Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 98 · 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.⚖️ 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) False (b) True
2. 2.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) an adult with an iron (d) a magnet
3. 3.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) putting the iron away (d) cutting the lemon
4. 4.⚖️ 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 same paper (d) the kind of juice
5. 5.⚖️ 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
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) False (b) True
7. 7.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) letting the paper dry (d) plugging in the iron
8. 8.⚖️ 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
9. 9.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) the ink is magnetic (d) dry juice is see-through
10. 10.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the juice scorches first (d) the iron is brown
11. 11.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
12. 12.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
13. 13.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
14. 14.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
15. 15.True or false: ironing the paper is a job a child can do. (a) False (b) True
16. 16.⚖️ 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) how dark the writing is (c) the same paper (d) the kind of juice
17. 17.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
18. 18.True or false: putting the iron away is a job a child can do. (a) False (b) True
19. 19.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
20. 20.🔮 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
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the ironing time (c) how dark the writing is
22. 22.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
23. 23.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) a battery cell (d) lemon juice
25. 25.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
26. 26.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) plugging in the iron (d) cutting the lemon
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) lemon juice (d) a battery cell
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) a mirror (d) a small bowl
31. 31.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) plugging in the iron
32. 32.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
33. 33.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
34. 34.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
35. 35.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
36. 36.True or false: writing the message is a job for an adult. (a) False (b) True
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) a battery cell (d) a cotton bud
38. 38.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) rub your eyes (d) skip washing
39. 39.🍋 Which of these steps is a job for an adult? (a) writing the message (b) cutting the lemon (c) dipping the cotton bud (d) reading the message
40. 40.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a small bowl (d) a magnet

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