Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 924 · 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? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is (d) the same paper
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) True (b) False
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) the iron is brown (d) heat adds colour
6. 6.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
7. 7.True or false: ironing the paper is a job a child can do. (a) True (b) False
8. 8.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it can burn skin (d) it is sticky
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a mirror (c) yeast (d) a magnet
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) lemon juice (d) a balloon
11. 11.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
12. 12.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
13. 13.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) reading the message
14. 14.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) lemon juice (d) a magnet
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) a small bowl (d) white paper
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
18. 18.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a small bowl (c) lemon juice (d) an adult with an iron
20. 20.True or false: plugging in the iron is a job a child can do. (a) True (b) False
21. 21.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
22. 22.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) letting the paper dry
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) lemon juice (d) white paper
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) turmeric powder (c) white paper (d) an adult with an iron
25. 25.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) chemical (d) magnetic
26. 26.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) letting the paper dry
27. 27.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) yeast (d) white paper
29. 29.⚖️ 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) the same paper (c) how dark the writing is (d) the ironing time
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
31. 31.⚖️ 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
32. 32.True or false: white paper is needed for the secret lemon message. (a) False (b) True
33. 33.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) the paper ate it (d) dry juice is see-through
34. 34.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a battery cell (d) a cotton bud
37. 37.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
38. 38.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) cutting the lemon (d) putting the iron away
39. 39.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
40. 40.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) ironing the paper (d) putting the iron away

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