Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 801 · 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.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) heat adds colour (d) the iron is brown
2. 2.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) a battery cell (d) a cotton bud
3. 3.True or false: a cotton bud is needed for the secret lemon message. (a) False (b) True
4. 4.🧺 Which of these is needed for the secret lemon message? (a) an adult with an iron (b) turmeric powder (c) a magnet (d) yeast
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
6. 6.⚖️ 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
7. 7.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
8. 8.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) cutting the lemon
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) lick your fingers (d) skip washing
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
11. 11.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
12. 12.🔍 Which is the odd one out? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) letting the paper dry
13. 13.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a cotton bud (c) a balloon (d) white paper
15. 15.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
16. 16.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
17. 17.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
18. 18.⚖️ 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 same paper (c) how dark the writing is (d) the ironing time
19. 19.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a magnet (d) a small bowl
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) False (b) True
21. 21.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) cutting the lemon (d) letting the paper dry
22. 22.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
23. 23.🧺 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
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
25. 25.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
26. 26.⚖️ 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 change it (c) we keep it the same
27. 27.True or false: white paper is needed for the secret lemon message. (a) True (b) False
28. 28.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
29. 29.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
30. 30.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
31. 31.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
32. 32.True or false: ironing the paper is a job a child can do. (a) False (b) True
33. 33.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a mirror (c) yeast (d) a small bowl
34. 34.True or false: writing the message is a job a child can do. (a) False (b) True
35. 35.🔮 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
36. 36.🍋 Which of these steps is a job for an adult? (a) writing the message (b) plugging in the iron (c) reading the message (d) dipping the cotton bud
37. 37.⚖️ 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 change it (c) we measure it
38. 38.True or false: letting the paper dry is a job a child can do. (a) False (b) True
39. 39.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
40. 40.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False

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