Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 981 · 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.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
2. 2.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) white paper (c) a small bowl (d) a cotton bud
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) a balloon (d) a cotton bud
5. 5.True or false: writing the message is a job a child can do. (a) False (b) True
6. 6.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the same paper (c) the kind of juice (d) the same cotton bud
8. 8.True or false: ironing the paper is a job for an adult. (a) True (b) False
9. 9.⚖️ 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 measure it (c) we keep it the same
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a small bowl (c) white paper (d) a cotton bud
11. 11.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
13. 13.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) plugging in the iron (d) cutting the lemon
14. 14.True or false: letting the paper dry is a job a child can do. (a) False (b) True
15. 15.⚖️ 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
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a battery cell (c) an adult with an iron (d) white paper
17. 17.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
18. 18.🔍 Which is the odd one out? (a) writing the message (b) plugging in the iron (c) dipping the cotton bud (d) letting the paper dry
19. 19.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) letting the paper dry
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) turmeric powder (d) white paper
21. 21.⚖️ 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) the kind of juice (c) how dark the writing is
22. 22.True or false: a small bowl is needed for the secret lemon message. (a) True (b) False
23. 23.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
24. 24.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
25. 25.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) reading the message (d) plugging in the iron
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
27. 27.True or false: cutting the lemon is a job a child can do. (a) True (b) False
28. 28.⚖️ 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 iron setting
29. 29.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) green (d) brown
30. 30.⚖️ 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 change it (c) we measure it
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a magnet (c) yeast (d) turmeric powder
32. 32.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) chemical (d) magnetic
33. 33.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) the iron is brown (d) heat adds colour
34. 34.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
35. 35.⚖️ 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) True (b) False
36. 36.⚖️ 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 kind of juice (c) the same cotton bud (d) the iron setting
37. 37.⚖️ 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
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
39. 39.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it can burn skin (d) it is sticky
40. 40.⚖️ 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 measure it (c) we change it

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