Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 879 · 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.True or false: plugging in the iron is a job a child can do. (a) True (b) False
2. 2.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) plugging in the iron (d) dipping the cotton bud
3. 3.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) a rainbow (d) dark brown words
4. 4.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
5. 5.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) the juice scorches first (c) paper turns lemony (d) heat adds colour
6. 6.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) a cotton bud (d) white paper
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
9. 9.🔍 Which is the odd one out? (a) putting the iron away (b) dipping the cotton bud (c) writing the message (d) reading the message
10. 10.🍋 Which of these steps is a job a child can do? (a) reading the message (b) ironing the paper (c) putting the iron away (d) plugging in the iron
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the iron setting (c) how dark the writing is (d) the same cotton bud
12. 12.🛟 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
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) whoever is fastest (c) any child (d) the youngest child
14. 14.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) True (b) False
16. 16.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a small bowl (d) yeast
17. 17.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
18. 18.⚖️ 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
19. 19.⚖️ 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) True (b) False
20. 20.⚖️ 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
21. 21.🔍 Which is the odd one out? (a) writing the message (b) cutting the lemon (c) reading the message (d) letting the paper dry
22. 22.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) plugging in the iron (d) dipping the cotton bud
23. 23.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a small bowl (d) turmeric powder
24. 24.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
25. 25.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) dipping the cotton bud (d) reading the message
26. 26.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
27. 27.⚖️ 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
28. 28.True or false: cutting the lemon is a job for an adult. (a) True (b) False
29. 29.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
30. 30.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
31. 31.True or false: letting the paper dry is a job a child can do. (a) True (b) False
32. 32.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
33. 33.True or false: ironing the paper is a job for an adult. (a) True (b) False
34. 34.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
35. 35.⚖️ 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
36. 36.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
37. 37.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
38. 38.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) turmeric powder (c) a magnet (d) a cotton bud
39. 39.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the ironing time

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