Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 237 · 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? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
2. 2.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) dipping the cotton bud (d) ironing the paper
3. 3.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it can burn skin (c) it is sticky (d) it is magnetic
4. 4.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a balloon (c) a small bowl (d) turmeric powder
5. 5.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
6. 6.True or false: ironing the paper is a job for an adult. (a) False (b) True
7. 7.⚖️ 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) the iron setting (d) how dark the writing is
8. 8.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
9. 9.True or false: an adult with an iron is not needed for the secret lemon message. (a) False (b) True
10. 10.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) ironing the paper (d) letting the paper dry
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 iron setting (c) the same paper (d) the kind of juice
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a mirror (c) a cotton bud (d) lemon juice
13. 13.⚖️ 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
14. 14.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
15. 15.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) white paper (c) a small bowl (d) lemon juice
17. 17.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
18. 18.🔍 Which is the odd one out? (a) dipping the cotton bud (b) putting the iron away (c) letting the paper dry (d) reading the message
19. 19.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) writing the message (d) plugging in the iron
20. 20.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) lemon juice (d) a magnet
23. 23.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
24. 24.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
25. 25.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) wash your hands (d) skip washing
26. 26.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
27. 27.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
28. 28.True or false: ironing the paper is a job a child can do. (a) True (b) False
29. 29.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
30. 30.True or false: letting the paper dry is a job a child can do. (a) False (b) True
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) lemon juice (d) an adult with an iron
32. 32.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
34. 34.🍋 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
35. 35.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) any child (d) whoever is fastest
36. 36.⚖️ 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
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
38. 38.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
39. 39.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
40. 40.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) putting the iron away (d) writing the message

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