Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 825 · 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 does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) heat adds colour (d) the juice scorches first
2. 2.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
3. 3.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
4. 4.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
5. 5.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is sticky (d) it is magnetic
6. 6.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
8. 8.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) yeast (d) a small bowl
9. 9.⚖️ 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
10. 10.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) dipping the cotton bud
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) lemon juice (d) a balloon
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) the same cotton bud (d) how dark the writing is
13. 13.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) dipping the cotton bud (d) reading the message
14. 14.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
15. 15.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, if shaken (d) yes, in the dark
16. 16.🍋 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
17. 17.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
19. 19.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) skip washing (d) rub your eyes
20. 20.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
21. 21.⚖️ 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) True (b) False
22. 22.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) a rainbow (d) almost nothing
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) a cotton bud (d) a battery cell
24. 24.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) lemon juice (d) a cotton bud
26. 26.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
28. 28.True or false: putting the iron away is a job for an adult. (a) True (b) False
29. 29.True or false: writing the message is a job a child can do. (a) False (b) True
30. 30.🧺 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) an adult with an iron
31. 31.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) a battery cell
34. 34.⚖️ 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 paper
35. 35.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
37. 37.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
38. 38.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
39. 39.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
40. 40.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) plugging in the iron

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