Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 222 · 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: a cotton bud is not needed for the secret lemon message. (a) True (b) False
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a magnet (c) an adult with an iron (d) lemon juice
3. 3.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) letting the paper dry (c) ironing the paper (d) plugging in the iron
4. 4.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) putting the iron away (d) plugging in the iron
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) blue words (d) dark brown words
7. 7.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) yeast (d) lemon juice
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
10. 10.⚖️ 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
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) lemon juice (d) a small bowl
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a small bowl (d) lemon juice
13. 13.True or false: letting the paper dry is a job for an adult. (a) False (b) True
14. 14.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) it turned into air (d) dry juice is see-through
15. 15.True or false: reading the message is a job for an adult. (a) False (b) True
16. 16.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a battery cell (c) a balloon (d) a magnet
17. 17.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) heat adds colour (d) the iron is brown
18. 18.True or false: plugging in the iron is a job a child can do. (a) False (b) True
19. 19.True or false: writing the message is a job a child can do. (a) False (b) True
20. 20.True or false: letting the paper dry is a job a child can do. (a) True (b) False
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) writing stays faint (d) the paper floats
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a mirror (d) an adult with an iron
23. 23.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
24. 24.🛟 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
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a small bowl (c) an adult with an iron (d) lemon juice
26. 26.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) plugging in the iron (c) dipping the cotton bud (d) writing the message
27. 27.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) a small bowl (d) a battery cell
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
29. 29.⚖️ 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 kind of juice (c) the iron setting
30. 30.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
31. 31.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
32. 32.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
33. 33.⚖️ 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) the kind of juice (c) the iron setting (d) the ironing time
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
35. 35.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it can burn skin (d) it is cold
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) white paper (d) turmeric powder
39. 39.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
40. 40.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False

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