Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 666 · 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) any child (b) whoever is fastest (c) the youngest child (d) only an adult
2. 2.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) almost nothing (d) a rainbow
3. 3.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
4. 4.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) reading the message
5. 5.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) reading the message (c) putting the iron away (d) ironing the paper
6. 6.🔮 Predict: the adult irons for only one second. What happens? (a) writing stays faint (b) it gets darker (c) writing turns green (d) the paper floats
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we change it (c) we measure it
9. 9.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
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 same paper (b) the same cotton bud (c) the kind of juice (d) how dark the writing is
11. 11.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
12. 12.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
13. 13.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) reading the message (d) ironing the paper
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the ironing time (b) the kind of juice (c) how dark the writing is
16. 16.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) an adult with an iron (c) turmeric powder (d) a mirror
17. 17.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) dipping the cotton bud (d) cutting the lemon
18. 18.True or false: a balloon is needed for the secret lemon message. (a) False (b) True
19. 19.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
20. 20.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
21. 21.🔮 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
22. 22.True or false: letting the paper dry is a job for an adult. (a) True (b) False
23. 23.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) magnetic (d) chemical
24. 24.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) a cotton bud (d) a battery cell
25. 25.⚖️ 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 iron setting (c) the kind of juice
26. 26.⚖️ 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
27. 27.⚖️ 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 same paper (c) the kind of juice
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) lemon juice (c) an adult with an iron (d) yeast
29. 29.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a battery cell (c) white paper (d) an adult with an iron
31. 31.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) letting the paper dry (d) plugging in the iron
32. 32.🧺 Which of these is needed for the secret lemon message? (a) white paper (b) yeast (c) a battery cell (d) a magnet
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) lemon juice (d) white paper
34. 34.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a balloon (c) a cotton bud (d) an adult with an iron
36. 36.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) writing the message (d) reading the message
37. 37.True or false: putting the iron away is a job for an adult. (a) True (b) False
38. 38.⚖️ 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
39. 39.True or false: cutting the lemon is a job a child can do. (a) False (b) True
40. 40.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False

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