Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 954 · 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 “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
2. 2.True or false: plugging in the iron is a job for an adult. (a) False (b) True
3. 3.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) letting the paper dry (d) reading the message
4. 4.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
7. 7.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) reading the message (d) letting the paper dry
8. 8.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
9. 9.True or false: writing the message is a job a child can do. (a) False (b) True
10. 10.🛟 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
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a mirror (d) a small bowl
12. 12.⚖️ 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) True (b) False
13. 13.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) yeast (c) a cotton bud (d) a small bowl
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
17. 17.⚖️ 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 same cotton bud
18. 18.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) plugging in the iron
19. 19.🔍 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
20. 20.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
21. 21.True or false: letting the paper dry is a job for an adult. (a) True (b) False
22. 22.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if shaken (d) yes, if cooled
23. 23.True or false: reading the message is a job a child can do. (a) False (b) True
24. 24.True or false: writing the message is a job for an adult. (a) False (b) True
25. 25.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
26. 26.⚖️ 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
27. 27.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
28. 28.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
29. 29.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) white paper (d) a balloon
30. 30.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
31. 31.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
32. 32.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
33. 33.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) blue (d) green
34. 34.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the iron setting
36. 36.🍋 Which of these steps is a job for an adult? (a) writing the message (b) cutting the lemon (c) letting the paper dry (d) dipping the cotton bud
37. 37.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the paper ate it (d) the ink is magnetic
38. 38.🍋 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
39. 39.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a battery cell (d) white paper
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same

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