Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 68 · 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) letting the paper dry (b) plugging in the iron (c) reading the message (d) dipping the cotton bud
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
3. 3.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
4. 4.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) it gets darker (d) the paper floats
6. 6.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
7. 7.True or false: putting the iron away is a job for an adult. (a) True (b) False
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a cotton bud (d) yeast
11. 11.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
12. 12.⚖️ 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
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) yeast (d) a magnet
14. 14.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) letting the paper dry
15. 15.True or false: reading the message is a job for an adult. (a) True (b) False
16. 16.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
17. 17.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) dipping the cotton bud (d) plugging in the iron
18. 18.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
19. 19.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
20. 20.⚖️ 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 ironing time (d) the iron setting
21. 21.True or false: putting the iron away is a job a child can do. (a) False (b) True
22. 22.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
23. 23.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) only an adult (d) any child
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) lemon juice (d) yeast
25. 25.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) writing the message
26. 26.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) writing the message
27. 27.⚖️ 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 keep it the same (c) we measure it
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
29. 29.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) ironing the paper (d) putting the iron away
30. 30.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
31. 31.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) reading the message (d) plugging in the iron
32. 32.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
34. 34.True or false: plugging in the iron is a job a child can do. (a) False (b) True
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
36. 36.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
37. 37.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
38. 38.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) turmeric powder (d) a small bowl
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True

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