Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 729 · 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.True or false: letting the paper dry is a job for an adult. (a) True (b) False
2. 2.True or false: cutting the lemon is a job for an adult. (a) False (b) True
3. 3.🍋 Which of these steps is a job a child can do? (a) reading the message (b) cutting the lemon (c) putting the iron away (d) ironing the paper
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
5. 5.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) reading the message (d) ironing the paper
6. 6.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
7. 7.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
8. 8.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) writing the message (d) plugging in the iron
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
10. 10.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
11. 11.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) lemon juice (d) a magnet
13. 13.⚖️ 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
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the same paper
15. 15.⚖️ 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) False (b) True
16. 16.True or false: reading the message is a job for an adult. (a) True (b) False
17. 17.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing stays faint (d) writing turns green
18. 18.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) whoever is fastest (d) any child
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we measure it (c) we keep it the same
20. 20.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
22. 22.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
23. 23.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a battery cell (d) a cotton bud
25. 25.⚖️ 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
26. 26.⚖️ 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
27. 27.⚖️ 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) True (b) False
28. 28.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
29. 29.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
30. 30.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
31. 31.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
32. 32.True or false: writing the message is a job a child can do. (a) False (b) True
33. 33.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) writing the message (c) plugging in the iron (d) ironing the paper
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a small bowl (d) a magnet
35. 35.⚖️ 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
36. 36.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) cutting the lemon (c) writing the message (d) dipping the cotton bud
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
38. 38.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the ink is magnetic (d) the paper ate it
39. 39.⚖️ 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
40. 40.⚖️ 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 iron setting (c) the kind of juice

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