Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 798 · 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? Which of these is what we measure? (a) how dark the writing is (b) the same cotton bud (c) the same paper (d) the iron setting
2. 2.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
3. 3.True or false: reading the message is a job for an adult. (a) True (b) False
4. 4.🍋 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
5. 5.🧺 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) a cotton bud (d) yeast
6. 6.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is sticky (c) it is cold (d) it can burn skin
7. 7.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a small bowl (c) yeast (d) a battery cell
9. 9.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
10. 10.True or false: putting the iron away is a job for an adult. (a) False (b) True
11. 11.True or false: writing the message is a job a child can do. (a) False (b) True
12. 12.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) plugging in the iron (d) reading the message
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
14. 14.⚖️ 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
15. 15.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) the paper ate it (d) it turned into air
16. 16.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) chemical (d) musical
17. 17.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) an adult with an iron (c) lemon juice (d) a cotton bud
18. 18.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
19. 19.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
20. 20.True or false: a magnet is not needed for the secret lemon message. (a) False (b) True
21. 21.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) ironing the paper (d) dipping the cotton bud
22. 22.⚖️ 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 same paper (c) the iron setting (d) the ironing time
23. 23.⚖️ 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 change it (c) we measure it
24. 24.🧺 Do we need a cotton bud for the secret lemon message? (a) needed (b) not needed
25. 25.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
26. 26.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) a mirror (c) a balloon (d) white paper
27. 27.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) yeast (c) lemon juice (d) an adult with an iron
28. 28.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) plugging in the iron (c) cutting the lemon (d) ironing the paper
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) writing the message
30. 30.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
31. 31.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) ironing the paper (c) plugging in the iron (d) reading the message
32. 32.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
33. 33.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
34. 34.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
35. 35.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) a battery cell (d) an adult with an iron
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we measure it (b) we keep it the same (c) we change it
37. 37.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) turmeric powder (c) an adult with an iron (d) a mirror
38. 38.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
39. 39.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
40. 40.True or false: cutting the lemon is a job a child can do. (a) False (b) True

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