hypothesis, theories, and laws (unit: structures of the universe)

Which phrase is most likely to start a description of a scientific theory?

"Based on the observations made and experiments performed over the last fifty years . . ."

Which statement describes a scientific law?

A law is a proven fact that cannot be changed.

Which statement describes a scientific theory?

A theory changes based on new observations and testing.

Which statement is a scientific theory?

All matter is made up of particles, called atoms, that are constantly moving.

For which of these questions could a testable hypothesis be developed? Check all that apply.

Does the width of a rubber band affect how far it will stretch? How does the thickness of a material affect insulation? Do all objects fall to the ground at the same speed?

Chan Hee is inflating a basketball using an air pump. He notices that the pump gets warm as he uses it. What is a good hypothesis that could lead to new experimentation?

If air in a pump is squeezed more, then the air gets hotter because energy is added to it.

Yosef is playing with different kinds of rubber bands. Some are very narrow, and some are quite wide. Yosef is curious about the rubber bands and develops this scientific question: Does the width of a rubber band affect how easily it can be stretched? He decides to develop a hypothesis to test this scientific question. What could Yosef's hypothesis be?

If the width of a rubber band is increased, then it will be more difficult to stretch because more force will be needed to stretch it.

Doctors once believed that illness was caused by foul air and could not be transmitted from one person to another. Now, doctors know that single-celled bacteria and even smaller viruses cause illnesses and can be transmitted from one person to another. How did the advent of the microscope most likely affect the foul-air theory?

It allowed scientists to see small organisms in sick individuals and change the theory.

Nathan hypothesized that if the temperature of liquid water increased, the density would decrease because the volume would increase. He collected the data in the table below. How does Nathan's hypothesis lead to new investigations

The data do not support his hypothesis, so he should investigate why the density is greatest at 4°C.

Omar wrote a hypothesis about batteries called dry cells. If more dry cells are connected end to end, a light bulb will work longer because there is more energy available. What are the variables in his hypothesis?

The independent variable is the number of dry cells, and the dependent variable is the length of time the bulb works.

Ingrid wrote the hypothesis below. If the temperature of a liquid increases, the density of the liquid decreases because the particles move farther apart. What are the variables in her hypothesis?

The independent variable is the temperature, and the dependent variable is the density.

Based on early observations, including those in the table below, scientists proposed that the continents were once together but had drifted apart. However, scientists could not identify anything that would make them move. New technology, such as a worldwide network of earthquake detectors, led to new observations. Then scientists proposed that Earth's surface was divided into tectonic plates that would move as a result of forces linked to earthquakes and the formation of new ocean floor. How are continental drift and plate tectonics related?

The theory of continental drift was modified based on the new observations to become the theory of plate tectonics.

Explain why a law is accepted as fact, but a theory is not.

Theories are not accepted as fact because new information or technology can show that the theory is incomplete or incorrect. A law is accepted as fact because no exceptions have ever been found.

Explain why and how theories may be changed or replaced over time.

Theories may be changed over time as new information is discovered or new technologies are developed. New developments lead to changes in experimental methods, which provide information that may or may not support the existing theory. If the theory is still supported, it may be updated. If it is not supported, but the results are true and relevant, the theory may be replaced.

What effect, if any, does the development of new areas of science and technology have on theories?

Theories may change as a result of new information.

Initially, scientists described atoms as the smallest particles of matter. However, smaller particles within atoms were discovered. How did the scientific world respond to this new information?

by revising the theory that explained atoms to include this new information

Which statements describe a good hypothesis? Check all that apply.

can be tested, leads to a test with measurable results, provides a possible explanation to answer a scientific question

For which question could a testable hypothesis be developed?

does all wood float in water?

What is a main reason why the scientific model of atoms is considered a theory rather than a law?

it has been changed over time

A describes something in nature and predicts how it will behave without explaining why.

law

Every object that has mass attracts every other object with a gravitational force. It has been proven that the size of the gravitational force increases as the objects' masses increase but graviational force decreases rapidly as the distance between the objects increases.This statement about matter and its behavior is best classified as a

law

Use the drop-down menus to complete the statements. A is a factual statement about how something will behave. A is a well-tested explanation of a set of observations. A is a possible explanation of a scientific question that is testable.

law, theory, hypothesis

Identify the variables in this hypothesis. If an object's mass is increased, then the object's acceleration will decrease, because the object will be more resistant to change in motion. The independent variable is The dependent variable is

mass, acceleration

What happens when an experiment with new information or new technology produces results that support an existing theory?

the theory is revised or updated

The idea that the universe began from a single point and expanded to its current size explains a large number of observations, including those in the table below. In addition, many predictions based on the idea have led to additional observations that support it. This idea of the origin of the universe is best classified as a

theory

For which of these questions could a testable hypothesis be developed?

what makes a basketball bounce?

Under what condition will the results of an experiment based on a hypothesis most likely lead to new experimentation?

when the results do not match the experimenter's predictions

After an investigation, Kuri determines that her hypothesis was wrong. What is the best thing for Kuri to do next?

write a new hypothesis and conduct new experiments to explore the matter