Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 715 · 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: ironing the paper is a job for an adult. (a) False (b) True
2. 2.⚖️ 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 keep it the same (c) we measure it
3. 3.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
5. 5.⚖️ 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
6. 6.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) dipping the cotton bud (d) writing the message
7. 7.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) plugging in the iron (d) letting the paper dry
8. 8.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) magnetic (d) musical
9. 9.🍋 Which of these steps is a job a child can do? (a) writing the message (b) putting the iron away (c) plugging in the iron (d) ironing the paper
10. 10.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) ironing the paper
11. 11.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
12. 12.True or false: cutting the lemon is a job for an adult. (a) False (b) True
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) white paper (d) lemon juice
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
15. 15.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
16. 16.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we measure it (c) we keep it the same
18. 18.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
19. 19.⚖️ 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
20. 20.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
21. 21.⚖️ 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
22. 22.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) cutting the lemon
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a battery cell (d) a cotton bud
24. 24.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
25. 25.True or false: reading the message is a job a child can do. (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 change it (c) we keep it the same
27. 27.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a balloon (c) a magnet (d) yeast
28. 28.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) it turned into air (d) dry juice is see-through
29. 29.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
30. 30.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) letting the paper dry (c) reading the message (d) writing the message
31. 31.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) letting the paper dry (c) cutting the lemon (d) plugging in the iron
32. 32.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) reading the message (d) plugging in the iron
33. 33.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
34. 34.🧺 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
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) white paper (c) an adult with an iron (d) lemon juice
36. 36.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) letting the paper dry
37. 37.⚖️ 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
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the iron setting (c) the same paper (d) the kind of juice
39. 39.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
40. 40.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it

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