Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 740 · 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 same cotton bud is what we measure. (a) True (b) False
2. 2.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) paper turns lemony (c) the iron is brown (d) the juice scorches first
3. 3.🧺 Which of these is needed for the secret lemon message? (a) a small bowl (b) a balloon (c) a magnet (d) yeast
4. 4.⚖️ 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
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) yeast (d) white paper
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) a cotton bud (c) white paper (d) a small bowl
7. 7.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) letting the paper dry (c) writing the message (d) reading the message
8. 8.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the iron setting (c) the ironing time (d) the kind of juice
11. 11.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
12. 12.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) turmeric powder (c) a balloon (d) lemon juice
13. 13.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) a rainbow (c) blue words (d) dark brown words
14. 14.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) reading the message (d) ironing the paper
15. 15.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) letting the paper dry (d) dipping the cotton bud
16. 16.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
17. 17.⚖️ 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 measure it (c) we keep it the same
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a cotton bud (d) turmeric powder
19. 19.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
20. 20.True or false: ironing the paper is a job for an adult. (a) False (b) True
21. 21.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) lemon juice (c) a small bowl (d) turmeric powder
23. 23.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) a magnet (d) an adult with an iron
24. 24.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
25. 25.True or false: cutting the lemon is a job for an adult. (a) True (b) False
26. 26.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
27. 27.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
28. 28.True or false: ironing the paper is a job a child can do. (a) True (b) False
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) white paper (c) a small bowl (d) a cotton bud
30. 30.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
31. 31.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
32. 32.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) a cotton bud (c) an adult with an iron (d) a small bowl
34. 34.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) a balloon (d) a cotton bud
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) a balloon (d) a cotton bud
36. 36.⚖️ 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
37. 37.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
38. 38.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) cutting the lemon (d) putting the iron away
39. 39.True or false: plugging in the iron is a job for an adult. (a) False (b) True
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child

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