Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 511 · 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) white paper (b) lemon juice (c) a mirror (d) a small bowl
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) the ironing time (c) how dark the writing is
3. 3.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) the paper floats (d) it gets darker
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) white paper (d) a balloon
5. 5.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) turmeric powder (d) white paper
8. 8.True or false: reading the message is a job a child can do. (a) True (b) False
9. 9.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
10. 10.⚖️ 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) True (b) False
11. 11.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) white (d) green
12. 12.⚖️ 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 paper
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) True (b) False
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
15. 15.⚖️ 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
16. 16.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
17. 17.True or false: white paper is needed for the secret lemon message. (a) False (b) True
18. 18.⚖️ 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 measure it (c) we keep it the same
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the same paper (d) the same cotton bud
20. 20.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
21. 21.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) a cotton bud (d) yeast
23. 23.True or false: writing the message is a job for an adult. (a) True (b) False
24. 24.🍋 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) plugging in the iron
25. 25.🔍 Which is the odd one out? (a) writing the message (b) reading the message (c) plugging in the iron (d) dipping the cotton bud
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same cotton bud (c) the iron setting (d) the ironing time
27. 27.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
28. 28.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
29. 29.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
30. 30.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) musical (c) magnetic (d) chemical
31. 31.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
32. 32.🍋 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
33. 33.True or false: letting the paper dry is a job for an adult. (a) False (b) True
34. 34.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) putting the iron away (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 paper”? (a) we measure it (b) we change it (c) we keep it the same
36. 36.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) letting the paper dry (d) reading the message
37. 37.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) turmeric powder (c) a magnet (d) white paper
38. 38.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
39. 39.True or false: yeast is needed for the secret lemon message. (a) False (b) True
40. 40.🍋 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

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