Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 711 · 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: a balloon is not needed for the secret lemon message. (a) True (b) False
2. 2.⚖️ 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 kind of juice (c) the ironing time
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
4. 4.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
5. 5.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
6. 6.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
7. 7.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) lemon juice (c) white paper (d) an adult with an iron
9. 9.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
10. 10.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
11. 11.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) a mirror (d) lemon juice
14. 14.True or false: ironing the paper is a job for an adult. (a) False (b) True
15. 15.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
16. 16.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
17. 17.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
18. 18.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) cutting the lemon
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
20. 20.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
21. 21.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
22. 22.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
23. 23.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) reading the message
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
25. 25.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
26. 26.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) lick your fingers (d) wash your hands
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) lemon juice (d) a balloon
28. 28.⚖️ 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
29. 29.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
30. 30.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) reading the message (c) writing the message (d) dipping the cotton bud
31. 31.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) dark brown words (d) blue words
32. 32.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) it turned into air (d) the paper ate it
33. 33.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) cutting the lemon (d) dipping the cotton bud
34. 34.🍋 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
35. 35.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) letting the paper dry (d) ironing the paper
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the iron setting (c) the same paper (d) the kind of juice
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) a balloon (d) turmeric powder
38. 38.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
39. 39.⚖️ 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
40. 40.True or false: putting the iron away is a job for an adult. (a) True (b) False

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