Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 513 · 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) an adult with an iron (c) turmeric powder (d) a small bowl
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
3. 3.⚖️ 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
4. 4.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
6. 6.True or false: ironing the paper is a job for an adult. (a) True (b) False
7. 7.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it is magnetic (d) it can burn skin
8. 8.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
9. 9.⚖️ 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 paper (c) how dark the writing is
10. 10.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) a balloon (d) lemon juice
12. 12.True or false: writing the message is a job for an adult. (a) False (b) True
13. 13.🔍 Which is the odd one out? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) writing the message
14. 14.⚖️ 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
15. 15.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the same paper (c) the ironing time (d) how dark the writing is
17. 17.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: a mirror is not needed for the secret lemon message. (a) False (b) True
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
20. 20.🔍 Which is the odd one out? (a) dipping the cotton bud (b) cutting the lemon (c) writing the message (d) letting the paper dry
21. 21.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
22. 22.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing stays faint (d) writing turns green
23. 23.🛟 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
24. 24.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) an adult with an iron
25. 25.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) magnetic (d) musical
26. 26.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
27. 27.⚖️ 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
28. 28.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) skip washing (d) rub your eyes
29. 29.True or false: plugging in the iron is a job a child can do. (a) False (b) True
30. 30.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if shaken (c) yes, if cooled (d) no, it stays brown
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
32. 32.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
33. 33.⚖️ 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
34. 34.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) a rainbow (d) blue words
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a small bowl (c) an adult with an iron (d) lemon juice
36. 36.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
38. 38.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a balloon (c) an adult with an iron (d) a cotton bud
40. 40.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) a battery cell (c) a mirror (d) a magnet

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