Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 672 · 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? True or false: the kind of juice is what we measure. (a) True (b) False
2. 2.🛟 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
3. 3.🔍 Which is the odd one out? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) dipping the cotton bud
4. 4.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) yeast (c) lemon juice (d) a mirror
5. 5.⚖️ 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
6. 6.🔍 Which is the odd one out? (a) putting the iron away (b) writing the message (c) ironing the paper (d) plugging in the iron
7. 7.⚖️ 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) the kind of juice (c) the same paper (d) the same cotton bud
8. 8.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) putting the iron away (d) cutting the lemon
9. 9.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) physical (c) chemical (d) magnetic
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a magnet (d) an adult with an iron
11. 11.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) a balloon (d) yeast
12. 12.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
13. 13.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
14. 14.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) cutting the lemon (d) dipping the cotton bud
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
16. 16.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
17. 17.True or false: lemon juice is not needed for the secret lemon message. (a) False (b) True
18. 18.True or false: reading the message is a job for an adult. (a) False (b) True
19. 19.⚖️ 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
20. 20.True or false: lemon juice is needed for the secret lemon message. (a) True (b) False
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
22. 22.True or false: a battery cell is needed for the secret lemon message. (a) True (b) False
23. 23.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) the iron is brown (c) paper turns lemony (d) heat adds colour
24. 24.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
25. 25.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) yes, in the dark (d) no, it stays brown
26. 26.True or false: letting the paper dry is a job a child can do. (a) True (b) False
27. 27.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
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 change it (b) we keep it the same (c) we measure it
29. 29.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the iron setting (c) the same cotton bud (d) the ironing time
31. 31.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) letting the paper dry
32. 32.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) putting the iron away (d) ironing the paper
33. 33.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) lick your fingers (c) wash your hands (d) skip washing
34. 34.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) putting the iron away (c) ironing the paper (d) letting the paper dry
35. 35.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a cotton bud (c) yeast (d) an adult with an iron
37. 37.True or false: putting the iron away is a job for an adult. (a) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
39. 39.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) the paper ate it (c) the ink is magnetic (d) dry juice is see-through
40. 40.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it is sticky (d) it can burn skin

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