Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 760 · 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 ironing time is the one thing we change. (a) True (b) False
2. 2.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
3. 3.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the ink is magnetic (c) the paper ate it (d) dry juice is see-through
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
5. 5.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
6. 6.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
7. 7.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) the youngest child (d) only an adult
8. 8.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
9. 9.⚖️ 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
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) the iron setting (c) the ironing time (d) the same paper
11. 11.🍋 Secret message: who does this step — writing the message? (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? Which of these is what we measure? (a) the kind of juice (b) how dark the writing is (c) the iron setting (d) the ironing time
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a mirror (c) lemon juice (d) a cotton bud
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) lemon juice (d) a mirror
16. 16.🍋 Which of these steps is a job a child can do? (a) writing the message (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
17. 17.🔍 Which is the odd one out? (a) writing the message (b) letting the paper dry (c) dipping the cotton bud (d) ironing the paper
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a balloon (c) white paper (d) an adult with an iron
19. 19.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) almost nothing (c) blue words (d) dark brown words
20. 20.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) the juice scorches first (d) paper turns lemony
21. 21.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) putting the iron away (d) dipping the cotton bud
22. 22.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
23. 23.🍋 Which of these steps is a job for an adult? (a) reading the message (b) putting the iron away (c) dipping the cotton bud (d) letting the paper dry
24. 24.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) writing the message (d) ironing the paper
25. 25.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
26. 26.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) plugging in the iron (d) reading the message
27. 27.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
28. 28.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) plugging in the iron (d) reading the message
29. 29.⚖️ 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
30. 30.⚖️ 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
31. 31.True or false: writing the message is a job for an adult. (a) True (b) False
32. 32.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
33. 33.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
34. 34.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
35. 35.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
36. 36.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
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) True (b) False
38. 38.True or false: yeast is not needed for the secret lemon message. (a) False (b) True
39. 39.True or false: an adult with an iron is not needed for the secret lemon message. (a) True (b) False
40. 40.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False

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