Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 352 · 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 yeast for the secret lemon message? (a) not needed (b) needed
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
4. 4.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) putting the iron away
5. 5.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) letting the paper dry (d) dipping the cotton bud
8. 8.⚖️ 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
9. 9.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) ironing the paper (d) dipping the cotton bud
10. 10.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
11. 11.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
12. 12.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
13. 13.True or false: white paper is needed for the secret lemon message. (a) True (b) False
14. 14.🔍 Which is the odd one out? (a) reading the message (b) cutting the lemon (c) ironing the paper (d) putting the iron away
15. 15.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) yes, if cooled (d) no, it stays brown
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) turmeric powder (c) a small bowl (d) a cotton bud
17. 17.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) any child (c) the youngest child (d) whoever is fastest
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a mirror (c) a small bowl (d) a cotton bud
19. 19.True or false: reading the message is a job for an adult. (a) False (b) True
20. 20.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
21. 21.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) putting the iron away (d) cutting the lemon
22. 22.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a mirror (c) a magnet (d) an adult with an iron
23. 23.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a balloon (c) lemon juice (d) an adult with an iron
25. 25.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) white paper (d) yeast
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) a cotton bud (d) a balloon
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) how dark the writing is (c) the iron setting (d) the ironing time
29. 29.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
30. 30.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
31. 31.⚖️ 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 measure it (c) we keep it the same
32. 32.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) plugging in the iron
33. 33.True or false: putting the iron away is a job a child can do. (a) True (b) False
34. 34.⚖️ 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 keep it the same (c) we measure it
35. 35.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) writing the message (c) dipping the cotton bud (d) letting the paper dry
36. 36.⚖️ 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) the same paper (c) how dark the writing is
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) white paper (d) lemon juice
38. 38.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
39. 39.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) putting the iron away
40. 40.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it

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