Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 145 · 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: turmeric powder is needed for the secret lemon message. (a) False (b) True
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
4. 4.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) blue words (d) almost nothing
5. 5.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) turmeric powder
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) a battery cell (d) a balloon
8. 8.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) reading the message (c) letting the paper dry (d) writing the message
9. 9.🍋 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
10. 10.⚖️ 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 kind of juice (c) the same cotton bud (d) the same paper
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a battery cell (c) an adult with an iron (d) lemon juice
12. 12.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) the youngest child (d) any child
13. 13.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
14. 14.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) writing the message (d) reading the message
15. 15.⚖️ 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
16. 16.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a battery cell (d) lemon juice
18. 18.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
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) True (b) False
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a small bowl (c) a cotton bud (d) white paper
21. 21.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a mirror (d) an adult with an iron
22. 22.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) reading the message (d) ironing the paper
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we change it (c) we measure it
24. 24.⚖️ 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) True (b) False
25. 25.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
26. 26.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
27. 27.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) letting the paper dry (d) cutting the lemon
28. 28.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) letting the paper dry (d) dipping the cotton bud
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) a cotton bud (d) lemon juice
30. 30.🔍 Which is the odd one out? (a) writing the message (b) putting the iron away (c) cutting the lemon (d) plugging in the iron
31. 31.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) letting the paper dry (d) plugging in the iron
32. 32.⚖️ 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) True (b) False
33. 33.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same cotton bud (d) the same paper
35. 35.True or false: plugging in the iron is a job a child can do. (a) False (b) True
36. 36.🍋 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
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
38. 38.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) writing the message (c) dipping the cotton bud (d) reading the message
39. 39.True or false: cutting the lemon is a job a child can do. (a) False (b) True
40. 40.True or false: putting the iron away is a job for an adult. (a) True (b) False

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