Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 809 · 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.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) chemical (d) physical
2. 2.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
3. 3.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) reading the message (d) ironing the paper
4. 4.⚖️ 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
5. 5.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) yeast (c) lemon juice (d) a cotton bud
6. 6.True or false: plugging in the iron is a job for an adult. (a) False (b) True
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) an adult with an iron (d) a battery cell
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) brown (d) blue
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) a mirror (d) a cotton bud
10. 10.🔮 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
11. 11.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
12. 12.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a balloon (d) white paper
14. 14.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) a rainbow (d) dark brown words
15. 15.🛟 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
16. 16.⚖️ 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 paper
17. 17.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
18. 18.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) True (b) False
20. 20.⚖️ 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 same cotton bud (c) the kind of juice (d) how dark the writing is
21. 21.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
22. 22.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
23. 23.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we change it (b) we keep it the same (c) we measure it
24. 24.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) cutting the lemon (d) dipping the cotton bud
25. 25.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing stays faint (d) writing turns green
26. 26.🍋 Why can’t you see the lemon writing once it dries? (a) the ink is magnetic (b) dry juice is see-through (c) the paper ate it (d) it turned into air
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) white paper (d) a mirror
28. 28.⚖️ 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 change it (c) we keep it the same
29. 29.True or false: white paper is needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ 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 same cotton bud (c) the iron setting (d) the ironing time
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we keep it the same (b) we change it (c) we measure it
32. 32.⚖️ 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
33. 33.True or false: cutting the lemon is a job a child can do. (a) True (b) False
34. 34.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
35. 35.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) the youngest child (c) any child (d) only an adult
36. 36.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) putting the iron away (d) ironing the paper
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a small bowl (c) a cotton bud (d) white paper
38. 38.⚖️ 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
39. 39.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
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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