8th grade materials and their properties
8th grade (Year 9 in England) · 16 questions · Common Core: NGSS.MS-PS1-2 · England: KS3 Chemistry: Pure and impure substances, KS4 Combined Science: Chemical analysis
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Question 1
In a chromatogram the solvent moved 8 cm and a dye spot moved 1.6 cm from the start line. What is the Rf value of the dye? (Give 2 decimal places.)
Answer
Question 2
How can you test whether a sample of water is pure?
- A. Check that it looks clear
- B. Shake it
- C. Smell it
- D. Check that it boils at exactly 100 °C (at sea-level pressure)
Question 3
Purity and chromatography: which statement is NOT true?
- A. A pure substance has a fixed melting point.
- B. Mixtures can be separated by physical methods.
- C. Air is a mixture of gases.
- D. Impurities have no effect on melting point.
Question 4
In a chromatogram the solvent moved 8 cm and a dye spot moved 4.8 cm from the start line. What is the Rf value of the dye? (Give 2 decimal places.)
Answer
Question 5
An ink gives three separate spots on a chromatogram. What does this show?
- A. The ink is a pure substance
- B. The ink is insoluble
- C. The paper was dirty
- D. The ink is a mixture of at least three dyes
Question 6
Purity and chromatography: which statement is NOT true?
- A. Mixtures can be separated by physical methods.
- B. A pure substance has a fixed melting point.
- C. Orange juice is a pure substance.
- D. Air is a mixture of gases.
Question 7
In a chromatogram the solvent moved 12 cm and a dye spot moved 7.2 cm from the start line. What is the Rf value of the dye? (Give 2 decimal places.)
Answer
Question 8
An ink gives three separate spots on a chromatogram. What does this show?
- A. The paper was dirty
- B. The ink is insoluble
- C. The ink is a pure substance
- D. The ink is a mixture of at least three dyes
Question 9
Purity and chromatography: which statement is NOT true?
- A. Air is a mixture of gases.
- B. In chromatography, a more soluble dye usually travels further.
- C. An Rf value can be greater than 1.
- D. Mixtures can be separated by physical methods.
Question 10
In a chromatogram the solvent moved 12 cm and a dye spot moved 9.6 cm from the start line. What is the Rf value of the dye? (Give 2 decimal places.)
Answer
Question 11
An ink gives three separate spots on a chromatogram. What does this show?
- A. The ink is insoluble
- B. The ink is a mixture of at least three dyes
- C. The ink is a pure substance
- D. The paper was dirty
Question 12
Purity and chromatography: which statement is NOT true?
- A. A pure substance has a fixed melting point.
- B. Mixtures can be separated by physical methods.
- C. Air is a mixture of gases.
- D. An Rf value can be greater than 1.
Question 13
In a chromatogram the solvent moved 6 cm and a dye spot moved 1.2 cm from the start line. What is the Rf value of the dye? (Give 2 decimal places.)
Answer
Question 14
An ink gives three separate spots on a chromatogram. What does this show?
- A. The ink is a mixture of at least three dyes
- B. The ink is insoluble
- C. The paper was dirty
- D. The ink is a pure substance
Question 15
Purity and chromatography: which statement is NOT true?
- A. Air is a mixture of gases.
- B. Impurities have no effect on melting point.
- C. Mixtures can be separated by physical methods.
- D. In chromatography, a more soluble dye usually travels further.
Question 16
In a chromatogram the solvent moved 6 cm and a dye spot moved 1.5 cm from the start line. What is the Rf value of the dye? (Give 2 decimal places.)
Answer
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