Ms. Lawson needs help figuring out which models are pure substances. Which of the following models represents pure substances with the correct explanation?

• Picture III because the compounds can be chemically separated.

• Picture II and III because they both contain only one type of compound.

• Picture III because they can be physically separated.

• Picture I and II because they only consist of one element or one compound.

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NGSS.MS-PS1-1

A molecule is defined as two or more atoms chemically bonded together. A compound is defined as two or more different types of atoms bonded together, which of the following statements is true about compounds and molecules?

• Compounds are not pure substances.

• All molecules are compounds.

• All compounds are molecules.

• Molecules are mixtures.

If compounds are two different elements chemically bonded together, which of the following is considered a compound?

• 
• Ne (Neon)

• Water

• Oxygen

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NGSS.MS-PS1-1

Remember, compounds have chemical formulas which tell us how many atoms are in the compound. How many total atoms are in the compound to the left?

• 4

• 5

• 6

• 7

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NGSS.MS-PS1-1

Pure substances such as elements and compounds can be physically separated.

• True

• False

Select all of the following substances which would be considered homogeneous mixtures:

• Carbon Dioxide

• Air

• Water

• Soda

True or false? When substances are physically combined in a mixture, the physical properties of each component do not remain the same.

• True

• False

Answer explanation

Which of the following is true about mixtures?

• Mixtures are chemically combined and have to have a set ratio of each substance.

• Mixtures are physically combined and do not have a set ratio of each substance.

• Mixtures cannot be physically separated because they are chemically combined.

• Mixtures are physically combined but can only be chemically separated.

What is the difference between pure substances and mixtures?

• Both of them are physically combined.

• Pure substances can be physically separated while mixtures can be chemically separated.

• Both of them are chemically combined.

• Pure substances are chemically bonded while mixtures can be physically separated.

Which of the following is a pure substance?

• Orange juice because there is a set ratio of elements chemically bonded together.

• Air because there is a set ratio of elements physically mixed together.

• Salt water because there is a set ratio of elements that can be physically separated.

• Carbon dioxide because there is a set ratio of elements chemically bonded together.

Tags

NGSS.MS-PS1-1