Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 308 · 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) the kind of juice (b) how dark the writing is (c) the same cotton bud (d) the ironing time
2. 2.⚖️ 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 change it (c) we measure it
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a mirror (c) white paper (d) an adult with an iron
4. 4.True or false: writing the message is a job a child can do. (a) False (b) True
5. 5.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
6. 6.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
7. 7.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) skip washing (c) rub your eyes (d) lick your fingers
9. 9.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
10. 10.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
11. 11.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
12. 12.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
13. 13.⚖️ 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 keep it the same (c) we change it
14. 14.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) turmeric powder (c) yeast (d) a battery cell
15. 15.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
16. 16.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) white paper (d) yeast
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it
18. 18.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
19. 19.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a balloon (d) lemon juice
20. 20.🔮 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
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) yeast (c) an adult with an iron (d) a cotton bud
23. 23.⚖️ 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 keep it the same (c) we measure it
24. 24.🍋 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
25. 25.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) writing the message
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a cotton bud (d) a battery cell
27. 27.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
28. 28.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
29. 29.True or false: reading the message is a job for an adult. (a) True (b) False
30. 30.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) white paper (c) a mirror (d) a balloon
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) turmeric powder (d) a cotton bud
32. 32.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) turmeric powder (d) a battery cell
34. 34.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) writing the message (d) putting the iron away
35. 35.⚖️ 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
36. 36.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
37. 37.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
39. 39.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
40. 40.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed

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