Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 882 · 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 kept the same. (a) False (b) True
2. 2.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) blue words (c) dark brown words (d) a rainbow
3. 3.🍋 Which of these steps is a job for an adult? (a) writing the message (b) reading the message (c) letting the paper dry (d) ironing the paper
4. 4.🧺 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) a magnet
5. 5.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
6. 6.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) rub your eyes (c) wash your hands (d) lick your fingers
7. 7.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
8. 8.⚖️ 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 kind of juice (c) how dark the writing is (d) the iron setting
9. 9.⚖️ 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 paper
10. 10.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if shaken (c) yes, if cooled (d) yes, in the dark
11. 11.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
12. 12.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a balloon (d) a small bowl
14. 14.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) a magnet (d) an adult with an iron
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
16. 16.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) white (c) green (d) brown
17. 17.True or false: writing the message is a job for an adult. (a) False (b) True
18. 18.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) dipping the cotton bud (d) writing the message
19. 19.🍋 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
20. 20.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
21. 21.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
22. 22.⚖️ 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 change it (c) we measure it
23. 23.⚖️ 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
24. 24.⚖️ 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 kind of juice (c) the same paper (d) the iron setting
25. 25.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) turmeric powder (c) yeast (d) a battery cell
26. 26.🛟 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
27. 27.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
28. 28.True or false: white paper is needed for the secret lemon message. (a) False (b) True
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
30. 30.⚖️ 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
31. 31.⚖️ 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
32. 32.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
33. 33.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a small bowl (d) a cotton bud
35. 35.🧺 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) lemon juice
36. 36.🧺 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) white paper (d) yeast
37. 37.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) lemon juice (c) a battery cell (d) a magnet
38. 38.🍋 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
39. 39.True or false: a balloon is needed for the secret lemon message. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True

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