Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 519 · 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.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a magnet (d) a cotton bud
2. 2.⚖️ 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
3. 3.True or false: writing the message is a job for an adult. (a) False (b) True
4. 4.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
5. 5.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a battery cell (d) lemon juice
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing stays faint (d) writing turns green
7. 7.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
8. 8.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
9. 9.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we keep it the same (c) we change it
11. 11.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
12. 12.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is cold (d) it is sticky
13. 13.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) cutting the lemon (d) ironing the paper
14. 14.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
15. 15.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
16. 16.⚖️ 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 same cotton bud (c) the kind of juice (d) the same paper
17. 17.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) ironing the paper (d) dipping the cotton bud
18. 18.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, if cooled (d) yes, in the dark
19. 19.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
21. 21.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we change it (c) we measure it
23. 23.⚖️ 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 keep it the same (c) we change it
24. 24.⚖️ 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 iron setting (d) the ironing time
25. 25.⚖️ 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
26. 26.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a battery cell (d) white paper
27. 27.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) the youngest child (d) whoever is fastest
28. 28.True or false: reading the message is a job for an adult. (a) True (b) False
29. 29.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a small bowl (c) yeast (d) a cotton bud
31. 31.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
32. 32.⚖️ 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
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) a battery cell (d) an adult with an iron
34. 34.🧺 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) a cotton bud (d) a battery cell
35. 35.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
36. 36.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
37. 37.⚖️ 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
38. 38.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
39. 39.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False

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