Part 2: STAAR GRADE 8 SCIENCE

The unusual strength of a glue makes it able to hold a heavy object, or load, as shown in the diagram below.

If the load exerts a strong downward force, the glue —

• A destroys the force

• B exerts a stronger downward force

• C causes the load to accelerate upward

• D exerts an upward force that is equal to the downward force

In November 2013 an object orbiting the sun seemed to disappear behind the sun. When a satellite did not detect the object, astronomers thought that the object had been destroyed when it passed close to the sun. However, when another satellite detected a small, bright object with a fan-shaped tail, astronomers proposed that the object was not destroyed.

What type of object were astronomers most likely observing?

• F A comet

• G An asteroid

• H A meteor

• J A nebula

A few years ago the population of male blue moon butterflies on the island of Samoa declined. One hypothesis for the decline of the male butterflies is that a parasite infected the cells of female butterflies. The parasite was passed to offspring through the females’ eggs and killed the male butterfly embryos. At one point during the decline, nearly all the butterflies in the population were females, but after five years the number of males in the population increased significantly.

Which explanation most likely accounts for the increase in the number of male butterflies in the five years after the initial parasite problem?

• A. Male butterflies in the population that survived were able to prey on the parasites living in the females’ egg cells.

• B.Female butterflies in the population that survived had a genetic adaptation that allowed them to transform into male butterflies.

• C. Male butterflies in the population that survived had a gene that made them resistant to the parasite, and they passed the gene on to their offspring.

• D. Female butterflies in the population that survived were able to protect the male eggs from the parasite and provide extra care for the male offspring.

Students in a science class made ball-and-stick models of the substances they were studying. The key shows the elements the students used in their models.

Which model represents an organic compound?

• 
• 
• 
• 

DDT is a pesticide that was once widely used to control agricultural pests and mosquitoes. However, this pesticide caused the eggshells of certain birds, including the brown pelican, to become fragile and thin. The adults would then accidentally crush the eggs while trying to incubate them.

What happened to brown pelican populations as a result of DDT use by humans?

• A. The populations increased much more slowly.

• B. The populations decreased as fewer eggs survived long enough to hatch.

• C. The populations remained stable over time.

• D. The populations increased as pelicans laid more eggs so that more offspring would survive.

The satellite image below shows a portion of the Namib Desert in Africa. This is an ancient, sandy desert with dunes that can be up to 305 m tall. The Namib Desert extends inland from the Atlantic Ocean between 80 km and 200 km and receives only 5 mm to 76 mm of rain each year.

A satellite picture of this same area taken weeks before shows that the shape and location of some sand dunes have changed. Which of these most likely caused the changes in the dunes?

• F Ocean waves

• G Flowing rivers

• H Blowing wind

• J Crustal uplift

A student listed how different parts of the body work to aid in the digestion of food.

Which of the following is a chemical change that occurs to the food?

• A The reduction in size of food particles as food is chewed

• B The movement of food to the stomach after food is swallowed

• C The breakdown of molecules of food by enzymes and acid in the stomach

• D None of the above

A meteor moving 468 km per minute traveling in a south-to-north direction passed near Earth in 2013. Because the meteor was only 45 m wide and was 27,700 km above Earth’s surface, it was not visible without the aid of a telescope.

Which statement describes the meteor’s motion?

• F Its velocity was 7.8 km/s northward.

• G Its acceleration was 468 km/s².

• H Its speed was 468 km/s northward.

• J Its acceleration was 7.8 km/s².

A chemist made the table below to record some atomic properties of four elements.

Based on the information in the table, which conclusion about the chemical reactivity of these elements is valid?

• A Boron is the most reactive because it has the most protons.

• B Fluorine is the most reactive because it has 7 electrons in the outer shell.

• C Silicon is the most reactive because it has an equal number of protons and neutrons.

• D Gallium is the most reactive because it has many more neutrons than protons.

Students in a science class in Marfa, Texas, made a poster with a diagram to represent a seasonal change in the Northern Hemisphere.

Which statement best describes conditions for Earth at Position 1 in the diagram?

• F There are an equal number of hours of daylight and nighttime in the Northern Hemisphere, and the North Pole is tilted away from the sun.

• G The Northern Hemisphere has the fewest hours of daylight, and Earth’s axis does not tilt at this position.

• H There are an equal number of hours of daylight and nighttime in the Northern Hemisphere because Earth’s axis is not tilted in this position.

• J The Northern Hemisphere has the fewest hours of daylight, and the North Pole is tilted away from the sun.