Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 286 · 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 of these is not needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) an adult with an iron (d) white paper
2. 2.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) dipping the cotton bud
3. 3.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) the paper floats (c) it gets darker (d) writing stays faint
6. 6.⚖️ 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
7. 7.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) turmeric powder (d) lemon juice
9. 9.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
10. 10.⚖️ 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
11. 11.⚖️ 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 ironing time
12. 12.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
13. 13.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
14. 14.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
15. 15.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) paper turns lemony (c) heat adds colour (d) the juice scorches first
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
17. 17.🔍 Which is the odd one out? (a) plugging in the iron (b) cutting the lemon (c) ironing the paper (d) writing the message
18. 18.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
19. 19.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) a cotton bud (d) a magnet
20. 20.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we change it (c) we measure it
22. 22.⚖️ 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 same cotton bud (d) the iron setting
23. 23.🧺 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 magnet (d) white paper
24. 24.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
25. 25.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) putting the iron away (d) ironing the paper
26. 26.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
27. 27.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
28. 28.🔍 Which is the odd one out? (a) ironing the paper (b) reading the message (c) cutting the lemon (d) putting the iron away
29. 29.True or false: yeast is needed for the secret lemon message. (a) True (b) False
30. 30.🍋 Which of these steps is a job a child can do? (a) reading the message (b) ironing the paper (c) putting the iron away (d) cutting the lemon
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the kind of juice (c) how dark the writing is (d) the same cotton bud
32. 32.True or false: reading the message is a job a child can do. (a) True (b) False
33. 33.⚖️ 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) True (b) False
34. 34.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is sticky (d) it is cold
35. 35.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a cotton bud (c) a balloon (d) a small bowl
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.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
38. 38.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
39. 39.🔍 Which is the odd one out? (a) reading the message (b) dipping the cotton bud (c) putting the iron away (d) writing the message
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) lemon juice (c) an adult with an iron (d) a small bowl

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