Middle School Chemistry

What will weigh more when a chemical change is complete?  The reactants before the chemical reaction, or the product after the reaction is complete?

• They both will weigh the same
• The product always weighs more than the reactant
• The reactant will weigh more than the product
• They both will loose mass after the reaction

Tags

NGSS.HS-PS1-7

What is the Law of Conservation of mass?

• Mass is created in a chemical reaction
• Mass is created in a physical change
• New chemicals formed from a chemical reaction have a larger overall mass than the original reactants
• Mass is never created or destroyed

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-7

Which are the reactants in the following reaction?
2Mg + O₂ ---> 2MgO 

• Mg and O
• MgO
• Mg and MgO
• O and MgO

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-5

In oxides of nitrogen, such as N₂O, NO, NO₂, and N₂O₃, atoms combine in small whole-number ratios. This  evidence supports the law of

• definite proportions
• gravity
• multiple proportions
• conservation of mass

According to the law of definite proportions, any two samples of KCl have

• same melting point
• same mass
• same ratio of elements
• different structures

Isotopes are atoms of the same element that have different

• masses
• # of protons
• # of electrons
• chemical properties

All atoms of the same element have the same

• atomic mass
• mass number
• number of neutrons
• atomic number

An aluminum isotope consists of 13 protons, 13 electrons, and 14 neutrons. Its mass number is

• 13
• 14
• 27
• 40

Tags

NGSS.MS-PS1-1

The atomic number of neon is 10. The atomic number of calcium is 20. Compared with a mole of neon, a mole of calcium contains

• 2x atoms
• 1/2 x atoms
• same # atoms
• no answer is correct

2 moles = ? atoms

• 1.204 x 10²⁴
• 6.022 x 10²³
• 3.011 x 10²³