Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 34 · 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.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we change it (c) we keep it the same
3. 3.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) letting the paper dry (d) reading the message
4. 4.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
5. 5.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) lick your fingers (c) rub your eyes (d) skip washing
6. 6.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) almost nothing (d) blue words
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a mirror (d) a small bowl
8. 8.True or false: yeast is needed for the secret lemon message. (a) False (b) True
9. 9.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
10. 10.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
11. 11.⚖️ 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) True (b) False
12. 12.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
13. 13.True or false: ironing the paper is a job for an adult. (a) True (b) False
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is sticky (c) it is magnetic (d) it is cold
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
16. 16.True or false: letting the paper dry is a job a child can do. (a) False (b) True
17. 17.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) putting the iron away (c) cutting the lemon (d) ironing the paper
18. 18.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same paper
20. 20.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
21. 21.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
22. 22.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) turmeric powder (d) lemon juice
23. 23.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
24. 24.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
25. 25.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
27. 27.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) plugging in the iron (d) cutting the lemon
28. 28.True or false: plugging in the iron is a job a child can do. (a) False (b) True
29. 29.True or false: reading the message is a job a child can do. (a) False (b) True
30. 30.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) reading the message (d) cutting the lemon
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a magnet (c) a cotton bud (d) a small bowl
32. 32.⚖️ 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 same paper (c) the same cotton bud (d) how dark the writing is
33. 33.True or false: putting the iron away is a job for an adult. (a) False (b) True
34. 34.True or false: putting the iron away is a job a child can do. (a) False (b) True
35. 35.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
36. 36.🛟 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
37. 37.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) ironing the paper (d) dipping the cotton bud
38. 38.True or false: cutting the lemon is a job a child can do. (a) True (b) False
39. 39.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) cutting the lemon (d) letting the paper dry
40. 40.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown

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