Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 302 · 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? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) yeast (c) a cotton bud (d) an adult with an iron
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) an adult with an iron (d) white paper
5. 5.⚖️ 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 keep it the same (c) we measure it
6. 6.True or false: plugging in the iron is a job for an adult. (a) False (b) True
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) yeast (c) an adult with an iron (d) a cotton bud
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a balloon (d) a small bowl
9. 9.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) reading the message (d) plugging in the iron
10. 10.True or false: putting the iron away is a job a child can do. (a) True (b) False
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a mirror (d) a small bowl
12. 12.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
14. 14.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
15. 15.🍋 Secret message: who does this step — cutting the lemon? (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? True or false: how dark the writing is is what we measure. (a) True (b) False
17. 17.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
18. 18.True or false: letting the paper dry is a job for an adult. (a) False (b) True
19. 19.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
20. 20.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) skip washing (d) wash your hands
21. 21.⚖️ 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) the same paper (c) how dark the writing is (d) the kind of juice
22. 22.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
23. 23.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
24. 24.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) dipping the cotton bud
25. 25.🧺 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) a magnet
26. 26.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) letting the paper dry (d) putting the iron away
27. 27.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
28. 28.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
29. 29.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
30. 30.⚖️ 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 ironing time (c) the kind of juice (d) the same paper
31. 31.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) writing the message
32. 32.True or false: cutting the lemon is a job for an adult. (a) True (b) False
33. 33.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) ironing the paper
34. 34.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) plugging in the iron (c) ironing the paper (d) putting the iron away
35. 35.⚖️ 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
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? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
38. 38.True or false: writing the message is a job for an adult. (a) False (b) True
39. 39.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) reading the message
40. 40.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True

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