Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 623 · 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.⚖️ 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 keep it the same (c) we change it
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) turmeric powder (d) a small bowl
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) lemon juice (d) a small bowl
5. 5.True or false: yeast is needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) white paper (d) a small bowl
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the same cotton bud (c) the kind of juice
8. 8.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) it turned into air (d) the ink is magnetic
9. 9.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) chemical (c) physical (d) musical
10. 10.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) lemon juice (d) a mirror
12. 12.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) almost nothing (d) a rainbow
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same paper (c) how dark the writing is (d) the kind of juice
14. 14.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) putting the iron away (d) reading the message
15. 15.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
16. 16.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) reading the message (d) writing the message
17. 17.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
18. 18.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) reading the message
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
20. 20.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) writing the message (c) dipping the cotton bud (d) letting the paper dry
21. 21.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
23. 23.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
24. 24.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) reading the message (d) putting the iron away
25. 25.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
26. 26.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it is sticky (d) it can burn skin
27. 27.True or false: plugging in the iron is a job for an adult. (a) False (b) True
28. 28.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
29. 29.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
30. 30.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
31. 31.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a small bowl (d) a mirror
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
33. 33.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) lemon juice (d) an adult with an iron
35. 35.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
36. 36.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) white paper (d) a balloon
38. 38.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) putting the iron away (d) plugging in the iron
39. 39.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) paper turns lemony (d) the iron is brown
40. 40.⚖️ 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

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