Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 522 · 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.🧺 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) lemon juice (d) a balloon
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
3. 3.⚖️ 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
4. 4.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
5. 5.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is cold (c) it can burn skin (d) it is magnetic
6. 6.True or false: a small bowl 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) a battery cell (b) lemon juice (c) an adult with an iron (d) a cotton bud
8. 8.🛟 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
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the kind of juice (c) the ironing time (d) the iron setting
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) True (b) False
11. 11.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a balloon (c) a magnet (d) a small bowl
12. 12.⚖️ 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) the ironing time (d) how dark the writing is
13. 13.⚖️ 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
14. 14.🔍 Which is the odd one out? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) cutting the lemon
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) white paper (d) a magnet
16. 16.True or false: ironing the paper is a job a child can do. (a) False (b) True
17. 17.⚖️ 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 same paper (c) how dark the writing is
18. 18.⚖️ 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
19. 19.⚖️ 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 keep it the same (c) we change it
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) white paper (d) a small bowl
21. 21.True or false: white paper is not needed for the secret lemon message. (a) True (b) False
22. 22.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
23. 23.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a small bowl (d) a magnet
24. 24.⚖️ 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
25. 25.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) reading the message
26. 26.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we change it (c) we keep it the same
28. 28.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) blue words (c) almost nothing (d) dark brown words
29. 29.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
30. 30.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) yeast (c) a cotton bud (d) a battery cell
31. 31.🍋 Which of these steps is a job for an adult? (a) writing the message (b) putting the iron away (c) dipping the cotton bud (d) letting the paper dry
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
33. 33.True or false: a small bowl is needed for the secret lemon message. (a) False (b) True
34. 34.🔍 Which is the odd one out? (a) letting the paper dry (b) putting the iron away (c) writing the message (d) reading the message
35. 35.🔮 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
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) yeast (b) white paper (c) a small bowl (d) lemon juice
37. 37.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a balloon (d) white paper
39. 39.True or false: cutting the lemon is a job a child can do. (a) True (b) False
40. 40.⚖️ 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) True (b) False

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