Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 741 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we measure it (c) we keep it the same
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 iron setting
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a magnet (c) lemon juice (d) an adult with an iron
4. 4.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
5. 5.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
6. 6.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) magnetic (d) physical
7. 7.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) letting the paper dry (c) ironing the paper (d) cutting the lemon
8. 8.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
9. 9.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is magnetic (d) it is sticky
10. 10.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
11. 11.⚖️ 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
12. 12.True or false: letting the paper dry is a job for an adult. (a) True (b) False
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
14. 14.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) an adult with an iron (d) a cotton bud
16. 16.⚖️ 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) how dark the writing is (c) the ironing time (d) the kind of juice
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) blue words (d) a rainbow
18. 18.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) reading the message
19. 19.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
20. 20.🛟 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
21. 21.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
22. 22.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
23. 23.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
24. 24.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
25. 25.🛟 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
26. 26.🍋 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
27. 27.True or false: cutting the lemon is a job for an adult. (a) True (b) False
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) lemon juice (c) an adult with an iron (d) yeast
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) lemon juice (d) a cotton bud
30. 30.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) ironing the paper (d) letting the paper dry
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) a small bowl (c) an adult with an iron (d) lemon juice
32. 32.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) paper turns lemony (d) the iron is brown
33. 33.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) putting the iron away (d) writing the message
34. 34.⚖️ 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 keep it the same (c) we change it
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) an adult with an iron (c) yeast (d) turmeric powder
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
37. 37.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
38. 38.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
39. 39.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) putting the iron away (d) writing the message
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a small bowl (c) turmeric powder (d) an adult with an iron

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