Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 793 · 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 is the odd one out? (a) plugging in the iron (b) ironing the paper (c) dipping the cotton bud (d) putting the iron away
2. 2.⚖️ 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 change it (c) we keep it the same
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) the same paper (d) how dark the writing is
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
5. 5.⚖️ 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
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) yeast (c) a mirror (d) a battery cell
7. 7.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
8. 8.True or false: plugging in the iron is a job a child can do. (a) True (b) False
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) white paper (d) a mirror
11. 11.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
12. 12.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
13. 13.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) letting the paper dry (d) putting the iron away
14. 14.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
15. 15.True or false: white paper is needed for the secret lemon message. (a) True (b) False
16. 16.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) letting the paper dry
17. 17.True or false: ironing the paper is a job for an adult. (a) False (b) True
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) yeast (d) an adult with an iron
19. 19.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
20. 20.⚖️ 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) False (b) True
21. 21.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) blue words (d) a rainbow
22. 22.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) reading the message (d) plugging in the iron
23. 23.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
24. 24.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
25. 25.🍋 Which of these steps is a job for an adult? (a) reading the message (b) plugging in the iron (c) letting the paper dry (d) writing the message
26. 26.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a cotton bud (d) a balloon
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
29. 29.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) turmeric powder (c) lemon juice (d) a cotton bud
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
31. 31.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
32. 32.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
33. 33.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) writing the message (d) cutting the lemon
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
35. 35.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
36. 36.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
38. 38.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) reading the message
39. 39.True or false: ironing the paper is a job a child can do. (a) True (b) False
40. 40.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical

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