Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 785 · 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.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) dipping the cotton bud
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a mirror (d) a small bowl
3. 3.True or false: plugging in the iron is a job for an adult. (a) False (b) True
4. 4.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) physical (c) magnetic (d) musical
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we keep it the same (b) we change it (c) we measure it
6. 6.🍋 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) dipping the cotton bud
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) True (b) False
8. 8.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
9. 9.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) plugging in the iron (d) cutting the lemon
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) how dark the writing is (c) the kind of juice (d) the same cotton bud
11. 11.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
12. 12.True or false: turmeric powder is needed for the secret lemon message. (a) False (b) True
13. 13.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) it gets darker (c) writing turns green (d) writing stays faint
14. 14.True or false: ironing the paper is a job for an adult. (a) True (b) False
15. 15.🛟 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
16. 16.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) putting the iron away (d) letting the paper dry
17. 17.⚖️ 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) False (b) True
18. 18.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the iron is brown (c) paper turns lemony (d) the juice scorches first
19. 19.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
20. 20.🛟 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
21. 21.⚖️ 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
22. 22.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
23. 23.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
24. 24.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we measure it (c) we keep it the same
25. 25.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
26. 26.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
27. 27.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a small bowl (c) yeast (d) a mirror
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) True (b) False
29. 29.True or false: a cotton bud is not needed for the secret lemon message. (a) False (b) True
30. 30.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
31. 31.True or false: putting the iron away is a job for an adult. (a) False (b) True
32. 32.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
33. 33.True or false: an adult with an iron is needed for the secret lemon message. (a) False (b) True
34. 34.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
35. 35.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
36. 36.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a battery cell (c) a cotton bud (d) a small bowl
37. 37.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) an adult with an iron (c) a cotton bud (d) a mirror
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
39. 39.True or false: a battery cell is not needed for the secret lemon message. (a) True (b) False
40. 40.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed

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