Formulas and Reactions REVIEW!

Formulas and Reactions REVIEW!

Super STAAR review!

8.5(D):

• Recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical formulas containing subscripts

• Subscripts tell how many atoms of an element there are. AKA H2 is 2 Hydrogens; H2O is 2 Hydrogens and 1 Oxygen.

8.5(D):

• Coefficients out front tell how many molecules there are.

• You must multiply every atom type in a molecule by this number (distribute!)

8.5(D):

• Parentheses indicate repeated segments with multiple elements.

• Multiply each element type inside parentheses by number outside.

Multiple Choice

A compound secreted by honeybees to paralyze intruders in their hive is known as 2-heptanone. The formula for this compound is shown.

How many atoms of each element are in one molecule of 2-heptanone?

• 4 carbon atoms, 11 hydrogen atoms, and 1 oxygen atom

• 7 carbon atoms, 14 hydrogen atoms, and 1 oxygen atom

• 7 carbon atoms, 11 hydrogen atoms, and 8 oxygen atoms

• 6 carbon atoms, 14 hydrogen atoms, and 3 oxygen atoms

Fill in the Blank

Barium sulfate, BaSO4 , is a white crystalline solid that is insoluble in water. It is used by doctors to diagnose problems with the digestive system. Barium hydroxide, Ba(OH)2 , is also a white crystalline solid and is used in wastewater treatment. How many more oxygen atoms are represented in the formula for barium sulfate than in the formula for barium hydroxide? Type your number answer below:

Multiple Choice

Which chemical reaction involves the fewest oxygen atoms?

8.5(E)

• Investigate how evidence of chemical reactions indicates that new substances with different properties are formed and how that relates to the law of conservation of mass.

• City Girls Love Their Cell Phones On!

• Create new substance, Gas, Light, Temperature change, Color change, Precipitate, Odor!

Multiple Choice

Which statement best describes evidence that a chemical reaction occurs as a cake bakes?

• The water in the cake batter evaporates.

• The cake rises as gas bubbles form in the baking cake.

• The cake takes the shape of the container in which it is baked.

• The water in the cake batter is used to keep the cake moist as it bakes.

Multiple Choice

For a laboratory investigation some students put a strip of shiny metal into a beaker of blue solution and then stored the beaker on a shelf overnight. The next morning, the students recorded observations about the metal and the solution in the image.

Based on their observations, can the students correctly conclude that a chemical reaction occurred?

• No, because the metal strip was still visible

• Yes, because a new material of a different color formed on part of the metal strip

• No, because the solution stayed blue

• Yes, because the volume of the blue solution stayed the same

7.6(A)

• Distinguish between physical and chemical changes in matter

• Physical change: Chemical formula stays the same

• Chemical Change: Chemical formula is altered

Multiple Choice

Researchers are investigating processes that happen during digestion. Which answer choice describes only a physical change during digestion?

• Hydrochloric acid in the stomach breaks down proteins.

• Chewing in the mouth breaks food into small pieces.

• Enzymes in saliva start the digestion of starches before food is swallowed.

• Bacteria in the intestines convert dietary fiber into fats.

Multiple Choice

Both the esophagus and the small intestine are involved in the digestion of food. The esophagus squeezes food into the stomach by wave-like muscle contractions. Peptidase enzymes in the small intestine break food molecules into smaller molecules.

Which statement best describes changes to food during digestion?

• The muscle contractions result in physical changes, while the action of the peptidase results in chemical changes.

• The muscle contractions and the action of the peptidase both result only in physical changes.

• The muscle contractions result in chemical changes, while the action of the peptidase results in physical changes.

• The muscle contractions and the action of the peptidase both result only in chemical changes.

6.6(B)

• The student is expected to calculate the density to identify an unknown substance.

• Density = mass/volume

Multiple Choice

The mass of an unidentified rock is 15.5 grams. Students determine the volume of the rock by placing the rock in a cylinder with water. The students calculate the density of the rock. They determine the identity of the rock based on the density ranges in the table.

The students most likely have which type of rock?

• Coal

• Dolomite

• Peridotite

• Sandstone