Chemical Reactions Review

Draw a model of this chemical equation:

2CO₂ + H₂O −> H₂CO₃

Label the reactants and label the products

Draw a chart to identify the elements in both and the number of atoms of each on the reactant and product sides.

Answer explanation

The reactants are H₂O and CO₂, containing 2 atoms of hydrogen, 1 atom of carbon, and 3 atoms of oxygen. The product, H₂CO₃, contains the same elements and number of atoms. This is an example of the Law of Conservation of Mass because the same elements and number of atoms are balanced in the reactants and the products; no mass/matter was created or destroyed, the atoms were just rearranged by formation of new bonds.

Tags

PS1.A and PS1.B

A reaction produces 3 molecules of the same compound. Examine the model and draw the products. Label the reactants and the products, adding + signs and an arrow.

Answer explanation

Arrangement of reactants to the left of the arrow can vary, as long as it is different from the product (shown to the right of the arrow) and includes all atoms. Because it was given that there are 3 molecules of the same compound, we know that each one contains 1 of substance 2 and 2 of substance 1.

Tags

PS1.B

Look closely at the water molecules shown to the left. Heat was added increasingly going from the solid state to the gas state. Write a claim, give evidence, and support with reasoning as to whether or not a chemical change occured.

Answer explanation

No chemical reaction occurred here. The molecules are all H₂O and no bonds were broken or formed in changing the states of matter from solid to liquid to gas.

Tags

PS1.A

The chemical reaction for photosynthesis, without the coefficients for the reactants, is shown here:

___CO₂ + ___ H₂O (+ light) → C​₆H₁₂O₆ + 6 O₂

What is the missing coefficient for both CO₂ and H₂O?

Answer explanation

The complete chemical equation for photosynthesis is

6CO₂ + 6H₂O (+ light) --> C6H₁₂O₆ + 6O₂. With the products given, there are 6 carbon atoms, (6C...), 12 hydrogen atoms (6H₂) and 18 oxygen atoms (O₆ and 6O_2, which equals 18 when added together. The only way to get this without changing the substances is to include a coefficient of 6 for both CO₂ and H₂O in the reactants.

Tags

PS1.B

For this chemical reaction, what are the REACTANTS?

6CO₂ + 6H₂O (+energy) --> C6H₁₂O₆ + 6O₂

• C6H₁₂O₆

• 6H₂O

• 6O₂

• 6CO₂

Tags

PS1.B

For this chemical reaction, what are the PRODUCTS?

6CO₂ + 6H₂O (+ light energy) --> C6H₁₂O₆ + 6O₂

• 6CO₂

• 6O₂

• 6H₂O

• C₆H₁₂O₆

Tags

PS1.B

What is an element?

• A material made by chemically altering natural materials

• A pure substance consisting of one type of atom

• The smallest unit of matter

• Formed when two or more atoms bond together

Tags

PS1.A

This is a picture of a(n)

• Atom

• Molecule

• Element

• Compound

Tags

PS1.A

A chemical reaction is:

• When the atoms in a substance rearrange to form a new substance

• Formed when two or more atoms bond together

• A pure substance consisting of one type of atom

• A material made by chemically altering natural materials

Tags

PS1.B

A physical reaction/physical change is:

• When the atoms in a substance rearrange to form a new substance

• Formed when two or more atoms bond together

• When a substance is changed but the atoms are NOT rearranged.

• A material made by chemically altering natural materials

Tags

PS1.B