Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 922 · 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: ironing the paper is a job for an adult. (a) False (b) True
2. 2.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
3. 3.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) an adult with an iron (c) a small bowl (d) lemon juice
5. 5.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
6. 6.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
7. 7.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
8. 8.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
9. 9.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
11. 11.True or false: white paper is needed for the secret lemon message. (a) True (b) False
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a magnet (d) white paper
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the same paper (c) the kind of juice (d) how dark the writing is
14. 14.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) letting the paper dry (d) reading the message
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) dry juice is see-through (d) the ink is magnetic
16. 16.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) reading the message (d) plugging in the iron
17. 17.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a balloon (c) a battery cell (d) white paper
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
19. 19.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) ironing the paper (c) putting the iron away (d) plugging in the iron
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) white paper (d) lemon juice
21. 21.🧺 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 cotton bud (d) a balloon
22. 22.True or false: cutting the lemon is a job for an adult. (a) True (b) False
23. 23.⚖️ 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 keep it the same (c) we measure it
24. 24.True or false: a magnet is not needed for the secret lemon message. (a) True (b) False
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
26. 26.⚖️ 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
27. 27.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) a mirror (d) a small bowl
28. 28.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
29. 29.True or false: cutting the lemon is a job a child can do. (a) False (b) True
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) an adult with an iron (d) lemon juice
31. 31.⚖️ 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
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
33. 33.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
34. 34.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
35. 35.True or false: letting the paper dry is a job a child can do. (a) False (b) True
36. 36.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it is magnetic (d) it can burn skin
37. 37.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) dipping the cotton bud (d) putting the iron away
38. 38.True or false: writing the message is a job a child can do. (a) True (b) False
39. 39.True or false: plugging in the iron is a job for an adult. (a) False (b) True
40. 40.⚖️ 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) how dark the writing is (d) the same cotton bud

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