Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 808 · 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.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) white paper (d) a battery cell
2. 2.⚖️ 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
3. 3.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
4. 4.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
5. 5.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
7. 7.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
8. 8.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) plugging in the iron (d) dipping the cotton bud
9. 9.⚖️ 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
10. 10.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
11. 11.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) putting the iron away (d) dipping the cotton bud
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a magnet (c) white paper (d) a small bowl
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
14. 14.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) writing the message
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) the same paper (c) the iron setting (d) how dark the writing is
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same paper (c) the same cotton bud (d) the kind of juice
17. 17.True or false: letting the paper dry is a job a child can do. (a) True (b) False
18. 18.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
19. 19.True or false: yeast is needed for the secret lemon message. (a) False (b) True
20. 20.⚖️ 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 keep it the same (c) we change it
21. 21.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
22. 22.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) cutting the lemon (c) reading the message (d) letting the paper dry
23. 23.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) a balloon (d) lemon juice
26. 26.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
27. 27.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
28. 28.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
29. 29.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a battery cell (d) a balloon
30. 30.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) putting the iron away
31. 31.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) writing the message (c) cutting the lemon (d) putting the iron away
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) an adult with an iron (d) yeast
33. 33.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
34. 34.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
35. 35.🧺 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) a cotton bud
36. 36.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
37. 37.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
38. 38.🛟 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
39. 39.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
40. 40.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed

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