Matter Matters
Air contains several different gases physically combined. How should air be classified?
Mixture
A substance has a definite volume but changes shape to fit its container. What state is it?
Liquid
Two surfaces rub against each other and motion becomes more difficult. What force is responsible?
Friction
A book is sitting on a high shelf. What type of energy does it have because of its position?
Potential energy
An atom has 15 protons. What is its atomic number?
15
Two different elements are chemically joined together in a fixed ratio. What type of substance has formed?
Compound
Water droplets appear on the outside of a cold glass. What change of state occurred?
Condensation
A rope is being pulled tightly from opposite ends. What type of force is acting on the rope?
Tension
The book falls from the shelf. What energy is increasing as it falls?
Kinetic energy
An atom contains 10 protons and 10 electrons. What is its overall charge?
Neutral
Ice melts into liquid water. Is this a physical or chemical change, and why?
Physical change; no new substance forms.
Dry ice changes directly from a solid into a gas. Name this change of state.
Sublimation
Rock layers are pushed toward each other and squeezed. What type of force are they experiencing?
Compression
A hot rock is placed into cold water. In which direction does heat transfer?
From the hot rock to the colder water
Where are protons and neutrons located in an atom, and where are electrons located?
Protons and neutrons are in the nucleus; electrons are outside the nucleus.
A student mixes salt into water until the salt seems to disappear. Another student burns a piece of paper. Which is a physical change and which is a chemical change? Explain.
Dissolving salt is physical because no new substance forms. Burning paper is chemical because new substances form.
A substance changes directly from a gas into a solid. Name the process. If it later changes directly back into a gas, name that process too.
Deposition, then sublimation.
Rock is being squeezed from two sides while another section of rock slides sideways past it. Identify the two types of forces occurring.
Compression and shear.
A ball is held above the ground and then dropped. Describe how its potential and kinetic energy change as it falls.
Potential energy decreases while kinetic energy increases.
An atom has an atomic number of 17. It gains 2 electrons. How many protons and electrons does it now have, and what is its overall charge?
17 protons, 19 electrons, and a −2 charge.
Substance A always contains the same elements chemically joined in a fixed ratio. Substance B contains several substances that can be physically separated. Classify A and B.
A is a compound/pure substance. B is a mixture.
Two identical objects have the same mass. One is taken to a place with much weaker gravity. Compare their mass, weight, and volume. Which measurement changes and why?
Mass and volume remain the same; weight changes because weight depends on gravity.
Two magnets attract each other from 2 cm apart. They are moved to 10 cm apart. What type of force is acting, and how will increasing the distance affect its strength?
Magnetic field force; it becomes weaker as distance increases.
A student pushes a 20-kg box with all their strength for 30 seconds, but it never moves. Did the student perform work on the box according to the scientific definition? Explain.
No. Work requires a force to move an object through a distance in the direction of the force.
An ion has 13 protons and a +3 charge. How many electrons does it have? Explain how you know.
10 electrons. It has 3 fewer electrons than protons, giving it a +3 charge.