Elements and Compounds

Which of the following is true of elements?

• All elements are naturally existing.

  
  

• An element is a pure substance that cannot be separated into simpler substances by physical or chemical means.

  
  

• Water is an element.

  
  

• Different sets of elements share similar physical properties, but they never share chemical properties.

  
  

How are elements in the periodic table organized?

• They are not organized in any particular pattern.

  
  

• They are organized alphabetically by their chemical symbols.

  
  

• They are organized into horizontal rows called periods and vertical columns called groups.

  
  

• They are organized into horizontal rows called groups and vertical columns called periods.

  
  

Which of the following is not a compound?

• water

  
  

• potassium iodide

  
  

• sodium chloride

  
  

• hydrogen

  
  

Which of the following is true of electrolysis?

• It separates water into one part hydrogen and one part oxygen.

  
  

• It causes the physical change of water into its component elements.

  
  

• It uses heat to break down a compound.

  
  

• It causes the chemical change of water into its component elements.

  
  

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Copper(I) chloride and copper(II) chloride are both formed by the combination of copper and chlorine. The different masses of copper that combine with a fixed mass of chlorine in the two different compounds can be expressed as a small whole-number ratio. This ratio supports which law?

• the law of conservation of mass

  
  

• the periodic law

  
  

• the law of multiple proportions

  
  

• the law of definite proportions