STAAR Science Review

Which statements correctly compare metals and nonmetals?

• Metals tend to be good conductors of thermal energy. Nonmetals tend to be good insulators of thermal energy.

• Metals are dull and brittle. Nonmetals are shiny and malleable.

• Metals are good insulators of electricity. Nonmetals tend to be good conductors of electricity.

• Metals cannot be stretched into thin wires. Nonmetals can be stretched into thin wires.

Answer explanation

Statement F correctly highlights that metals are typically good conductors of heat and electricity, while nonmetals are not. This fundamental difference is key in comparing the two categories of elements.

Tags

NGSS.MS-PS3-3

What is the net force?

• 3 N

• 3 N, right

• 17 N, right

• 3 N, left

Answer explanation

The net force is the vector sum of all forces acting on an object. In this case, the net force is 3 N directed to the right, making '3 N, right' the correct choice.

Tags

NGSS.MS-PS2-2

A student is trying to classify an unidentified, solid gray material as a metal or a nonmetal. Which question will best help the student classify the material?

• F Is the material malleable or ductile?

• G Does the material feel hard to the touch?

• H Will the material float in water?

• J Does the material feel rough or smooth?

Answer explanation

To classify the material, the best question is whether it conducts electricity. Metals typically conduct electricity well, while nonmetals do not. Therefore, asking about electrical conductivity will help determine its classification.

Which pair of elements are nonmetals and gases at room temperature and normal atmospheric pressure?

• Boron, B

• Aluminum, Al

• Fluorine, F

• Cesium, Cs

• Chlorine, Cl

Answer explanation

Fluorine (F) and Chlorine (Cl) are both nonmetals and exist as gases at room temperature and normal atmospheric pressure, making them the correct choices. The other options are either metals or not gases.

One of the properties that makes copper, Cu, useful for household wiring is its ability to conduct electricity. Which other element is most likely to conduct electricity?

• Gold, Au

• Radon, Rn

• Bromine, Br

• Nitrogen, N

Answer explanation

Gold, Au, is a metal known for its excellent electrical conductivity, similar to copper. In contrast, radon, bromine, and nitrogen are non-metals and do not conduct electricity effectively, making gold the correct choice.

Tags

NGSS.MS-PS2-3

Based on this information, the element could NOT be a member of which group on the periodic table?

• Metals

• Metalloids

• Nonmetals

Which process describes only a physical change? (a)  

• Process 4

• Process 1

• Process 2

• Process 3

Answer explanation

Process 4 describes a physical change, as it involves alterations in form or appearance without changing the substance's chemical composition. The other processes may involve chemical changes.

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

• A rock breaks into smaller pieces when it is struck with a hammer.

• Rust forms on a hammer that has been left outside too long.

• A cup of water turns pink when a few drops of red food coloring are added.

• A solid is formed when heat is removed from a sample of water.

Answer explanation

Rust forming on a hammer indicates a chemical reaction, as it involves the transformation of iron into iron oxide due to oxidation. The other options describe physical changes or mixtures, not chemical reactions.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A student places a piece of potato into a container of hydrogen peroxide. One observation the student makes is that bubbles form around the potato. The presence of bubbles might indicate the formation of a new substance because bubbles -

• could show that a gas is forming

• always rise to the top of a liquid.

• are almost always perfectly spherical.

• usually burst after a few minutes.

Answer explanation

The formation of bubbles around the potato indicates that a gas is being produced, likely due to a reaction between the potato enzymes and hydrogen peroxide. Thus, the correct choice is that bubbles could show that a gas is forming.

Tags

NGSS.MS-PS1-2

Which of the following is an example that includes evidence of a chemical reaction?

• A sample of zinc is placed in water and it settles to the bottom.

• A solid block of ice is heated and it completely melts into a liquid.

• Sugar that is burned gives off an odor and turns brown and then black.

• A tomato is placed into a blender and chopped up into smaller pieces.

Answer explanation

The correct choice is the burning sugar example, as it shows a chemical reaction: the sugar changes color, gives off an odor, and produces new substances, indicating a transformation at the molecular level.

Tags

NGSS.MS-PS1-2