Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 636 · 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: reading the message is a job for an adult. (a) True (b) False
2. 2.True or false: ironing the paper is a job a child can do. (a) True (b) False
3. 3.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) yes, if shaken (d) no, it stays brown
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) False (b) True
5. 5.⚖️ 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
6. 6.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
7. 7.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) the juice scorches first (d) paper turns lemony
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
9. 9.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
10. 10.⚖️ 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) the iron setting (d) how dark the writing is
11. 11.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) reading the message (d) ironing the paper
12. 12.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) dipping the cotton bud
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) False (b) True
14. 14.🔮 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
15. 15.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
16. 16.⚖️ 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
17. 17.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) dipping the cotton bud (c) plugging in the iron (d) ironing the paper
18. 18.⚖️ 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 cotton bud
19. 19.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
20. 20.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
21. 21.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) writing the message (d) letting the paper dry
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we keep it the same (b) we measure it (c) we change it
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) white paper (c) lemon juice (d) a small bowl
24. 24.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
25. 25.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) turmeric powder (c) a small bowl (d) a battery cell
27. 27.True or false: putting the iron away is a job a child can do. (a) True (b) False
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) how dark the writing is (c) the same paper (d) the kind of juice
29. 29.True or false: letting the paper dry is a job a child can do. (a) False (b) True
30. 30.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) turmeric powder (d) lemon juice
31. 31.🛟 Why must children keep their fingers away from the iron? (a) it can burn skin (b) it is cold (c) it is sticky (d) it is magnetic
32. 32.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
33. 33.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) letting the paper dry
34. 34.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
35. 35.⚖️ 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 iron setting (c) how dark the writing is
36. 36.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
37. 37.⚖️ 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
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) a small bowl (d) a balloon
39. 39.True or false: an adult with an iron is not needed for the secret lemon message. (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) False (b) True

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