Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 688 · 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) a cotton bud (b) turmeric powder (c) an adult with an iron (d) lemon juice
2. 2.⚖️ 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) how dark the writing is (c) the ironing time (d) the kind of juice
3. 3.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) putting the iron away (d) letting the paper dry
4. 4.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
5. 5.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
6. 6.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
7. 7.True or false: writing the message is a job a child can do. (a) False (b) True
8. 8.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a magnet (c) yeast (d) a mirror
9. 9.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
10. 10.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
11. 11.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
12. 12.⚖️ 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
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
14. 14.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) lemon juice (c) white paper (d) a battery cell
15. 15.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
16. 16.🔮 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
17. 17.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) reading the message (d) cutting the lemon
18. 18.⚖️ 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
19. 19.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
20. 20.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) white paper (c) lemon juice (d) a cotton bud
22. 22.⚖️ 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) False (b) True
23. 23.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
25. 25.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
26. 26.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
27. 27.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) lick your fingers (d) wash your hands
28. 28.⚖️ 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 same paper (c) the kind of juice (d) the same cotton bud
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (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 paper”? (a) we change it (b) we keep it the same (c) we measure it
31. 31.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a balloon (d) a small bowl
32. 32.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
34. 34.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
35. 35.⚖️ 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
36. 36.🍋 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
37. 37.True or false: cutting the lemon is a job a child can do. (a) True (b) False
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) yeast (c) a small bowl (d) white paper
39. 39.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
40. 40.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) the paper floats (c) writing turns green (d) it gets darker

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