Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 214 · 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 what we measure? (a) the ironing time (b) the kind of juice (c) the iron setting (d) how dark the writing is
2. 2.⚖️ 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 ironing time
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the ironing time (c) the iron setting (d) the kind of juice
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) lemon juice (c) white paper (d) a small bowl
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
6. 6.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we measure it (c) we change it
8. 8.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
9. 9.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
10. 10.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a small bowl (c) yeast (d) a mirror
11. 11.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) letting the paper dry (d) putting the iron away
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a mirror (d) white paper
13. 13.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
14. 14.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) dipping the cotton bud (c) putting the iron away (d) ironing the paper
15. 15.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
16. 16.⚖️ 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 keep it the same (c) we measure it
17. 17.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
18. 18.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
19. 19.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
20. 20.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) white paper (c) turmeric powder (d) yeast
21. 21.⚖️ 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
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
23. 23.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
24. 24.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a battery cell (c) an adult with an iron (d) turmeric powder
25. 25.True or false: putting the iron away is a job a child can do. (a) False (b) True
26. 26.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) green (c) blue (d) white
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
28. 28.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
29. 29.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
30. 30.⚖️ 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
31. 31.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
32. 32.True or false: putting the iron away is a job for an adult. (a) True (b) False
33. 33.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
34. 34.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
35. 35.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a battery cell (c) lemon juice (d) a cotton bud
37. 37.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) cutting the lemon (d) dipping the cotton bud
38. 38.True or false: lemon juice is not 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 keep it the same (c) we change it
40. 40.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a cotton bud (d) a magnet

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