Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 479 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
2. 2.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
3. 3.True or false: yeast is needed for the secret lemon message. (a) False (b) True
4. 4.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) paper turns lemony (d) the iron is brown
5. 5.⚖️ 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
6. 6.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
7. 7.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a magnet (d) lemon juice
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
10. 10.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
11. 11.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
12. 12.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a battery cell (d) white paper
14. 14.True or false: plugging in the iron is a job for an adult. (a) False (b) True
15. 15.True or false: white paper is needed for the secret lemon message. (a) True (b) False
16. 16.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
17. 17.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
18. 18.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
19. 19.🛟 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
20. 20.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) skip washing (d) lick your fingers
21. 21.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) a mirror (d) a cotton bud
22. 22.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
23. 23.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) writing turns green (d) it gets darker
24. 24.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) letting the paper dry (d) cutting the lemon
25. 25.⚖️ 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 change it (c) we measure it
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
27. 27.🍋 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
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) whoever is fastest (d) the youngest child
29. 29.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
30. 30.True or false: cutting the lemon is a job a child can do. (a) False (b) True
31. 31.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) a small bowl (d) lemon juice
33. 33.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) dipping the cotton bud (d) cutting the lemon
34. 34.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
35. 35.⚖️ 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
36. 36.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) a small bowl (d) yeast
37. 37.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
38. 38.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) cutting the lemon (d) putting the iron away
39. 39.⚖️ 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 ironing time
40. 40.True or false: plugging in the iron is a job a child can do. (a) False (b) True

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