Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 967 · 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 is the odd one out? (a) reading the message (b) putting the iron away (c) letting the paper dry (d) dipping the cotton bud
2. 2.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
3. 3.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
4. 4.⚖️ 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
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
6. 6.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) putting the iron away (c) plugging in the iron (d) ironing the paper
7. 7.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) letting the paper dry (d) cutting the lemon
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
9. 9.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
10. 10.True or false: plugging in the iron is a job for an adult. (a) True (b) False
11. 11.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is magnetic (d) it is sticky
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) physical (c) musical (d) chemical
13. 13.🔮 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
14. 14.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the kind of juice (c) how dark the writing is (d) the same paper
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
17. 17.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) writing turns green (d) it gets darker
18. 18.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) reading the message
19. 19.🧺 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) a small bowl
20. 20.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) dipping the cotton bud
21. 21.🍋 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
22. 22.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
23. 23.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
24. 24.🔮 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
25. 25.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
26. 26.⚖️ 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
27. 27.⚖️ 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 keep it the same (c) we measure it
28. 28.True or false: ironing the paper is a job a child can do. (a) True (b) False
29. 29.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) reading the message (d) ironing the paper
30. 30.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
31. 31.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) reading the message (d) dipping the cotton bud
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
33. 33.⚖️ 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
34. 34.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
35. 35.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
36. 36.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
37. 37.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) yeast (c) a small bowl (d) a battery cell
39. 39.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) brown (c) green (d) blue
40. 40.True or false: reading the message is a job a child can do. (a) True (b) False

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