Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 535 · 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.🍋 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
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) white paper (d) turmeric powder
3. 3.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) putting the iron away (d) cutting the lemon
4. 4.🔍 Which is the odd one out? (a) reading the message (b) plugging in the iron (c) letting the paper dry (d) dipping the cotton bud
5. 5.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) dipping the cotton bud (d) cutting the lemon
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) lemon juice (d) a magnet
7. 7.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) writing turns green (c) it gets darker (d) the paper floats
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) white paper (d) a cotton bud
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a cotton bud (c) an adult with an iron (d) lemon juice
10. 10.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the kind of juice (c) the same paper (d) the ironing time
12. 12.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) dark brown words (d) almost nothing
13. 13.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) False (b) True
15. 15.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, in the dark (d) yes, if cooled
16. 16.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) reading the message (d) plugging in the iron
17. 17.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a battery cell (d) a magnet
18. 18.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it can burn skin (d) it is cold
19. 19.⚖️ 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) False (b) True
20. 20.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
21. 21.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
22. 22.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
23. 23.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a balloon (d) a cotton bud
24. 24.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
25. 25.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) a small bowl (c) lemon juice (d) an adult with an iron
26. 26.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
27. 27.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) whoever is fastest (d) only an adult
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
29. 29.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
30. 30.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we keep it the same (c) we measure it
32. 32.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
33. 33.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) reading the message (d) cutting the lemon
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a balloon (b) lemon juice (c) a small bowl (d) an adult with an iron
35. 35.🍋 Which of these steps is a job a child can do? (a) writing the message (b) cutting the lemon (c) ironing the paper (d) plugging in the iron
36. 36.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
37. 37.⚖️ 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
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) magnetic (d) chemical
39. 39.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) writing the message (d) putting the iron away
40. 40.⚖️ 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

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