Staar High School Chemistry Review

Some students are using samples of different substances for a lab investigation. They plan to observe the physical properties of each substance and record their observations in a table like the one below. Which of the substances observed are elements?

• S, Fe, O, Sr, and Al

• S, O, and LiF

• NO, O,and LiF

• NO,Fe,Sr,and Al

Tags

NGSS.MS-PS1-1

Element R and Element Q have the same number of valence electrons. These elements both have similar chemical behavior, but Element R has fewer energy levels than Element Q. Which statement best describes the positions of the two elements in the periodic table?

• The two elements are in the same period, with Element R the first element in the period and Element Q the last element.

• The two elements are side by side in the same period, with Element Q to the left of Element R.

• The two elements are in the same group, with Element R just above Element Q.

• The two elements are in the same group, with Element Q at the top of the group and Element R at the bottom.

Tags

NGSS.MS-PS1-1

A student obtains two strips of magnesium, Mg, ribbon that are each 3 cm long. One strip of magnesium is placed in a test tube containing 5 mL of water, and the other strip is placed in a test tube containing 5 mL of hydrochloric acid, HCl. Both liquids are at room temperature. The student’s observations are recorded in the table. Which statement is not supported by the student’s observations?

• A chemical reaction takes place between magnesium and hydrochloric acid.

• A gas is released in Test Tube 2.

• The substances in both test tubes are reactive only at high temperatures.

• Energy is released in the reaction involving hydrochloric acid.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

NGSS.MS-PS1-5

What is the difference between the number of electrons in an atom of selenium, Se, and the number of electrons in an atom of aluminum, Al?

• 21

• 3

• 51.989

• 105.953

Four students were given a list of compounds and asked to identify which ones are organic. Which student correctly identified the organic compounds in the list?

• Student K

• Student L

• Student M

• Student N

Tags

NGSS.HS-LS2-5

Four students were asked to name the parts of an atom that determine the atom’s identity and chemical properties. The students’ responses are shown in the table below. Which student’s responses are correct?

• Student 1

• Student 2

• Student 3

• Student 4

Tags

NGSS.MS-PS1-1

Strontium phosphate, Sr₃(PO₄)₂ is a crystalline substance used in medicine and industry. How 42 many phosphorus atoms are represented in the formula for

Sr₃(PO₄)₂?

?

• 2

• 3

• 4

• 8

Tags

NGSS.MS-PS1-1

chemical reaction in which calcium carbonate, CaCO₃, is decomposed results in the production of two simpler compounds. What mass of calcium carbonate, to the nearest hundredth of a gram, is decomposed in this reaction?

• 21.97g

• 28.00g

• 49.97g

• 6.03g

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Students in a science class prepared flashcards so that they could quiz one another about the arrangement of the periodic table. One of the flashcards contained information about two elements, Element L and Element M. The students had to use the information on the flashcard to determine possible positions of the two elements on a blank periodic table. Which periodic table has the elements placed in locations that match the information on the flashcard?

• 
• 
• 
• 

Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural sources, such as forest fires, lightning, and microbial activity in soil. The equation for producing nitrogen dioxide is shown below. Which of these provides evidence that a chemical reaction occurs?

• A gas is present.

• The total number of atoms remains unchanged.

• The state of matter remains the same.

• A brown gas is produced.

Tags

NGSS.MS-PS1-2