Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 570 · 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 “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
2. 2.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) chemical (c) magnetic (d) physical
3. 3.True or false: writing the message is a job for an adult. (a) False (b) True
4. 4.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
5. 5.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, if cooled (c) no, it stays brown (d) yes, in the dark
6. 6.⚖️ 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
7. 7.True or false: letting the paper dry is a job for an adult. (a) True (b) False
8. 8.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) an adult with an iron (d) turmeric powder
9. 9.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
10. 10.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) yeast (c) an adult with an iron (d) a cotton bud
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) a small bowl (d) a battery cell
12. 12.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) lemon juice (d) a magnet
13. 13.⚖️ 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) how dark the writing is
14. 14.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) blue (c) green (d) white
15. 15.🧺 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 small bowl
16. 16.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
17. 17.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
18. 18.True or false: plugging in the iron 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 “the same cotton bud”? (a) we keep it the same (b) we change it (c) we measure it
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) white paper (c) lemon juice (d) an adult with an iron
21. 21.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
22. 22.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the juice scorches first (d) the iron is brown
23. 23.🔍 Which is the odd one out? (a) ironing the paper (b) plugging in the iron (c) cutting the lemon (d) dipping the cotton bud
24. 24.⚖️ 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
25. 25.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) letting the paper dry (c) ironing the paper (d) plugging in the iron
26. 26.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
27. 27.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
28. 28.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the iron setting (c) how dark the writing is (d) the kind of juice
29. 29.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
30. 30.True or false: plugging in the iron is a job a child can do. (a) False (b) True
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the iron setting (b) the kind of juice (c) how dark the writing is
32. 32.🧺 Do we need yeast for the secret lemon message? (a) needed (b) not needed
33. 33.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
34. 34.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
35. 35.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) dipping the cotton bud (c) cutting the lemon (d) writing the message
36. 36.🔍 Which is the odd one out? (a) cutting the lemon (b) putting the iron away (c) ironing the paper (d) letting the paper dry
37. 37.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) plugging in the iron (d) dipping the cotton bud
38. 38.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) dipping the cotton bud (d) plugging in the iron
39. 39.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
40. 40.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) skip washing (d) lick your fingers

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