Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 747 · 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? Which of these is the one thing we change? (a) how dark the writing is (b) the same paper (c) the kind of juice (d) the iron setting
2. 2.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
3. 3.True or false: cutting the lemon is a job a child can do. (a) True (b) False
4. 4.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) white paper (d) a battery cell
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a mirror (d) white paper
7. 7.True or false: plugging in the iron is a job for an adult. (a) True (b) False
8. 8.🍋 Which of these steps is a job for an adult? (a) writing the message (b) cutting the lemon (c) reading the message (d) letting the paper dry
9. 9.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) letting the paper dry
10. 10.True or false: putting the iron away is a job for an adult. (a) True (b) False
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) a cotton bud (d) a battery cell
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) lemon juice (d) a cotton bud
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) a balloon (d) a magnet
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
15. 15.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) whoever is fastest (d) the youngest child
16. 16.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) white paper (d) a battery cell
17. 17.True or false: white paper is needed for the secret lemon message. (a) True (b) False
18. 18.True or false: putting the iron away is a job a child can do. (a) True (b) False
19. 19.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) turmeric powder (b) lemon juice (c) a cotton bud (d) an adult with an iron
21. 21.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) yeast (d) a small bowl
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
24. 24.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
25. 25.⚖️ 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
26. 26.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) putting the iron away (d) letting the paper dry
27. 27.⚖️ 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) True (b) False
28. 28.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
29. 29.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
30. 30.True or false: cutting the lemon is a job for an adult. (a) False (b) True
31. 31.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
32. 32.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) writing the message (d) plugging in the iron
33. 33.⚖️ 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 change it (c) we keep it the same
34. 34.⚖️ 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
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) the kind of juice (c) how dark the writing is
36. 36.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
37. 37.🧺 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
38. 38.⚖️ 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
39. 39.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
40. 40.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) writing the message

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