Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 136 · 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? True or false: the iron setting is what we measure. (a) False (b) True
2. 2.⚖️ 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
3. 3.⚖️ 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
4. 4.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
5. 5.⚖️ 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 change it (c) we measure it
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) white paper (d) yeast
7. 7.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) plugging in the iron (d) cutting the lemon
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same cotton bud (c) how dark the writing is (d) the ironing time
9. 9.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) ironing the paper (d) cutting the lemon
10. 10.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a battery cell (d) a small bowl
11. 11.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
12. 12.⚖️ 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
13. 13.⚖️ 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 change it (c) we keep it the same
14. 14.⚖️ 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 same cotton bud (c) how dark the writing is
15. 15.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) yeast (c) lemon juice (d) an adult with an iron
16. 16.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
17. 17.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
18. 18.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
19. 19.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
20. 20.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
21. 21.True or false: reading the message is a job for an adult. (a) True (b) False
22. 22.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is cold (d) it is magnetic
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a mirror (c) lemon juice (d) a cotton bud
24. 24.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
25. 25.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) a battery cell (d) a cotton bud
27. 27.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
28. 28.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
29. 29.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a battery cell (c) a mirror (d) a cotton bud
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) an adult with an iron (d) a mirror
31. 31.🛟 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
32. 32.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the iron is brown (c) the juice scorches first (d) heat adds colour
33. 33.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
34. 34.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
35. 35.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) a rainbow (d) almost nothing
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
38. 38.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) letting the paper dry (c) plugging in the iron (d) writing the message
39. 39.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
40. 40.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed

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