Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 216 · 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 the one thing we change? (a) the iron setting (b) the kind of juice (c) the same cotton bud (d) the same paper
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
3. 3.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
4. 4.⚖️ 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
5. 5.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
6. 6.⚖️ 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
7. 7.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
9. 9.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
10. 10.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) the youngest child (d) only an adult
11. 11.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
12. 12.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a balloon (c) turmeric powder (d) an adult with an iron
13. 13.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) blue (d) green
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) yeast (c) lemon juice (d) a balloon
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) yeast (d) lemon juice
16. 16.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
17. 17.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) it gets darker (c) writing stays faint (d) the paper floats
18. 18.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) putting the iron away (d) letting the paper dry
19. 19.⚖️ 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
20. 20.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
21. 21.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
22. 22.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
23. 23.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
24. 24.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
25. 25.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
26. 26.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) the iron is brown (d) paper turns lemony
27. 27.True or false: cutting the lemon is a job a child can do. (a) False (b) True
28. 28.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) dipping the cotton bud (d) plugging in the iron
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same paper (b) how dark the writing is (c) the kind of juice
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) how dark the writing is (c) the ironing time (d) the same paper
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) a small bowl (d) yeast
32. 32.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
33. 33.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
35. 35.⚖️ 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 keep it the same (c) we change it
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) a magnet (d) an adult with an iron
37. 37.True or false: reading the message is a job for an adult. (a) False (b) True
38. 38.True or false: cutting the lemon is a job for an adult. (a) False (b) True
39. 39.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True

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