Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 792 · 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 ironing time”? (a) we measure it (b) we change it (c) we keep it the same
2. 2.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) no, it stays brown (c) yes, in the dark (d) yes, if cooled
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) yeast (d) an adult with an iron
4. 4.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
5. 5.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) white (d) blue
6. 6.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
7. 7.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
8. 8.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) a mirror
9. 9.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) paper turns lemony (d) the juice scorches first
10. 10.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
11. 11.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
12. 12.True or false: writing the message is a job for an adult. (a) False (b) True
13. 13.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
14. 14.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) ironing the paper (d) reading the message
15. 15.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) letting the paper dry (c) dipping the cotton bud (d) reading the message
16. 16.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) the youngest child (d) any child
17. 17.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) reading the message (d) dipping the cotton bud
18. 18.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) wash your hands (d) rub your eyes
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we keep it the same (c) we measure it
20. 20.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the same cotton bud (d) the same paper
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) False (b) True
22. 22.⚖️ 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
23. 23.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) it turned into air (c) dry juice is see-through (d) the ink is magnetic
25. 25.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a cotton bud (c) a magnet (d) a mirror
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: plugging in the iron is a job for an adult. (a) False (b) True
28. 28.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it is sticky (d) it can burn skin
29. 29.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
30. 30.⚖️ 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
31. 31.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing turns green (d) writing stays faint
32. 32.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a mirror (c) a cotton bud (d) lemon juice
33. 33.⚖️ 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
34. 34.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
35. 35.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
36. 36.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) letting the paper dry (d) cutting the lemon
37. 37.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) reading the message (d) ironing the paper
38. 38.True or false: letting the paper dry is a job for an adult. (a) False (b) True
39. 39.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) reading the message (d) putting the iron away
40. 40.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a battery cell (d) a small bowl

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