ACOS 2 - Pure Substances

Filtration, or screening, is one way to separate certain mixtures, as shown in the image. Which of these mixtures could be most easily separated by filtration?

• oil and water

• dissolved sugar and water

• sugar and salt

  
  

• flour and marbles

  
  

Your teacher has given each lab group four liquids. Each liquid has been tinted using food coloring. Your teacher has asked you to pour all four liquids together and then devise a method to separate the four back into their individual containers. This  is an illustration of your lab partner pouring the four liquids into a beaker. "This will be easy to do!" both you and your partner exclaim. Explain why it will be easy to separate the four liquids.

• The liquids will not mix, but rather separate, because they all have a unique density.

  
  

• The liquids will not mix, but rather separate, because they all have a different weight.

  
  

• The four liquids have a different boiling point so you can heat the mixture and each liquid will boil off at a different temperature.

  
  

• The four liquids separate into four layers because you have poured them into the beaker: oil, water, oil, water. We know that oil and water do not mix.

  
  

Tags

NGSS.MS-PS1-2

Tim is given a powdered sample of a mixture of lead nitrate and silica sand. When this mixture was added to water, he notices that the amount of powder decreases. So Tim has used ___________ to separate the components of the mixture.

• density

• melting point

  
  

• solubility

• temperature

A hypothetical situation of being stranded on a deserted island without water is often posed to students. A model of a process used to separate salt water into its components is shown here. Justify the use of the flame in the model depicting the separation of the mixture.

• The flame will sterilize the water, so that water from the ocean will be consumable. This is known as sanitation.

• The flame will allow the pure water and salt water to separate into different layers. This is known as density separation.

  
  

• The flame will burn the salt component of the mixture, leaving only the pure water behind for drinking. This is known as combustion.

  
  

• The flame will allow the water to evaporate and be collected in its pure form, leaving the salt component behind. This is known as distillation.

  
  

Matter may be classified as a pure substance or a mixture. Where on the Venn diagram would you insert the term "pure substance"?

• A

• B

• C

• D

You are presented with four chemical compounds. Each compound contains a different metal. When the compound is heated in a flame a distinct color is emitted as the electrons are excited and give off different wavelengths of light. Determine the unknown compound based on the data table and photo.

• barium chloride

• calcium chloride

• copper (II) sulphate

• potassium nitrate

Tags

NGSS.MS-PS1-2

Josh is designing a lab to separate a mixture of SULFUR POWDER and IRON FILINGS. He looks at all the ways to separate a mixture but decides that one way would work the best on this mixture. What method should Josh use?

• density

•  filtration

• evaporation

• magnetic attraction

Josh is designing a lab to separate a mixture of SALT and WATER. He looks at all the ways to separate a mixture but decides that one way would work the best on this solution. What method should Josh use?

• density

•  filtration

• evaporation

• magnetic attraction

  
  

You have been given a mixture of water and a unknown solid substance. Your teacher asks you to perform a heating process to determine what the unknown substance is. When the temperature reaches 100 °C, the water begins to boil and you are left with a white crystalline substance. When your thermometer reaches 200 °C, everything in the container becomes a liquid. You can conclude that the unknown substance is

• lead

• aluminum

• table salt

• table sugar

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

Salt is added to water. You speed up dissolving by stirring the salt into the water. Then your teacher challenges you to separate the salt from the water. You know that the salt and water have formed a solution and that the salt is distributed throughout the glass of water.

What would be the BEST way to separate the salt and the water?

• Collect the salt as it floats in the water.

• Heat the solution to boiling and evaporate off the water.

• Spin the solution at a high speed to separate out the salt.

• Pour the solution through filter paper to filter out the salt.