Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 732 · 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 steps is a job a child can do? (a) dipping the cotton bud (b) cutting the lemon (c) plugging in the iron (d) putting the iron away
2. 2.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
4. 4.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
5. 5.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
6. 6.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) cutting the lemon
7. 7.⚖️ 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
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 change it (c) we keep it the same
9. 9.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the kind of juice (d) the same paper
11. 11.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) musical (d) magnetic
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) yeast (c) white paper (d) an adult with an iron
14. 14.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) any child (c) whoever is fastest (d) the youngest child
15. 15.🧺 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 balloon
16. 16.🔮 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
17. 17.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) a mirror (d) lemon juice
18. 18.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
19. 19.⚖️ 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
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a battery cell (d) an adult with an 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 change it (b) we keep it the same (c) we measure it
22. 22.True or false: ironing the paper is a job for an adult. (a) False (b) True
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
24. 24.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a small bowl (c) lemon juice (d) an adult with an iron
26. 26.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
27. 27.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
28. 28.True or false: ironing the paper is a job a child can do. (a) False (b) True
29. 29.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) plugging in the iron (d) letting the paper dry
30. 30.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
31. 31.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) dipping the cotton bud (d) letting the paper dry
32. 32.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
33. 33.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) writing the message (d) putting the iron away
34. 34.True or false: reading the message is a job for an adult. (a) True (b) False
35. 35.⚖️ 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
36. 36.⚖️ 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 cotton bud
37. 37.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) cutting the lemon
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a cotton bud (d) yeast
39. 39.⚖️ 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
40. 40.True or false: writing the message is a job for an adult. (a) True (b) False

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