Unit PS8.1-3 Test(half 9weeks)

• 1

• 2

• 3

• 4

Answer explanation

The formula C_{12}H_{22}O_{11} contains three different elements: Carbon (C), Hydrogen (H), and Oxygen (O). Therefore, the correct answer is 3.

Tags

NGSS.MS-PS1-1

What happens to the total mass of the substances after a chemical reaction?

• It decreases.

• It increases.

•  It remains the same.

• It increases then decreases.

Answer explanation

According to the law of conservation of mass, the total mass of substances remains the same before and after a chemical reaction. Therefore, the correct answer is that it remains the same.

Tags

NGSS.MS-PS1-5

What happens to the total mass of the substances after a chemical reaction?

• It decreases.

• It increases.

•  It remains the same.

• It increases then decreases.

Answer explanation

According to the law of conservation of mass, the total mass of substances remains the same before and after a chemical reaction. Therefore, the correct answer is that it remains the same.

Tags

NGSS.MS-PS1-5

• 1

• 2

• 3

• 4

Answer explanation

Baking soda's formula, NaHCO₃, contains 3 oxygen (O) atoms, as indicated by the subscript in the formula. Therefore, the correct answer is 3.

Tags

NGSS.MS-PS1-1

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products

• a total of 10g of products

• a total of 80 g of products

• a total of 20g of products

Answer explanation

According to the law of conservation of mass, the mass of reactants equals the mass of products. Starting with 20g of reactants, the reaction will produce a total of 20g of products.

Tags

NGSS.MS-PS1-5

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

Answer explanation

The Law of Conservation of mass states that mass is never created or destroyed in a chemical reaction. This means the total mass of reactants equals the total mass of products, making the correct choice 'Mass is never created or destroyed'.

Tags

NGSS.MS-PS1-5

Maria fills a bowl with 200 g of water. She puts the bowl of water in the freezer, and the water freezes. Which will most likely be the mass of the frozen water?

• 50 g

• 100 g

• 200 g

• 400 g

Answer explanation

The mass of the water remains the same when it freezes. Therefore, the mass of the frozen water will most likely be 200 g, as mass is conserved during the phase change from liquid to solid.

Tags

NGSS.MS-PS1-4

A chemical reaction is balanced when

• both sides have the same elements

• Both sides have the same  number of atoms

• Same subscripts

• Same coefficients

Answer explanation

A chemical reaction is balanced when both sides have the same number of atoms. This ensures that the law of conservation of mass is upheld, meaning the total mass of reactants equals the total mass of products.

Tags

NGSS.MS-PS1-5

What is a closed system?

• a system where none of the reactants or products are allowed to escape

• compounds made of thousands of repeating smaller molecules

• the output, or result of a chemical reaction

• occurs when the atoms and molecules of two or more substances rearrange to form new substances

Answer explanation

A closed system is defined as one where none of the reactants or products can escape, allowing for the conservation of mass during a chemical reaction. This distinguishes it from open systems where exchanges with the surroundings occur.

Tags

NGSS.MS-PS1-5

A boiling pot of water on a stove is what type of system

• Closed System

• Open System

Answer explanation

A boiling pot of water is an open system because it exchanges both matter and energy with its surroundings. Water vapor escapes into the air, demonstrating that matter is leaving the system.