Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 150 · 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 a balloon for the secret lemon message? (a) needed (b) not needed
2. 2.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) writing the message (d) letting the paper dry
3. 3.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
6. 6.⚖️ 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 kind of juice (c) the same paper
7. 7.⚖️ 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
8. 8.🍋 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
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a balloon (d) lemon juice
10. 10.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) ironing the paper (c) putting the iron away (d) cutting the lemon
11. 11.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
12. 12.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
15. 15.True or false: cutting the lemon is a job for an adult. (a) False (b) True
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) a small bowl (d) a magnet
17. 17.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a mirror (d) white paper
19. 19.True or false: reading the message is a job for an adult. (a) True (b) False
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
21. 21.🧺 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 battery cell (d) white paper
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical
23. 23.True or false: cutting the lemon is a job a child can do. (a) False (b) True
24. 24.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
25. 25.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) ironing the paper (d) plugging in the iron
26. 26.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
27. 27.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
28. 28.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
29. 29.True or false: putting the iron away is a job for an adult. (a) True (b) False
30. 30.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) cutting the lemon (d) plugging in the iron
31. 31.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) writing the message
32. 32.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) letting the paper dry
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) yeast (d) lemon juice
34. 34.True or false: white paper is needed for the secret lemon message. (a) True (b) False
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
36. 36.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
37. 37.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) writing the message
38. 38.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
39. 39.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
40. 40.True or false: a mirror is needed for the secret lemon message. (a) False (b) True

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