Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 775 · 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 mirror for the secret lemon message? (a) needed (b) not needed
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) chemical (d) magnetic
3. 3.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is cold (d) it is sticky
4. 4.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) it turned into air (d) the ink is magnetic
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) yeast (c) white paper (d) lemon juice
6. 6.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a battery cell (d) a balloon
8. 8.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
9. 9.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) letting the paper dry
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
11. 11.⚖️ 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) False (b) True
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
13. 13.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) dipping the cotton bud
14. 14.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
15. 15.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
16. 16.⚖️ 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 measure it (c) we keep it the same
17. 17.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
18. 18.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
19. 19.True or false: ironing the paper is a job a child can do. (a) True (b) False
20. 20.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
21. 21.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) writing the message (d) plugging in the iron
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) blue words (d) a rainbow
23. 23.⚖️ 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) True (b) False
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a magnet (d) a battery cell
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) white paper (d) a cotton bud
26. 26.True or false: plugging in the iron is a job for an adult. (a) False (b) True
27. 27.True or false: lemon juice is needed for the secret lemon message. (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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a battery cell (c) a small bowl (d) an adult with an iron
30. 30.⚖️ 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
31. 31.True or false: putting the iron away is a job a child can do. (a) True (b) False
32. 32.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
33. 33.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) it gets darker (d) writing turns green
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) how dark the writing is (d) the same cotton bud
35. 35.True or false: plugging in the iron is a job a child can do. (a) True (b) False
36. 36.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a balloon (c) an adult with an iron (d) a small bowl
40. 40.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it

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