Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 334 · 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.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
2. 2.⚖️ 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
3. 3.True or false: putting the iron away is a job for an adult. (a) False (b) True
4. 4.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) a battery cell (c) lemon juice (d) an adult with an iron
5. 5.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
6. 6.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) letting the paper dry (d) ironing the paper
7. 7.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a magnet (c) a battery cell (d) white paper
8. 8.⚖️ 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
9. 9.⚖️ 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 iron setting (c) the same cotton bud (d) the same paper
10. 10.⚖️ 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
11. 11.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
12. 12.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) letting the paper dry (d) cutting the lemon
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
14. 14.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
15. 15.⚖️ 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 measure it (c) we change it
16. 16.🍋 Which of these steps is a job for an adult? (a) reading the message (b) ironing the paper (c) writing the message (d) dipping the cotton bud
17. 17.True or false: putting the iron away is a job a child can do. (a) True (b) False
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) lemon juice (d) yeast
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
20. 20.True or false: ironing the paper is a job a child can do. (a) False (b) True
21. 21.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a magnet (c) a battery cell (d) a small bowl
22. 22.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) it gets darker (d) the paper floats
23. 23.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) the juice scorches first (c) heat adds colour (d) the iron is brown
24. 24.⚖️ 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
25. 25.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
26. 26.True or false: plugging in the iron is a job a child can do. (a) False (b) True
27. 27.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
28. 28.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
29. 29.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
30. 30.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a magnet (c) lemon juice (d) an adult with an iron
31. 31.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) yeast (c) a magnet (d) a balloon
32. 32.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) brown (c) blue (d) white
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a mirror (d) a small bowl
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a mirror (d) a cotton bud
35. 35.True or false: reading the message is a job a child can do. (a) True (b) False
36. 36.True or false: letting the paper dry is a job a child can do. (a) True (b) False
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) an adult with an iron (c) a cotton bud (d) white paper
38. 38.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
39. 39.True or false: plugging in the iron is a job for an adult. (a) False (b) True
40. 40.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) whoever is fastest (d) only an adult

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