Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 388 · 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.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
2. 2.True or false: yeast is needed for the secret lemon message. (a) True (b) False
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
4. 4.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
5. 5.🍋 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
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) a mirror (d) lemon juice
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
8. 8.⚖️ 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) how dark the writing is (c) the iron setting
9. 9.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) cutting the lemon (c) putting the iron away (d) ironing the paper
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a cotton bud (d) yeast
11. 11.⚖️ 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 cotton bud (c) how dark the writing is
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
13. 13.⚖️ 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
14. 14.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
15. 15.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) white paper (c) a small bowl (d) an adult with an iron
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
18. 18.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
19. 19.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a magnet (d) a battery cell
20. 20.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) plugging in the iron
21. 21.⚖️ 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
22. 22.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
23. 23.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the same paper (c) the kind of juice
25. 25.True or false: reading the message is a job a child can do. (a) True (b) False
26. 26.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) dark brown words (d) a rainbow
27. 27.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
28. 28.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
29. 29.True or false: putting the iron away is a job a child can do. (a) False (b) True
30. 30.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) a magnet (d) white paper
32. 32.🔍 Which is the odd one out? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (d) writing the message
33. 33.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) writing the message (d) plugging in the iron
34. 34.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) yeast (d) white paper
36. 36.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) cutting the lemon (d) reading the message
37. 37.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) putting the iron away (d) ironing the paper
38. 38.⚖️ 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
39. 39.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) ironing the paper (c) writing the message (d) dipping the cotton bud
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a cotton bud (d) a battery cell

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