Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 139 · 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 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
2. 2.⚖️ 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
3. 3.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
4. 4.True or false: putting the iron away is a job a child can do. (a) True (b) False
5. 5.True or false: letting the paper dry is a job for an adult. (a) False (b) True
6. 6.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) writing the message
7. 7.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
8. 8.⚖️ 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 change it (c) we keep it the same
9. 9.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) yeast (d) a battery cell
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.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
13. 13.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) letting the paper dry (d) plugging in the iron
14. 14.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
15. 15.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
16. 16.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) it gets darker (d) writing stays faint
17. 17.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) white (d) blue
18. 18.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
19. 19.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud
20. 20.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) reading the message (d) cutting the lemon
21. 21.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) white paper (c) a small bowl (d) turmeric powder
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
24. 24.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
25. 25.🛟 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
26. 26.True or false: turmeric powder 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? Which of these is what we measure? (a) the iron setting (b) how dark the writing is (c) the same paper (d) the ironing time
28. 28.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
29. 29.True or false: a balloon 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) plugging in the iron (b) reading the message (c) cutting the lemon (d) ironing the paper
31. 31.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
32. 32.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) an adult with an iron (d) yeast
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a magnet (d) a battery cell
35. 35.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
36. 36.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a battery cell (d) a small bowl
37. 37.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
38. 38.🔮 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
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) a cotton bud (d) an adult with an iron
40. 40.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) magnetic (c) physical (d) musical

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