STAAR Category 1

Based on the information in the table, which conclusion about the chemical reactivity of these elements is valid?

• Boron is the most reactive because it has the most protons.

• Fluorine is the most reactive because it has 7 electrons in the outer shell.

• Silicon is the most reactive because it has an equal number of protons and neutrons.

• Gallium is the most reactive because it has many more neutrons than protons.

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

A student is studying the ways different elements are similar to one another. Diagrams of atoms from four different elements are shown below.

Which two atoms are of elements in the same group in the periodic table?

• Atom 1 and Atom 2

• Atom 1 and Atom 4

• Atom 2 and Atom 3

• Atom 3 and Atom 4

Which of these formulas contain equal numbers of nitrogen atoms?

• Formulas I and III

• Formulas I and IV

• Formulas II and III

• Formulas I, II, and V

Tags

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: All the reactants were liquids that evaporated.

  Procedure 2: A gas was formed as one product, and it escaped into the air.

• Procedure 1: One of the reactants was converted to thermal energy.

  Procedure 2: All the products were liquids.

• Procedure 1: The reactants were liquids with different densities.

  Procedure 2: The reactants were combined into only one product.

• 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.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A 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?

• 49.97

• 28.00

• 21.97

• 6.03

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

For an investigation a student poured a blue solution of CuSO₄ into a beaker. The student placed a shiny, silver-colored strip of zinc metal in the solution and observed the changes.

The student inferred that a chemical reaction occurred. What evidence supports this inference?

• A dark solid formed on the zinc metal.

• The zinc metal remained silver-colored and shiny.

• The CuSO₄ solution turned blue when the zinc metal was added.

• None of these

Tags

NGSS.MS-PS1-2

In the early 1900s many scientists thought that an atom consisted of a positive substance with negative charges scattered throughout the substance. Then Ernest Rutherford completed an experiment that changed the concept of the atom. His discovery led to the understanding that an atom consists mostly of empty space with -

• protons orbiting a dense nucleus made of electrons and neutrons

• electrons orbiting a dense nucleus made of protons and neutrons

• neutrons and protons orbiting a cloud of electrons

• electrons and protons orbiting a cloud of neutrons

Tags

NGSS.MS-PS1-1

What type of particles are found in the cloud surrounding the atom's nucleus?

• Positively charges particles and negatively charges particles

• Negatively charged particles only

• Neutral particles and positively charges particles

• Positively charges particles only

Tags

NGSS.MS-PS1-1

Which of the following best describes an electron?

• It has no charge and about the same mass as a proton.

• It has a negative charge and much less mass than a proton.

• It has a positive charge and much more mass than a neutron.

• It has a negative charge and about the same mass as a neutron.

Tags

NGSS.MS-PS2-3