# Physical Science Study Guide (8th Grade)

Scientific Method
The scientific method is a way of solving problems. It involves the steps of asking a question, gathering information, forming a hypothesis, conducting an experiment, analyzing results, drawing conclusions, and communicating results.

How do scientists use the scientific method to solve problems?
Scientists use the scientific method to solve problems in a controlled manner, testing one variable at a time.

What are the two branches of physical science?
Physics and Chemistry

What is Matter?
Matter is anything with mass that takes up space.

What is SI?
SI refers to the International System of Units, or the metric system.

Why is SI important for all scientists to use?
Scientists around the world can use the metric system and easily communicate their ideas with one another, regardless of their native languages.

What are the SI units for length, mass, and volume?
Length is measured in meters; mass is measured in grams, and volume is measured in cubic meters (for a solid) or liters (for a liquid).

How do you find Density of an unknown soild?
To find the density of an unknown solid, you can measure its length, width, and height and multiply those together. That is the volume, and you can divide the mass by the volume to find the density. Another way is to drop the solid into a graduated cylinder with a known amount of liquid. The increase in mL is the volume of your solid. Then you can divide its mass by the volume. D = m/v

How do you find the density of an unkown liquid?
You use a granulated cylinder to find the liquids volume and triple beam balance to find its mass. Then divide the mass by the volume m/v

What are the differences between physical and chemical changes?
Physical changes occur without changing the identity of a substance. For instance, changing state (from solid to liquid to gas), changing color, changing size are all physical changes. Chemical changes, on the other hand, completely change the identity of a substance. For example, a chemical change involves iron reacting with oxygen to form rust.

What are the differences between phyisical properties and chemical properties?
Physical properties are traits that you can observe without changing the identity of a substance, like boiling point, color, malleability, or solubility. All of these can be observed without changing the molecular makeup of the substance. A chemical property can only be observed by changing the substance into something new; flammability can only be observed by setting something on fire, and reactivity can be observed by observing rust form. Chemical changes are not reversible, but physical changes are.

What are characteristic properties?
Characteristic properties are properties that do not change no matter how much of a substance you have. For instance, density, color, flammability, and reactivity are characteristic properties.

How do particles move in a solid versus a liquid and a gas?
In a solid, the bonds are very close together and the particles vibrate in place. In a liquid, because the bonds are a bit looser, the particles slide past each other. In a gas, the particles quickly move around and bounce off one another.

What happens to the bonds between particles as you the increase temperature?
As you increase temperature, you are giving substances more energy, which breaks/loosens bonds.Increasing temperature also causes the particles to move faster.

What is Boyles Law and how is it used in everyday life?
Boyle’s Law states that for a gas, pressure and volume are inversely related. For instance, when pressure increases, volume decreases, or vice versa, when pressure decreases, volume increases. As example would be stepping on a balloon.

What is Charles Law and how is it used in everyday life?
Charles’ Law states that for a gas, temperature and volume are proportionately related. This means that as temperature increases, so does volume, or as temperature decreases, the volume does as well. For example, cruise ships do not inflate their life rafts all the way because the increased temperatures will inflate the rafts more

How are melting point and bolining point alike and different?
Melting point is the point at which a substance will change from a solid to a liquid. It is the same as a substance’s freezing point (except with freezing, the substance is changing from a liquid to a solid). Boiling point also represents a change in state, but from a liquid to a gas (and it’s the same as condensation point, except condensation point is the point when something changes from a gas to a liquid).

What is a compound and give an example.
A compound is a substance made of two or more different elements chemically combined. For instance, sodium combines with chlorine to make sodium chloride, or table salt.

What is a solution, solute, and solvent?
A solution forms when particles from two or more substances are evenly mixed. Kool-Aid is an example, and with Kool-Aid, the water is the solvent (it does the dissolving) and the Kool-Aid powder is the solute (it gets dissolved).

What is a suspension?
A suspension is a mixture in which large particles of a material are more or less evenly dispersed throughout a liquid or gas. However, over time, the particles will settle out. Salad dressing made with oil and vinegar is a good example.

What is a collid?
A colloid is a substance that shares properties of both a solution and a suspension. Peanut butter, mayonnaise, and paint are colloids.

What is a mixture?
A mixture is a combination of several different substances, not chemically combined. Chex Mix is a mixture, as are all solutions, suspensions, and colloids.

What charge does a Proton have?
Positive

What charge does and electron have?
Negative

What charge does a Neutron have?
Neutral

What is an Atomic Number?
Atomic Number is the number of protons in an atom

How are ions and isotopes different?
Ions are charged particles, meaning they are atoms with unequal numbers of protons and electrons. Isotopes are variations of an element, having the same number of protons as all other isotopes of that element but different numbers of neutrons.

How are groups/families different from periods?
Groups/families are vertical columns on the periodic table. Families share characteristics. Periods are horizontal rows.

What are three characteristics of all metals?
All metals are ductile, meaning they can be stretched into wires. All metals are malleable, meaning they can be flattened into thin sheets. All metals conduct electricity. These qualities are possible because in metallic bonds, the electrons float around freely.

How are ionic bonds and covalent bonds different?
Ionic bonds occur between a positive metal and a negative nonmetal, and electrons are transferred from the metal to the nonmetal. Covalent bonds occur between two nonmetals, which share electrons.

How can you find the charge of an atom?
You subtract the number of electrons from the number of protons. For instance, an atom with 10 protons and 12 electrons has a -2 charge; 10 – 12 = -2.

What is the Law of Conservation Mass?
The law of conservation mass means that mass is neither created nor destroyed during chamicall equations

Diatomic Molecule
Diatomic molecules are molecules consisting of two atoms of the same type. Group 17, the halogens, forms diatomic molecules and so does oxygen. For instance, Cl2 and O2.

How are subscripts and coefficients different?
Subscripts are tiny numbers that tell you how many atoms you have in a molecule. If there is no subscript for an atom, you only have one atom of that type. Coefficients tell you how many molecules you have, and if there is no coefficient, it means you have one molecule.

How are acids and bases different?
Acids are bitter and create hydronium (H+) ions when put into water. Bases are bitter and they create hydroxide ions (OH-) when put into water.

What happens when acids and bases come into contact with one another?
Acids and bases will neutralize each other, creating water and a salt, when they come into contact with one another.