Atoms, Elements, Compounds, Mixtures

Atoms are the smallest unit of an element and are composed of subatomic particles. An atom that has a balanced charge is referred to as “neutral”. Which of the following statements must be true about a neutral atom?

• The atom must have an even number of protons.

• The atom must have as many neutrons as protons.

• The number of electrons and protons in the atom must be equal.

• All of the neutrons and protons are found in the nucleus of an atom.

Nathan is examining the three models of atoms shown below. He knows that the models were developed in the following order: Thomson’s model, then Rutherford’s model, and finally, the current model based on modern atomic theory.

What can Nathan most likely conclude from these three related but different models?

• There are multiple ways to draw an atom, and all of them are correct.

• No one really knows anything about the structure of an atom.

• Scientists cannot seem to agree on the structure of an atom.

• Scientists build on and modify the work of other scientists.

Tags

NGSS.MS-PS1-1

The smallest piece of matter that still has the properties of an element is a(n) _________________.

• compound

• electron

• atom

• nucleus

What particle is NOT located in the nucleus?

• proton

• electron

• neutron

• quark

Look closely at part of the periodic table shown. Which of the following pairs of elements have properties that are the least similar?

• N and P

• Ge and Br

• He and Xe

• Cl and I

Steven noticed that one of the ingredients contained in his fruit-flavored snack was “artificial flavors.” One chemical used for that purpose is isopropyl acetate (CH₃COOC₃H₇). How many carbon atoms are present in one molecule of isopropyl acetate, CH₃COOC₃H₇?

• 1

• 2

• 5

• 6

Tags

NGSS.MS-PS1-1

Ethane, one of the smallest hydrocarbons, is used in the production of many other chemicals. How many hydrogen (H) atoms are shown in the model of ethane?

• 2

• 3

• 6

• 8

Tags

NGSS.MS-PS1-1

Francine’s mother made a fruit salad for breakfast. While Francine was eating her fruit salad, she exclaimed to her mother, ”I’m enjoying this mixture!”. Why did Francine refer to the fruit salad as a mixture?

• The fruit salad contains various ingredients mixed in fixed amounts.

• The fruit salad contains various ingredients that each retain their original chemical properties.

• The fruit salad contains components whose original chemical properties have been changed after mixing.

• The fruit salad contains various ingredients that can be separated only by using chemical means.

The illustration below shows the process of two different substances being combined. Which process does the illustration show?

• two pure substances physically combined to form a mixture

• two pure substances chemically combined to form a different pure substance

• a mixture separated into the components that were originally combined

• a solution formed by dissolving a solid in a liquid

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

In science class, Jonathan added a small amount of sand to a beaker of water. He stirred it vigorously so that all the sand swirled around in the water. Jonathan then claimed to his classmates that he had made a solution. However, his teacher told Jonathan that he was mistaken. Why was the teacher correct?

• Jonathan made a compound, not a mixture.

• A solid substance cannot dissolve in water to form a solution.

• The sand will eventually settle to the bottom and will not dissolve in the water.

• A chemical reaction did not take place, so a solution was not formed.