atoms and matter
Which subatomic particle has a negative charge?
Electrons
What do scientists call the variable they deliberately change in an investigation?
The independent variable.
Water vapor cools and forms liquid droplets on a bathroom mirror. What phase change occurs?
Condensation. Water changes from a gas to a liquid.
What do we call the land area that drains into the same river, lake, or other body of water?
A watershed.
Water freezes in a rock crack and pushes it wider. Is this physical weathering, chemical weathering, or erosion?
Physical weathering. Expansion during freezing breaks rock without changing its mineral composition.
Which TWO formulas are compounds?
He CO2 N2 H2O
CO2 H2O
Students compare how light duration affects bean seedlings. They measure growth in centimeters. Identify the dependent variable.
The seedlings’ growth, measured in centimeters. This is the outcome the students measure.
A rounded water drop holds together. Water also clings to a paper towel. Name the property shown by EACH observation.
The rounded drop shows cohesion, attraction between water molecules. Clinging to the towel shows adhesion, attraction to another material.
Name the largest estuary in the contiguous United States. What two types of water mix in an estuary?
Chesapeake Bay. Fresh water and salt water mix in an estuary
Weak acid reacts with limestone and changes its minerals. Later, a stream carries the loosened particles away. Name BOTH processes.
The reaction is chemical weathering. The transport of loosened particles is erosion.
A neutral atom has 9 protons. How many electrons does it have? What does its atomic number equal?
9 electrons and atomic number 9. Neutral atoms have equal numbers of protons and electrons. Atomic number counts protons
A team compares seedlings receiving 4 or 8 hours of light each day. Name TWO conditions that should stay the same.
seedling species, starting size, water amount, soil, container size, temperature, or light intensity.
Table salt dissolves in water. Identify the solvent and solute. Does water dissolve every substance?
Water is the solvent. Salt is the solute. Water dissolves many substances, but it does not dissolve everything.
Classify each factor as biotic or abiotic.
Mayfly larvae Water temperature
Stream plants Dissolved oxygen
Biotic: mayfly larvae and stream plants. Abiotic: water temperature and dissolved oxygen.
After a storm, a creek looks cloudier. Which water-quality measurement probably increased? Does clearer water prove that it is safe to drink?
Turbidity probably increased. Clear water can still contain harmful dissolved substances or microorganisms. Appearance alone cannot establish safety.
In one molecule of NH3, how many nitrogen atoms and hydrogen atoms are present? What holds the atoms together, and which particles are involved?
1 nitrogen atom and 3 hydrogen atoms. Chemical bonds hold the atoms together. Bonding involves electrons.
A team tests each treatment once. Why would repeating each treatment several times improve the investigation?
Repeated trials help check consistency and reduce the influence of unusual results. Keep the controlled conditions the same in each trial.
A lake has a layer of floating ice. Why does the ice float? Explain what happens to water’s volume when it freezes.
Ice is less dense than liquid water. Water expands as it freezes, so the same mass occupies more volume.
A wetland lies beside a river that reaches an estuary. Explain one way the wetland helps water quality and one way the estuary helps young fish.
Wetlands can slow runoff and trap sediment or excess nutrients. Estuaries can provide sheltered habitat and food for young fish.
A fast stream carries muddy water farther downstream than a slow stream. Explain why, and name ONE action people can take to reduce sediment runoff.
Faster water has more energy to transport sediment and pollutants. Accept planting vegetation along banks, covering bare soil, or protecting wetlands.
A candle burns and produces carbon dioxide and water. Nearby, candle wax melts. Classify EACH change and explain the difference.
Burning is a chemical change because new substances form. Melting is a physical change because the wax changes state while remaining wax.
In a fictional experiment, 4 hours of light produces growth of 2 cm, 8 hours produces 5 cm, and 12 hours produces 7 cm. Give a conclusion supported by TWO values. Can the team predict growth at 24 hours with certainty?
Growth increased as light duration increased across the tested range: 2 cm at 4 hours and 7 cm at 12 hours. The team cannot be certain about 24 hours because it did not test that duration.
Two towns have similar latitude and elevation. One is beside a large lake. Explain why its temperatures can change less sharply. Also explain how water’s polarity helps molecules attract one another.
Water’s high specific heat lets it absorb or release much heat with a relatively small temperature change. Water molecules have partially positive and negative regions that attract opposite regions of nearby molecules.
List Virginia’s THREE major regional drainage destinations. Then explain how a divide and a tributary differ.
Chesapeake Bay, North Carolina sounds, and Gulf of Mexico (also accept Gulf of America). A divide separates drainage areas. A tributary is a stream that joins a larger stream or river.
Students spray equal amounts of water onto two equal-sized, equally sloped trays. One has bare soil and one has grass. They measure runoff volume. Identify the independent variable, dependent variable, and TWO controlled conditions. Name ONE limitation of the model.
Independent: surface cover. Dependent: runoff volume. Controls: water amount, tray size, slope, rain duration, soil type/amount, or collection time. Limitation: the tray cannot reproduce every real soil, landform, weather pattern, or watershed size.