CBSE Class 8 Science Nature of Matter Elements, Compounds, and Mixtures (Class 8 NCERT New) Quiz 6

1. Which statement identifies why oxygen is classified as a pure substance and air is classified as a mixture?

A Oxygen is more reactive than air. B Oxygen has a higher density than air. C Oxygen goes under a phase change, whereas air is always a gas. D Oxygen contains only one substance, but air contains several substances.

2. Which of the following is an example of of a container filled with a pure substance rather than with a mixture?

A A tire filled with air. B A jar filled with salt water. C A balloon filled with helium. D A glass filled with chocolate milk.

3. When electricity passes through water, hydrogen and oxygen are produced. Which table correctly labels the compounds and elements involved in the process?

A Water-->CompoundHydrogen-->CompoundOxygen--->Element B Water-->CompoundHydrogen--->ElementOxygen--->Compound C Water--->CompoundHydrogen--->ElementOxygen--->Element

4. The chemical equation shown below represents a reaction that produces fuel for certain cars.CO + H2O------->CO2 + H2Which substance in this equation is classified as an element?

A CO B O2 C CO2 D H2

5. Which changes MUST happen for elements to become a compound?

A elements are heated B a gas becomes a liquid C elements dissolve in water D chemical bonds form between atoms.

6. Water (H2O), is not found on the periodic table because water is a...

A atom B liquid C mixture D compound

7. Which of the following explains why saltwater is considered a mixture?

A It is composed of one element. B It is composed of one compound. C It is composed of two or more substances and has new chemical properties. D It is composed of two or more substances and retains their own chemical properties.

8. Oxygen and iron combine chemically to form rust. Rust is classified as which of the following?

A an atom. B an element. C a compound. D a mixture.

9. When the elements copper (Cu) and oxygen (O) chemically combine, they form...

A an ion B a gas C a compound D a mixture

10. This image is a model of...

A an element B a compound C a homogenous mixture D a heterogeneous mixture