Grade 8 Science Summative Assessment

A rock with a mass of 70 grams is dropped into a graduated cylinder with 30 mL of water in it. The water level rose as shown below.

Calculate the density of the rock in g/mL.

In which of the following examples has a chemical reaction occurred?

• After putting liquid batter into a hot pan, the batter solidifies and begins to turn brown.

• After turning on a blender filled with fruits, the fruit is chopped up and mixed together.

• After taking a tray filled with ice cubes out of the freezer, the cubes begin to melt.

• After adding a spoonful of sugar to a mug of hot coffee, the sugar dissolves completely.

In an experiment, two flasks of unknown, clear liquids are combined in a beaker and the following observations are obtained:

I. Solution color remains clear.

II. The amount of solution in the beaker increased.

III. Solution temperature changed from 10°C to 20°C.

IV. Some of the liquid remained in the flasks.

Which statements indicate a new substance was formed?

• III

• I

• II and III

• I and IV

Which of the following examples shows that a chemical change has occurred?

• Teeth chop up an apple slice into smaller pieces.

• Sugar placed in sugar water sinks to the bottom.

• A glass jar shatters into many pieces when dropped.

• Bleach gets rid of a ketchup stain on a white shirt.

During an investigation, a student combined the two clear, colorless solutions shown below.

The student observed that the temperature changed from 25° C to 23° C when the solutions were combined and that a white substance rapidly formed and settled to the bottom of the container.

What most likely happened to produce these results?

• One of the original compounds came out of the solution.

• The solutions reacted chemically.

• Some of the water froze into ice crystals.

• Rapid evaporation of water occurred, leaving a solid.

A chemical equation is shown.

4Si₂H₃ + 11O₂ → 8SiO₂ + 6H₂O

What is the total number of oxygen atoms on the right side of the arrow?

• 2 atoms

• 3 atoms

• 16 atoms

• 22 atoms

A chemical formula is shown below

C₆H₅OH

The subscripts in a chemical formula represent the

• number of atoms for the element present in the chemical formula

• atomic mass of the heaviest element in the compound

• atomic number of the element that follows the subscript

• column on the periodic table of the element next to it

Which of these compounds contains the same number of oxygen atoms?

Select TWO correct answers

• H₂O₂

• H₂SO₄

• HCIO₃

• H₂C₂O₄

• H₂O

A chemical formula is provided.

(NH₄)₂CO₃

How many atoms of hydrogen, H, are found in this substance?

• 2 atoms

• 4 atoms

• 6 atoms

• 8 atoms

A silver ring reacts with compounds containing sulfur in the air to form silver sulfide, a black substance that makes up the tarnish on the surface of silver objects. To remove the tarnish from the ring, students placed it in a pan lined with aluminum foil and added hot water. Baking soda was added to the hot water and stirred to create a solution. Students made observations about the process.

Which observation of this process provides evidence of a chemical reaction?

• Hot water heated the aluminum foil.

• The liquid solution changed color.

• The pan was lined with aluminum foil.

• The hot water slowly cooled over time.