Chemistry STAAR Review

How many valence electrons are in an atom of each element in Group 15 in the periodic table?

A student drew atomic models of four elements.

Based on these drawings, which element is the least reactive?

• Neon, because it has two energy levels with eight electrons in the second level

• Chlorine, because it has three energy levels with seven electrons in the third level

• Gallium, because it has four energy levels with three electrons in the fourth level

• Tin, because it has five energy levels with four electrons in the fifth level

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NGSS.MS-PS1-1

Which statement accurately describes the atoms of a specific element?

• An indium‚ In‚ atom contains 115 protons inside the nucleus and 49 neutrons outside the nucleus.

• A scandium‚ Sc‚ atom contains 45 electrons outside the nucleus and 21 neutrons inside the nucleus.

• An aluminum‚ Al‚ atom contains 27 electrons and 27 protons inside the nucleus.

• A zinc‚ Zn‚ atom contains 30 protons inside the nucleus and 30 electrons outside the nucleus.

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NGSS.MS-PS1-1

Which chemical reaction involves the fewest oxygen atoms?

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NGSS.MS-PS1-1

As part of an investigation, students combined substances in a beaker to observe chemical reactions. They performed two procedures. They measured the mass of each substance before and after each reaction. The table shows their observations.

Assuming the students did not make any careless errors, what likely explains these changes in mass?

• Procedure 1: One of the products was a gas that escaped into the air. Procedure 2: A gas from the air reacted with one of the other reactants.

• Procedure 1: The reactants were liquids with different densities. Procedure 2: The reactants were combined into only one product.

• Procedure 1: One of the reactants was converted to thermal energy. Procedure 2: All the products were liquids.

• Procedure 1: All the reactants were liquids that evaporated. Procedure 2: A gas was formed as one product, and it escaped into the air.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Four students were asked to complete a table for a science assignment. Each student selected one chemical element from each of four groups in the periodic table and then classified each element as a metal, a nonmetal, or a metalloid. Which table was completed correctly?

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Both the esophagus and the small intestine are involved in the digestion of food. The esophagus squeezes food into the stomach by wave-like muscle contractions. Peptidase enzymes in the small intestine break food molecules into smaller molecules. Which statement best describes changes to food during digestion?

• The muscle contractions result in physical changes, while the action of the peptidase results in chemical changes.

• The muscle contractions and the action of the peptidase both result only in physical changes.

• The muscle contractions result in chemical changes, while the action of the peptidase results in physical changes.

• The muscle contractions and the action of the peptidase both result only in chemical changes.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which statement does NOT correctly compare silicon with another element?

• Silicon is a better conductor of electricity than sulfur.

• Silicon conducts electricity as well as copper does.

• Silicon is a solid at room temperature, but argon is a gas.

• Silicon is less malleable than silver.

Which statement correctly describes the location and charge of the electrons in an atom?

• The electrons are inside the nucleus and have no charge.

• The electrons are outside the nucleus and have no charge.

• The electrons are inside the nucleus and have a negative charge.

• The electrons are outside the nucleus and have a negative charge.

The table lists some compounds found in foods and their formulas.

Based on this information, which of these statements is NOT true?

• A molecule of sorbitol contains three more oxygen atoms than a molecule of glutamine does.

• A molecule of lactose contains twice as many atoms as a molecule of fructose does.

• A molecule of fructose contains four more atoms than a molecule of glutamine does.

• A molecule of lactose contains twice as many carbon atoms as a molecule of sorbitol does.

Tags

NGSS.MS-PS1-1