Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 70 · 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.🔍 Which is the odd one out? (a) dipping the cotton bud (b) reading the message (c) ironing the paper (d) writing the message
2. 2.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) writing the message (d) cutting the lemon
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) an adult with an iron (d) a magnet
4. 4.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) cutting the lemon (c) plugging in the iron (d) writing the message
5. 5.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) whoever is fastest (d) any child
6. 6.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, in the dark (c) yes, if cooled (d) yes, if shaken
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) white paper (c) an adult with an iron (d) yeast
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a mirror (c) white paper (d) a small bowl
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
10. 10.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) yeast (d) a battery cell
12. 12.⚖️ 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
13. 13.⚖️ 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) how dark the writing is (c) the kind of juice (d) the ironing time
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is sticky (d) it is magnetic
15. 15.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
16. 16.True or false: reading the message is a job a child can do. (a) False (b) True
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we measure it (c) we change it
18. 18.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) white paper (c) an adult with an iron (d) a cotton bud
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) white paper (d) turmeric powder
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) turmeric powder (c) yeast (d) white paper
23. 23.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
24. 24.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
25. 25.⚖️ 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) how dark the writing is (c) the same cotton bud
26. 26.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a cotton bud (d) a battery cell
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
29. 29.True or false: cutting the lemon is a job a child can do. (a) False (b) True
30. 30.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) lick your fingers (d) wash your hands
31. 31.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
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 ironing time is what we measure. (a) True (b) False
34. 34.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
35. 35.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
36. 36.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
37. 37.True or false: letting the paper dry is a job for an adult. (a) False (b) True
38. 38.🍋 Which of these steps is a job a child can do? (a) reading the message (b) cutting the lemon (c) ironing the paper (d) putting the iron away
39. 39.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the same paper (c) how dark the writing is (d) the kind of juice

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