Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 762 · 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.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
2. 2.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
3. 3.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) reading the message (d) plugging in the iron
4. 4.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is sticky (d) it is cold
5. 5.⚖️ 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
6. 6.⚖️ 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
7. 7.⚖️ 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 iron setting (c) the ironing time (d) the kind of juice
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) lemon juice (d) a mirror
9. 9.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) lemon juice (c) an adult with an iron (d) yeast
11. 11.⚖️ 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
12. 12.True or false: reading the message is a job for an adult. (a) True (b) False
13. 13.True or false: white paper is needed for the secret lemon message. (a) True (b) False
14. 14.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
16. 16.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) an adult with an iron
18. 18.⚖️ 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 ironing time (c) the kind of juice
19. 19.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) lemon juice (d) a battery cell
21. 21.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
22. 22.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) writing stays faint (d) it gets darker
23. 23.🍋 Secret message: who does this step — writing the message? (a) a child can do it (b) an adult does it
24. 24.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) reading the message
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
26. 26.⚖️ 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 iron setting (c) the kind of juice
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) the paper ate it (c) it turned into air (d) dry juice is see-through
28. 28.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
29. 29.⚖️ 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 keep it the same (c) we measure it
30. 30.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
31. 31.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
32. 32.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
33. 33.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) a balloon (d) a small bowl
35. 35.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
36. 36.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child
37. 37.⚖️ 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 same cotton bud
38. 38.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
40. 40.🔮 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

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