Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 231 · 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 is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) a cotton bud (d) a balloon
2. 2.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
3. 3.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) a cotton bud (d) a battery cell
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
6. 6.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) writing the message (d) ironing the paper
7. 7.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
8. 8.True or false: writing the message is a job for an adult. (a) False (b) True
9. 9.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a cotton bud (d) a battery cell
11. 11.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) a cotton bud (d) white paper
13. 13.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) reading the message
14. 14.True or false: white paper is needed for the secret lemon message. (a) False (b) True
15. 15.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
16. 16.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green
17. 17.⚖️ 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
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) white paper (d) a magnet
19. 19.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) turmeric powder (c) white paper (d) lemon juice
20. 20.⚖️ 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) True (b) False
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a battery cell (c) a balloon (d) yeast
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the ironing time (c) the same paper (d) the kind of juice
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a mirror (d) lemon juice
25. 25.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) reading the message (d) putting the iron away
26. 26.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
27. 27.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it can burn skin (d) it is cold
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
29. 29.True or false: plugging in the iron is a job a child can do. (a) False (b) True
30. 30.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it
32. 32.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
33. 33.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
35. 35.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
37. 37.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) letting the paper dry (d) ironing the paper
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) lemon juice (c) turmeric powder (d) a battery cell
39. 39.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) ironing the paper (c) plugging in the iron (d) putting the iron away
40. 40.True or false: yeast is needed for the secret lemon message. (a) True (b) False

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