Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 94 · 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? Which of these is what we measure? (a) the same cotton bud (b) the ironing time (c) the iron setting (d) how dark the writing is
2. 2.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
3. 3.True or false: reading the message is a job for an adult. (a) False (b) True
4. 4.⚖️ 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
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same
6. 6.🔍 Which is the odd one out? (a) cutting the lemon (b) writing the message (c) dipping the cotton bud (d) letting the paper dry
7. 7.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) brown (d) green
8. 8.True or false: writing the message is a job a child can do. (a) False (b) True
9. 9.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
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 kind of juice (c) the ironing time (d) how dark the writing is
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) how dark the writing is (c) the kind of juice
12. 12.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
13. 13.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
14. 14.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) only an adult (c) the youngest child (d) whoever is fastest
15. 15.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) rub your eyes (d) wash your hands
16. 16.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
17. 17.⚖️ 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
18. 18.🛟 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
19. 19.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) putting the iron away (d) letting the paper dry
20. 20.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) ironing the paper (d) dipping the cotton bud
21. 21.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) a rainbow (c) dark brown words (d) almost nothing
22. 22.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
23. 23.⚖️ 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) False (b) True
24. 24.🔮 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
25. 25.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
26. 26.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) plugging in the iron (d) writing the message
27. 27.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) dry juice is see-through (c) it turned into air (d) the ink is magnetic
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) a small bowl (d) a magnet
29. 29.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a magnet (c) an adult with an iron (d) a balloon
30. 30.🧺 Do we need a mirror 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 ironing time”? (a) we keep it the same (b) we measure it (c) we change it
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) a small bowl (d) an adult with an iron
33. 33.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a cotton bud (c) a magnet (d) a small bowl
35. 35.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
37. 37.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
38. 38.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
39. 39.⚖️ 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 measure it (c) we change it
40. 40.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed

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