Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 300 · 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 kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
3. 3.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
4. 4.True or false: white paper is needed for the secret lemon message. (a) False (b) True
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) the iron is brown (d) paper turns lemony
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a balloon (d) lemon juice
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) a small bowl (c) a cotton bud (d) white paper
8. 8.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) lemon juice (d) a magnet
11. 11.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
12. 12.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a mirror (c) a magnet (d) a balloon
13. 13.⚖️ 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
14. 14.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) letting the paper dry
15. 15.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
16. 16.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
17. 17.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
18. 18.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) writing the message (c) ironing the paper (d) putting the iron away
19. 19.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) reading the message (d) ironing the paper
20. 20.⚖️ 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
21. 21.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) writing the message (d) reading the message
22. 22.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
23. 23.🛟 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
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
25. 25.True or false: reading the message is a job a child can do. (a) False (b) True
26. 26.True or false: writing the message is a job for an adult. (a) True (b) False
27. 27.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) whoever is fastest (d) any child
29. 29.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) ironing the paper (d) plugging in the iron
30. 30.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
32. 32.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
33. 33.True or false: ironing the paper is a job a child can do. (a) True (b) False
34. 34.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if cooled (d) yes, if shaken
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a small bowl (d) a magnet
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) how dark the writing is (c) the kind of juice (d) the iron setting
37. 37.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
38. 38.⚖️ 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
39. 39.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) reading the message (c) plugging in the iron (d) cutting the lemon
40. 40.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing

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