Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 810 · 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.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a magnet (c) a balloon (d) a mirror
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same paper (c) the kind of juice (d) how dark the writing is
3. 3.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
4. 4.⚖️ 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) False (b) True
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
6. 6.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
7. 7.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
8. 8.🍋 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
9. 9.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) reading the message (d) cutting the lemon
10. 10.True or false: cutting the lemon is a job a child can do. (a) False (b) True
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) a cotton bud (d) a battery cell
12. 12.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) lick your fingers (d) skip washing
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the kind of juice (c) the same cotton bud (d) the iron setting
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) turmeric powder (d) a balloon
15. 15.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
16. 16.🔍 Which is the odd one out? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) plugging in the iron
17. 17.⚖️ 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
18. 18.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
19. 19.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
21. 21.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) reading the message (d) ironing the paper
22. 22.True or false: writing the message is a job a child can do. (a) False (b) True
23. 23.⚖️ 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
24. 24.⚖️ 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 same cotton bud (c) the kind of juice
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a balloon (d) an adult with an iron
26. 26.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
27. 27.True or false: ironing the paper is a job for an adult. (a) True (b) False
28. 28.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) a magnet (d) a battery cell
29. 29.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
30. 30.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
31. 31.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing stays faint (c) writing turns green (d) the paper floats
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a magnet (d) a cotton bud
34. 34.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
35. 35.⚖️ 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) True (b) False
36. 36.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) reading the message (c) ironing the paper (d) putting the iron away
37. 37.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) heat adds colour (d) the iron is brown
38. 38.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
39. 39.⚖️ 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 measure it (c) we keep it the same
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False

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