Chemistry Review

Students react baking soda & vinegar.
Which of the following would provide the evidence that the number of atoms present before a chemical reaction is equal to the number of atoms present after the chemical reaction?

• The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.
• Bubbles were produced during the reaction, which meant that a gas was being produced.
• The plastic bag did not change in any way, indicating that it was not involved in the reaction.
• The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

Tags

NGSS.MS-PS1-5

Suppose a reaction were to happen in an open container in a lab. During the reaction, the scientist observes the chemicals bubble, and produce a gas. During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g. Explain what happened.

• His chemical reaction defied the law of conservation of mass

• The product destroyed mass during the reaction

• The reactants created matter during the reaction

• The gas that was produced was not able to be weighed since the container was open.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

A chemical reaction is balanced when

• both sides have the same elements
• Both sides have the same  number of atoms
• Same subscripts
• Same coefficients

Tags

NGSS.MS-PS1-5

How many oxygen atoms are in this chemical formula?

• 6 oxygen atoms

• 2 oxygen atoms

• 3 oxygen atoms

• 4 oxygen atoms

Tags

NGSS.MS-PS1-1

In a reaction A + B ----> C,  reactant A has 5g and product  C has 9g. How many grams does reactant B should have? 

• 4g
• 5g
• 9g
• 14g

Tags

NGSS.MS-PS1-5

Endothermic reactions...

• release energy
• explode
• take in energy
• have higher energy in their reactants than the products

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NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS1-6

Exothermic reactions

• have higher energy in their products than their reactants
• release energy
• get cold
• are synthesis reactions

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NGSS.MS-PS1-4

NGSS.MS-PS3-4

Molecule

• A group of atoms bonded together
• Basic unit of a chemical element
• Coefficient
• Subscript

Tags

NGSS.MS-PS1-1

Balance this equation.
_CF₄ + _Br₂ -- _CBr₄ + _F₂

• 2,1,2,1
• 1,2,2,1
• 1,2,1,2
• 2,2,2,2

Tags

NGSS.MS-PS1-5