Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 79 · 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? Which of these is the one thing we change? (a) how dark the writing is (b) the kind of juice (c) the same cotton bud (d) the same paper
2. 2.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
3. 3.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) dry juice is see-through (d) the ink is magnetic
4. 4.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) cutting the lemon
5. 5.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) plugging in the iron (d) ironing the paper
6. 6.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
8. 8.🔍 Which is the odd one out? (a) putting the iron away (b) letting the paper dry (c) cutting the lemon (d) ironing the paper
9. 9.⚖️ 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
10. 10.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a mirror (c) turmeric powder (d) a magnet
11. 11.⚖️ 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
12. 12.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) plugging in the iron (d) letting the paper dry
13. 13.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) almost nothing (c) a rainbow (d) blue words
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same cotton bud (b) how dark the writing is (c) the ironing time (d) the kind of juice
15. 15.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
16. 16.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
17. 17.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
18. 18.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
19. 19.🔍 Which is the odd one out? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) writing the message
20. 20.⚖️ 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) False (b) True
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) the paper floats (d) writing turns green
22. 22.True or false: ironing the paper is a job a child can do. (a) False (b) True
23. 23.True or false: plugging in the iron is a job a child can do. (a) False (b) True
24. 24.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) skip washing (d) rub your eyes
25. 25.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) reading the message
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) the iron is brown (d) heat adds colour
28. 28.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a cotton bud (d) a magnet
29. 29.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
30. 30.True or false: white paper is needed for the secret lemon message. (a) False (b) True
31. 31.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
32. 32.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
33. 33.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
34. 34.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is magnetic (d) it is cold
35. 35.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) only an adult (d) whoever is fastest
36. 36.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) reading the message (d) writing the message
37. 37.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) writing the message (d) putting the iron away
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) True (b) False
39. 39.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
40. 40.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) ironing the paper (d) dipping the cotton bud

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