Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 909 · 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 same cotton bud (b) the kind of juice (c) how dark the writing is (d) the same paper
2. 2.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
4. 4.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
5. 5.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
6. 6.True or false: reading the message is a job for an adult. (a) True (b) False
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) the iron is brown (d) paper turns lemony
8. 8.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
9. 9.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) reading the message
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) an adult with an iron (c) lemon juice (d) a cotton bud
11. 11.🛟 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
12. 12.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
13. 13.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) writing the message
14. 14.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
15. 15.⚖️ 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
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) lemon juice (c) a cotton bud (d) white paper
17. 17.⚖️ 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 keep it the same (c) we measure it
18. 18.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
19. 19.True or false: letting the paper dry is a job a child can do. (a) True (b) False
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) a cotton bud (d) a small bowl
21. 21.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a magnet (d) yeast
22. 22.⚖️ 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
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the kind of juice (c) how dark the writing is (d) the same paper
24. 24.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) letting the paper dry (c) plugging in the iron (d) putting the iron away
25. 25.🔮 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
26. 26.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
29. 29.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) ironing the paper (d) reading the message
30. 30.True or false: writing the message is a job for an adult. (a) False (b) True
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) lemon juice (d) a cotton bud
32. 32.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) an adult with an iron (c) a small bowl (d) a cotton bud
34. 34.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
35. 35.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) how dark the writing is (c) the kind of juice
37. 37.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
38. 38.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) letting the paper dry (d) reading the message
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a balloon (c) white paper (d) a cotton bud
40. 40.True or false: white paper is needed for the secret lemon message. (a) False (b) True

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