Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 78 · 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.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) dry juice is see-through (d) it turned into air
2. 2.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
3. 3.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) plugging in the iron
4. 4.True or false: putting the iron away is a job for an adult. (a) True (b) False
5. 5.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
6. 6.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
7. 7.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
8. 8.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) letting the paper dry (c) reading the message (d) writing the message
9. 9.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
10. 10.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) lemon juice (d) a mirror
11. 11.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
12. 12.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
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) False (b) True
14. 14.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) cutting the lemon (d) reading the message
15. 15.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
16. 16.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
17. 17.⚖️ 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 ironing time (c) the same cotton bud (d) the kind of juice
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same paper (c) how dark the writing is (d) the same cotton bud
19. 19.⚖️ 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
20. 20.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) letting the paper dry
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
22. 22.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
23. 23.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) dipping the cotton bud (c) ironing the paper (d) putting the iron away
24. 24.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) lemon juice (d) white paper
26. 26.⚖️ 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
27. 27.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) lemon juice (d) white paper
29. 29.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green
30. 30.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
31. 31.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
32. 32.True or false: yeast is needed for the secret lemon message. (a) True (b) False
33. 33.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
34. 34.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) writing the message (d) reading the message
35. 35.True or false: reading the message is a job for an adult. (a) False (b) True
36. 36.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) reading the message
37. 37.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
38. 38.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
39. 39.🍋 Which of these steps is a job for an adult? (a) writing the message (b) putting the iron away (c) letting the paper dry (d) dipping the cotton bud
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False

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