Science Units 1-4

matter

anything that has mass and takes up space

observation

using your senses to describe something you see, hear, smell, taste, or feel

inference

a conclusion or guess you make based on observations

accuracy

how close a measurement is to the true value

precision

how close repeated measurements are to each other

water displacement

a method to find the volume of an irregular object by seeing how much water rises when the object is placed in it

granular solids

small, grain-like solids (like sand or rice) that pour like a liquid but are still solid pieces

metric system

a universal measurement system based on powers of 10 (meters, liters, grams)

mass

the amount of matter in an object

volume

the amount of space an object or substance takes up

density

how much mass is packed into a certain volume (mass ÷ volume)

sigfig

the digits in a measurement that show how precise it is

reactivity

how easily a substance reacts with other substances

flammability

how easily something can catch on fire

malleability

the ability of a material to be bent or shaped without breaking

quantitative data

information that is measured or counted and written as numbers (like mass, temperature, length, or time)

qualitative data

information that is described using words and qualities, not numbers (like color, texture, smell, or appearance)

experimental errors

mistakes or uncertainties that happen during an experiment

independent variable

the variable you change on purpose in an experiment

dependent variable

the variable you measure or observe; it changes because of the independent variable

control group

the group that does not receive the experimental change; used for comparison

constants

factors that must stay the same in all trials of an experiment

physical properties

characteristics you can observe without changing the substance (color, mass, density, melting point)

chemical properties

Characteristics that describe how a substance reacts or changes into a new substance (flammability, reactivity)

properties of the objects

traits that describe what an object is like (shape, size, texture, mass)

percent error

a calculation that shows how far your answer is from the correct value

change in mass

the difference in mass before and after an experiment

physical changes

changes that affect appearance but do NOT create a new substance (cutting, melting, boiling)

chemical changes

changes where a new substance is formed (rusting, burning)

phase changes

changes of state: solid ↔ liquid ↔ gas

melting

solid → liquid

freezing

liquid → solid

boiling/evaporation

liquid → gas

condensation

gas → liquid

melting point/freezing point

the temperature at which a substance melts or freezes

boiling point/condensation point

the temperature at which a substance boils or condenses

heat

the transfer of thermal energy from something warm to something cooler

thermal energy

the total kinetic energy of the particles in a substance

kinetic energy

the energy of motion

temperature

the average kinetic energy of particles in a substance

Law of Conservation of Mass

mass is not created or destroyed; the amount of mass stays the same before and after changes

solution

a mixture where one substance is completely dissolved in another

solute

the substance that gets dissolved

solvent

the substance that does the dissolving

dissolving

when a solute breaks apart and spreads out evenly in a solvent

soluble

able to be dissolved

insoluble

not able to be dissolved

mixture

two or more substances physically combined

homogenous

a mixture that looks the same throughout; evenly mixed

heterogenous

a mixture where you can see the different parts

suspension

a mixture where particles are floating in a liquid but will settle over time

concentration

how much solute is dissolved in a solvent

dilute

a solution with very little solute (weak)

concentrated

a solution with a lot of solute (strong)

saturated

a solution that cannot dissolve any more solute at that temperature

precipitate

a solid that forms when two solutions react or when a solution becomes too full to hold more solute

unsaturated

a solution that can still dissolve more solute

solubility

the maximum amount of solute that can dissolve in a solvent at a certain temperature