Physical Science Midterm Review

7th Grade Physical Science Midterm Review

Mass

The amount of matter in an object, measured in kilograms (kg) or grams (g)

Tool for measuring mass

Digital Balance or scale: an instrument used to measure the mass of an object

Prefix kilo

A prefix that means 1000, used in the metric system to denote multiples of the base unit

Prefix centi

A prefix that means 1/100, used in the metric system to denote fractions of the base unit

Prefix milli

A prefix that means 1/1000, used in the metric system to denote fractions of the base unit

Basic metric unit of length

Meter (m): the fundamental unit of length in the metric system

Best metric unit for measuring highway length

Kilometer (km): a unit of length equal to 1000 meters, commonly used for measuring long distances

Phase change from solid to liquid

Melting: the process by which a solid substance changes to a liquid state due to an increase in temperature

Phase change from liquid to solid

Freezing: the transformation of a liquid into a solid when its temperature is lowered

Phase with definite shape and volume

Solid: a state of matter characterized by a fixed shape and volume

Phase with neither definite shape nor volume

Gas: a state of matter that does not have a fixed shape or volume

Phase with water molecules having most energy

Gas: the state in which water molecules possess the highest amount of kinetic energy

Phase with water molecules having least energy

Solid: the state in which water molecules possess the lowest amount of kinetic energy

Density of water

1 gram per milliliter (g/mL): the mass of water per unit volume, commonly used as a reference for comparing the density of other substances

Object with density of 0.9g/mL in water

Float: an object with a density less than that of water, causing it to remain on the surface

Density of object that will float in water

Less than 1g/mL: the density required for an object to float in water

Freezing point of water

0°C: the temperature at which water changes from a liquid to a solid state

Boiling point of water

100°C: the temperature at which water changes from a liquid to a gaseous state

Educated guess

Hypothesis: a proposed explanation based on limited evidence, serving as a starting point for further investigation

Factor being tested in controlled experiment

Independent variable: the variable manipulated by the experimenter to observe its effect on the dependent variable

Pure water classification

Compound: a substance composed of two or more elements chemically combined in a fixed ratio

Chemical symbol for oxygen

O: the elemental symbol representing the chemical element oxygen

Chemical formula for carbon dioxide

CO2: the molecular formula representing the compound carbon dioxide, composed of one carbon atom and two oxygen atoms

Which is an element: oxygen or carbon dioxide

Oxygen: a chemical element located between oxygen and carbon dioxide on the periodic table

Formula to calculate density

Density = Mass/Volume: the mathematical expression used to determine the density of a substance based on its mass and volume

Density of 40g object with 10mL volume

Density = 4 g/mL: the density of an object calculated by dividing its mass by its volume

Reason for heated gas rising

Lower density than surrounding gas: the principle that warmer air or gas rises due to its lower density compared to the cooler surrounding air or gas

Reason for oil floating on water

Lower density than water: the phenomenon where oil floats on water due to its lower density

Building blocks of all matter

Atoms: the fundamental units of matter, consisting of protons, neutrons, and electrons

Electrical charge of a proton

+1: the positive charge carried by a proton, equal in magnitude to the negative charge of an electron

Electrical charge of a neutron

0: the neutral charge carried by a neutron, with no net electrical charge

Electrical charge of an electron

-1: the negative charge carried by an electron, equal in magnitude to the positive charge of a proton

Mass of a proton

1 atomic mass unit (amu): the standard unit of mass used for expressing the masses of atomic particles

Mass of a neutron

1 atomic mass unit (amu): the standard unit of mass used for expressing the masses of atomic particles

Mass of an electron

Nearly 0 amu: the extremely small mass of an electron compared to protons and neutrons

Particles in the nucleus

Protons and neutrons: the subatomic particles located within the nucleus of an atom

Center core of an atom

Nucleus: the central part of an atom, containing protons and neutrons

In a neutral atom, protons equal

Number of electrons: the number of protons in a neutral atom is equal to the number of electrons

Part of an atom involved in chemical bonding

Valence electrons: the electrons in the outermost energy level of an atom, responsible for forming chemical bonds

Location of metals on the periodic table

Left side: metals are predominantly located on the left side of the periodic table

Location of nonmetals on the periodic table

Right side: nonmetals are primarily located on the right side of the periodic table

Properties of metals

Malleable, ductile, good conductors: metals possess the properties of being able to be hammered into thin sheets (malleable), drawn into wires (ductile), and conducting heat and electricity

Greatest mass among proton, neutron, electron, nucleus

Nucleus: the central part of an atom, containing most of its mass due to the presence of protons and neutrons

Shorthand for representing a chemical reaction

Chemical formula: a concise representation of a chemical reaction using symbols and formulas for the reactants and products

Arrow in a chemical equation

Yields: the symbol used to indicate the direction of a chemical reaction, showing the transformation of reactants into products

Atomic number meaning

Number of protons: the atomic number of an element represents the number of protons in its nucleus

Protons in an atom with atomic number 10

10 protons: the number of positively charged particles in the nucleus of an atom with atomic number 10

Electrons in an atom with atomic number 10

10 electrons: the number of negatively charged particles orbiting the nucleus of an atom with atomic number 10

Electrons in the first energy level with atomic number 10

2 electrons: the maximum number of electrons that can occupy the first energy level of an atom

Electrons in the second energy level with atomic number 10

8 electrons: the maximum number of electrons that can occupy the second energy level of an atom

Protons in an atom with atomic number 3

3 protons: the number of positively charged particles in the nucleus of an atom with atomic number 3

Electrons in an atom with atomic number 3

3 electrons: the number of negatively charged particles orbiting the nucleus of an atom with atomic number 3

Neutrons in an atom with atomic number 3 and mass # 7

4 neutrons: the number of neutral particles in the nucleus of an atom, calculated by subtracting the atomic number from the mass number

Location of electrons in the atom

In energy levels or shells: electrons are arranged in specific energy levels or shells around the nucleus of an atom

Valence electrons location

Outermost energy level: valence electrons are found in the outermost energy level of an atom, determining its chemical properties

Valence electrons in group 2 elements

2 valence electrons: the number of electrons in the outermost energy level of elements in group 2 of the periodic table

Valence electrons in group 13 elements

3 valence electrons: the number of electrons in the outermost energy level of elements in group 13 of the periodic table

Elements in compound H2O

Hydrogen and Oxygen: the constituent elements of the compound water

Elements in compound NaHCO3

Sodium, Hydrogen, Carbon, Oxygen: 4 different elements (6 total atoms)

Ways to increase solution rate (dissolving)

Stirring, increasing temperature, crushing: methods to accelerate the dissolution of a solute in a solvent

Way to decrease rate of chemical reaction

Lowering temperature: reducing the temperature to slow down the speed of a chemical reaction

Base pH

Above 7: a pH value indicating the presence of a base or alkaline substance

Strongest base pH

Near 14: a pH value representing a highly alkaline or basic substance

Acid pH

Below 7: a pH value indicating the presence of an acidic substance

Strongest acid pH

Near 0: a pH value representing a highly acidic substance

Neutral substance pH

7: a pH value representing a neutral substance, neither acidic nor basic

Properties of acids

Sour taste, turn blue litmus paper red, react with metals: characteristic traits of acidic substances

Properties of bases

Bitter taste, turn red litmus paper blue, feel slippery: characteristic traits of basic or alkaline substances

Best for cleaning pots and pans

Bases: substances with alkaline properties are effective for cleaning kitchen utensils

Products of combining strong acid with strong base

Water and salt. Reaction called neutralization: the result of a chemical reaction between an acid and a base, forming water and a salt

Universal solvent

Water: a substance capable of dissolving a wide range of solutes, earning it the title of universal solvent

Separating sugar and water mixture

Evaporation: the process of separating a solute from a solvent by heating the mixture to evaporate the solvent, leaving the solute behind

Separating black sand and iron filings

Magnetic separation: a method of separating a mixture of magnetic and non-magnetic substances using a magnet

Determining remaining solid after evaporation

Taste or chemical testing: methods to identify and confirm the presence of a solid substance left behind after evaporation

Compound with one sodium, one hydrogen, one carbon, and 3 oxygen atoms

Sodium hydrogen carbonate, NaHCO3: a compound composed of sodium, hydrogen, carbon, and oxygen atoms in specific proportions

Examples of chemical change

Burning, rusting, cooking: processes that result in the formation of new substances with different properties

Amount of atoms on both sides of a chemical equation

Must be equal: the principle that the number of atoms of each element must be the same on both sides of a balanced chemical equation

Number of atoms in H2O

2 hydrogen, 1 oxygen: the composition of water, consisting of two hydrogen atoms and one oxygen atom

Number of atoms in H2SO4

2 hydrogen, 1 sulfur, 4 oxygen: the composition of sulfuric acid, consisting of two hydrogen atoms, one sulfur atom, and four oxygen atoms

Number of atoms in NaCl

1 sodium, 1 chlorine: the composition of sodium chloride, consisting of one sodium atom and one chlorine atom