Elements, Compound & Mixture

Which of the following is an example of the formation of a mixture?

• Rust forming on an iron nail.

• Sugar crystals dissolving in water.

• Sodium and chlorine forming table salt.

• Hydrogen and oxygen reacting to produce oxygen.

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

• Oxygen is more reactive than air.

• Oxygen has a higher density than air.

• Oxygen goes under a phase change, whereas air is always a gas.

• Oxygen contains only one substance, but air contains several substances.

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

• A tire filled with air.

• A jar filled with salt water.

• A balloon filled with helium.

• A glass filled with chocolate milk.

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

• Water-->Compound 

  Hydrogen-->Compound

   

  Oxygen--->Element

• Water-->Compound

   

  Hydrogen--->Element

   

  Oxygen--->Compound

• Water--->Compound

   

  Hydrogen--->Element

   

  Oxygen--->Element

The chemical equation shown below represents a reaction that produces fuel for certain cars.

CO + H₂O------->CO₂ + H₂

 

Which substance in this equation is classified as an element?

• CO

• O₂

• CO₂

• H₂

Which changes MUST happen for elements to become a compound?

• chemical bonds form between atoms.

• elements dissolve in water

• a gas becomes a liquid

• elements are heated

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

• atom

• compound

• liquid

• mixture

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

• It is composed of one element.

•  

  It is composed of one compound.

• It is composed of two or more substances and has new chemical properties.

• It is composed of two or more substances and retains their own chemical properties.

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

• an atom.

• an element.

• a compound.

• a mixture.

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

• an ion

• a gas

• a compound

• a mixture