Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 92 · 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.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
2. 2.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
3. 3.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
4. 4.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
5. 5.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) reading the message
6. 6.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) an adult with an iron (d) a small bowl
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) an adult with an iron (c) lemon juice (d) a small bowl
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a small bowl (c) white paper (d) a mirror
11. 11.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) no, it stays brown (d) yes, if cooled
12. 12.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) writing the message
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a small bowl (d) turmeric powder
14. 14.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
15. 15.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
16. 16.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) writing the message (d) letting the paper dry
17. 17.⚖️ 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 measure it (c) we change it
18. 18.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a cotton bud (d) turmeric powder
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) lemon juice (d) a mirror
21. 21.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the paper ate it (c) the ink is magnetic (d) it turned into air
22. 22.⚖️ 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 measure it (c) we keep it the same
23. 23.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
24. 24.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
25. 25.⚖️ 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
26. 26.True or false: ironing the paper is a job a child can do. (a) True (b) False
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
28. 28.True or false: letting the paper dry is a job a child can do. (a) False (b) True
29. 29.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) how dark the writing is (c) the kind of juice (d) the iron setting
31. 31.⚖️ 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 paper (c) the kind of juice
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a small bowl (d) yeast
34. 34.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) letting the paper dry
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the iron setting (c) how dark the writing is (d) the ironing time
36. 36.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) plugging in the iron
37. 37.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) letting the paper dry (c) dipping the cotton bud (d) reading the message
38. 38.🔮 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
39. 39.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
40. 40.⚖️ 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

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