Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 851 · 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.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
2. 2.⚖️ 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) True (b) False
3. 3.⚖️ 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
4. 4.⚖️ 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 measure it (c) we change it
5. 5.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) dipping the cotton bud (d) letting the paper dry
6. 6.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) writing the message (d) ironing the paper
7. 7.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) plugging in the iron (d) cutting the lemon
8. 8.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
9. 9.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
10. 10.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
11. 11.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
12. 12.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) the juice scorches first (d) heat adds colour
13. 13.⚖️ 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
14. 14.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) a magnet (d) a balloon
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) yeast (d) an adult with an iron
17. 17.⚖️ 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
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
19. 19.True or false: putting the iron away is a job a child can do. (a) True (b) False
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
21. 21.True or false: cutting the lemon is a job for an adult. (a) True (b) False
22. 22.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a balloon (c) turmeric powder (d) a magnet
23. 23.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
24. 24.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) yeast (c) a small bowl (d) lemon juice
26. 26.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) a battery cell (d) an adult with an iron
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
29. 29.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) an adult with an iron (d) a mirror
31. 31.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
32. 32.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the ironing time
34. 34.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) turmeric powder (d) a balloon
36. 36.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) an adult with an iron (c) white paper (d) a small bowl
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same cotton bud (c) the kind of juice (d) how dark the writing is
39. 39.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
40. 40.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air

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