (d) a small bowl
16. 16.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
18. 18.⚖️ 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
19. 19.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
22. 22.⚖️ 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) True (b) False
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
24. 24.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the ironing time (d) the kind of juice
26. 26.True or false: cutting the lemon is a job for an adult. (a) True (b) False
27. 27.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) turmeric powder (c) a magnet (d) a mirror
28. 28.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
29. 29.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
30. 30.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
31. 31.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) no, it stays brown (d) yes, if cooled
32. 32.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a mirror (c) a balloon (d) a battery cell
33. 33.True or false: letting the paper dry is a job for an adult. (a) True (b) False
34. 34.🍋 Which of these steps is a job a child can do? (a) writing the message (b) ironing the paper (c) putting the iron away (d) cutting the lemon
35. 35.⚖️ 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 same cotton bud (c) how dark the writing is
36. 36.🍋 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
37. 37.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) reading the message (d) dipping the cotton bud
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) yeast (d) a cotton bud
39. 39.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
40. 40.⚖️ 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

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