Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 969 · 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 must children keep their fingers away from the iron? (a) it can burn skin (b) it is magnetic (c) it is sticky (d) it is cold
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
3. 3.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the iron is brown (d) the juice scorches first
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a battery cell (c) white paper (d) a small bowl
6. 6.🛟 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
7. 7.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
9. 9.⚖️ 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
10. 10.⚖️ 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 iron setting (c) how dark the writing is (d) the kind of juice
11. 11.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
12. 12.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) brown (d) white
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) an adult with an iron (c) a small bowl (d) a cotton bud
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
16. 16.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) dry juice is see-through (d) the ink is magnetic
17. 17.⚖️ 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
18. 18.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a mirror (d) turmeric powder
19. 19.⚖️ 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 same paper (c) the kind of juice (d) the ironing time
20. 20.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a battery cell (d) a cotton bud
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) a small bowl (d) white paper
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a small bowl (d) yeast
24. 24.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
26. 26.True or false: white paper is needed for the secret lemon message. (a) True (b) False
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we keep it the same (c) we change it
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
29. 29.True or false: reading the message is a job for an adult. (a) True (b) False
30. 30.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) cutting the lemon (d) dipping the cotton bud
31. 31.🔮 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
32. 32.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
33. 33.True or false: putting the iron away is a job for an adult. (a) True (b) False
34. 34.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) reading the message (d) plugging in the iron
35. 35.🔮 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
36. 36.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
37. 37.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
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.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) turmeric powder (c) white paper (d) a cotton bud

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