Invisible Ink Experiment Worksheet

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

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