Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 618 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) white paper (d) a small bowl
2. 2.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
3. 3.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
4. 4.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
5. 5.True or false: white paper is needed for the secret lemon message. (a) True (b) False
6. 6.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) musical (d) physical
7. 7.🔍 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
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same paper (d) the ironing time
9. 9.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
10. 10.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) ironing the paper (d) plugging in the iron
11. 11.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
12. 12.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
13. 13.⚖️ 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
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) lemon juice (d) white paper
15. 15.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
16. 16.🍋 Which of these steps is a job a child can do? (a) writing the message (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
17. 17.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
18. 18.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
19. 19.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) letting the paper dry (c) ironing the paper (d) plugging in the iron
20. 20.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a balloon (c) a magnet (d) yeast
21. 21.True or false: plugging in the iron is a job for an adult. (a) False (b) True
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a cotton bud (c) an adult with an iron (d) a small bowl
23. 23.True or false: plugging in the iron is a job a child can do. (a) True (b) False
24. 24.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
25. 25.True or false: cutting the lemon is a job for an adult. (a) False (b) True
26. 26.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) dry juice is see-through (d) the paper ate it
27. 27.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
28. 28.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
29. 29.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
30. 30.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
31. 31.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
32. 32.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) a balloon (d) white paper
33. 33.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
34. 34.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
35. 35.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
36. 36.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
38. 38.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) putting the iron away (d) letting the paper dry
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same paper (c) the kind of juice (d) the iron setting
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True

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