Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 864 · 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.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) green (c) white (d) brown
2. 2.🧺 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) lemon juice
3. 3.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) a magnet (c) a cotton bud (d) lemon juice
4. 4.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
5. 5.⚖️ 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 measure it (c) we keep it the same
6. 6.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a magnet (c) yeast (d) a small bowl
7. 7.🍋 Which of these steps is a job for an adult? (a) writing the message (b) dipping the cotton bud (c) cutting the lemon (d) reading the message
8. 8.⚖️ 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 measure it (c) we change it
9. 9.True or false: turmeric powder is not needed for the secret lemon message. (a) True (b) False
10. 10.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
11. 11.⚖️ 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
12. 12.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) a battery cell (c) yeast (d) a mirror
13. 13.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) lemon juice (d) white paper
14. 14.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) letting the paper dry (c) plugging in the iron (d) ironing the paper
15. 15.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
16. 16.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
17. 17.True or false: dipping the cotton bud is a job for an adult. (a) True (b) False
18. 18.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) only an adult (d) whoever is fastest
19. 19.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) skip washing (d) wash your hands
20. 20.⚖️ 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
21. 21.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
22. 22.True or false: writing the message is a job for an adult. (a) False (b) True
23. 23.True or false: letting the paper dry is a job a child can do. (a) False (b) True
24. 24.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) putting the iron away (c) reading the message (d) letting the paper dry
25. 25.⚖️ 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) False (b) True
26. 26.⚖️ 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 paper
27. 27.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
28. 28.🧺 Do we need a mirror for the secret lemon message? (a) not needed (b) needed
29. 29.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) heat adds colour (c) the iron is brown (d) paper turns lemony
30. 30.🧺 Do we need a balloon for the secret lemon message? (a) needed (b) not needed
31. 31.True or false: cutting the lemon is a job for an adult. (a) False (b) True
32. 32.⚖️ 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
33. 33.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it is magnetic (d) it can burn skin
34. 34.⚖️ 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 measure it (c) we change it
35. 35.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) plugging in the iron (c) dipping the cotton bud (d) putting the iron away
36. 36.🔍 Which is the odd one out? (a) plugging in the iron (b) letting the paper dry (c) ironing the paper (d) cutting the lemon
37. 37.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a small bowl (c) yeast (d) an adult with an iron
38. 38.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
39. 39.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a mirror (b) lemon juice (c) a cotton bud (d) an adult with an iron
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we change it (c) we keep it the same

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