Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 280 · 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.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
3. 3.🔮 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
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a small bowl (c) lemon juice (d) white paper
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) white paper (d) a balloon
7. 7.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) writing the message (d) cutting the lemon
8. 8.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the ironing time (c) the same paper (d) the iron setting
10. 10.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) any child (d) whoever is fastest
11. 11.True or false: plugging in the iron is a job a child can do. (a) False (b) True
12. 12.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
13. 13.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) letting the paper dry
14. 14.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) reading the message (c) ironing the paper (d) cutting the lemon
15. 15.🛟 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
16. 16.⚖️ 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) False (b) True
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we change it (c) we keep it the same
18. 18.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) yeast (d) a mirror
19. 19.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
20. 20.⚖️ 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
21. 21.🍋 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
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a small bowl (d) a magnet
23. 23.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) letting the paper dry (d) writing the message
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) yeast (b) a cotton bud (c) lemon juice (d) an adult with an iron
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) turmeric powder (c) an adult with an iron (d) lemon juice
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) white paper (d) yeast
29. 29.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
30. 30.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) letting the paper dry (c) putting the iron away (d) plugging in the iron
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a battery cell (d) white paper
32. 32.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
33. 33.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
34. 34.True or false: writing the message is a job for an adult. (a) True (b) False
35. 35.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
36. 36.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
37. 37.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
38. 38.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
39. 39.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) white (d) green
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the iron setting (d) the kind of juice

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