Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 89 · 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 needed for the secret lemon message? (a) yeast (b) a balloon (c) lemon juice (d) a battery cell
2. 2.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
3. 3.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
4. 4.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
5. 5.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
6. 6.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) how dark the writing is (c) the iron setting (d) the same paper
8. 8.True or false: reading the message is a job for an adult. (a) True (b) False
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a mirror (c) white paper (d) an adult with an iron
10. 10.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) an adult with an iron (c) a small bowl (d) a cotton bud
12. 12.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
13. 13.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a balloon (c) a small bowl (d) a cotton bud
15. 15.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) turmeric powder (d) white paper
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
18. 18.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a balloon (d) white paper
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
20. 20.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) reading the message (d) dipping the cotton bud
21. 21.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) it turned into air (c) the paper ate it (d) dry juice is see-through
22. 22.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
23. 23.⚖️ 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
24. 24.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) ironing the paper (d) reading the message
25. 25.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
26. 26.⚖️ 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 change it (c) we keep it the same
27. 27.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a cotton bud (d) a balloon
28. 28.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
29. 29.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) lemon juice
31. 31.True or false: writing the message is a job for an adult. (a) True (b) False
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
33. 33.⚖️ 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
34. 34.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
35. 35.True or false: cutting the lemon is a job for an adult. (a) True (b) False
36. 36.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
38. 38.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
39. 39.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) wash your hands (d) skip washing
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True

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