Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 42 · 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) an adult with an iron (b) lemon juice (c) a cotton bud (d) a balloon
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a battery cell (d) white paper
3. 3.🛟 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
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we change it (b) we keep it the same (c) we measure it
5. 5.True or false: writing the message is a job for an adult. (a) False (b) True
6. 6.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a cotton bud (c) a balloon (d) white paper
7. 7.🔍 Which is the odd one out? (a) dipping the cotton bud (b) plugging in the iron (c) letting the paper dry (d) writing the message
8. 8.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is cold (d) it is sticky
9. 9.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) a battery cell (d) white paper
10. 10.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
11. 11.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
13. 13.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) how dark the writing is (c) the kind of juice
15. 15.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) heat adds colour (d) paper turns lemony
16. 16.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) a small bowl (d) a balloon
17. 17.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
18. 18.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
19. 19.🧺 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) a mirror
20. 20.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
21. 21.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) white paper (d) a magnet
22. 22.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) ironing the paper (d) plugging in the iron
23. 23.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) letting the paper dry (d) writing the message
24. 24.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) plugging in the iron (c) cutting the lemon (d) writing the message
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
26. 26.⚖️ 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 same paper (d) the same cotton bud
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) it gets darker (d) writing stays faint
28. 28.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
29. 29.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
30. 30.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) blue words (c) a rainbow (d) almost nothing
31. 31.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
32. 32.True or false: cutting the lemon is a job a child can do. (a) True (b) False
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the same cotton bud (c) how dark the writing is (d) the ironing time
34. 34.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) physical (d) chemical
35. 35.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
37. 37.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
38. 38.True or false: cutting the lemon is a job for an adult. (a) True (b) False
39. 39.True or false: plugging in the iron is a job a child can do. (a) False (b) True
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we measure it (c) we change it

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