Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 293 · 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.⚖️ 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
2. 2.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) True (b) False
3. 3.🔍 Which is the odd one out? (a) ironing the paper (b) dipping the cotton bud (c) putting the iron away (d) plugging in the iron
4. 4.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
5. 5.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) a balloon (d) an adult with an iron
6. 6.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
7. 7.📘 The browning of lemon juice with heat is a ___ change. (a) magnetic (b) musical (c) chemical (d) physical
8. 8.🧺 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) a balloon (d) a cotton bud
9. 9.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
10. 10.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) turmeric powder (b) a small bowl (c) an adult with an iron (d) white paper
12. 12.⚖️ 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 measure it (c) we change it
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
14. 14.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) yeast
15. 15.True or false: yeast is needed for the secret lemon message. (a) False (b) True
16. 16.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the iron setting (c) how dark the writing is (d) the kind of juice
18. 18.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) cutting the lemon (d) ironing the paper
19. 19.True or false: a battery cell is not needed for the secret lemon message. (a) False (b) True
20. 20.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
21. 21.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
22. 22.🛟 Who should use the hot iron in the secret message experiment? (a) whoever is fastest (b) any child (c) only an adult (d) the youngest child
23. 23.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
24. 24.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
25. 25.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
26. 26.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
27. 27.🛟 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
28. 28.🧺 Do we need an adult with an iron for the secret lemon message? (a) needed (b) not needed
29. 29.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
30. 30.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
31. 31.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) reading the message (c) ironing the paper (d) putting the iron away
32. 32.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
33. 33.True or false: plugging in the iron is a job a child can do. (a) False (b) True
34. 34.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
35. 35.True or false: ironing the paper is a job a child can do. (a) False (b) True
36. 36.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) cutting the lemon (d) ironing the paper
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) a battery cell (d) an adult with an iron
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
39. 39.⚖️ 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
40. 40.True or false: white paper is needed for the secret lemon message. (a) True (b) False

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