Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 750 · 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? Which of these is the one thing we change? (a) the same cotton bud (b) the iron setting (c) the kind of juice (d) the same paper
2. 2.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) a small bowl (d) lemon juice
4. 4.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
5. 5.⚖️ 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
6. 6.⚖️ 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) True (b) False
7. 7.True or false: putting the iron away is a job for an adult. (a) True (b) False
8. 8.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) turmeric powder (d) lemon juice
10. 10.⚖️ 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 change it (c) we measure it
11. 11.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
12. 12.🍋 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
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
14. 14.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
15. 15.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is sticky (d) it is magnetic
16. 16.⚖️ 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) how dark the writing is (d) the kind of juice
17. 17.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
18. 18.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) white paper (c) a cotton bud (d) lemon juice
19. 19.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) dipping the cotton bud (d) letting the paper dry
20. 20.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
21. 21.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
22. 22.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
23. 23.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
24. 24.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) reading the message (d) cutting the lemon
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) white paper (c) lemon juice (d) a mirror
26. 26.True or false: ironing the paper is a job for an adult. (a) True (b) False
27. 27.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
28. 28.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a balloon (c) yeast (d) a magnet
29. 29.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
31. 31.🔍 Which is the odd one out? (a) letting the paper dry (b) ironing the paper (c) reading the message (d) dipping the cotton bud
32. 32.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
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) the ironing time (c) how dark the writing is
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) only an adult (c) any child (d) the youngest child
35. 35.⚖️ 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 keep it the same (c) we change it
36. 36.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) writing stays faint (d) the paper floats
37. 37.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) skip washing (d) wash your hands
38. 38.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) plugging in the iron (d) putting the iron away
39. 39.True or false: a small bowl is not needed for the secret lemon message. (a) True (b) False
40. 40.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False

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