Density and the Periodic Table

• Inference involves conclusions or deductions based on observations.
• GRASS represents Given, Required, Application, Solution, and Statement.
• Precipitate refers to a chemical reaction where a solid forms out of a liquid.

Density

• Defined as Mass(g) divided by Volume(^3).
• Rounding is required.
• For unit conversions, if there are two of the same units, putting one units alone and multiply one on the denominator (obv. w the numerator)
• 1 cm^3 equals 1 mL.
• To calculate mass, multiply, and for density and volume, divide.
• Volume is calculated as D/M, Density as V/M, and Mass as VxD
• Density measures how much mass occupies a certain volume.
• Matter occupies space and has mass.
• Volume is the amount of space something occupies.
• All matter is made up of atoms.
• Atoms are made up of subatomic particles: protons, electrons, and neutrons.

Periodic Table

• Created by Dmitri Meldeeve.
• Arranged by increasing atomic number.
• Protons equal the atomic number.
• Electrons are negative atomic number.
• Neutrons are calculated by subtracting the atomic number from the mass number.
• Mass number is at the top and the atomic number is at the bottom in standard atomic notation.
• First 20 elements: H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca.
• Groups are arranged horizontally, comprising Alkali metals (first), Alkali earth metals (second), transition metals (3rd-12th), metalloids, halogens (17) and noble gases (18)
• To count atoms, multiply numbers in brackets then add when beside the element
• Molecules form when atoms chemically combine and exisit in air, molecules consist of Oxygen, Nitrogen, Water and carbon dioxide.
• Families/Groups: Vertical columns where elements share similar chemical properties.
• Energy shells are circles around the nucleus, with dots on the shells representing negative charge electrons and the nucles containing protons and neutrons
• When writing atomic notation, atomic number is at the bottom, atomic mass is at the top, and the atomic number is the same as protons and electrons.
• A heterogenous mixture contains easily distinguishable substances, like oil and water.
• Homogenous mixtures are uniform, making individual substances indistinguishable, like milk.
• A mixture involves two or more physically combined substances that are not chemically combined.
• A pure substance contains only one type of molecule or atom and cannot be separated.
• A solution is a mixture where everything is dissolved and appears uniform.
• A mechanical mixture is similar to a heterogenous mixture, with visible and separable parts
• Alloy: A mixture of two or more metals creating something stronger and useful.
• Suspension: A mixture with floating bits that settle over time.
• Elements cannot be broken down and contain only one type of atom.
• Compound: A substance made from two different atoms that are joined.
• Solute: What becomes dissolved.
• Solvent: What dissolves the solute, exemplified by sugar being the solute and water/milk as the solvent.

Physical and Chemical Properties

• Physical property: Measurable without changing the substance.
• Chemical property: How a substance reacts when new substances are forms.
• Physical change: Appearance changes, but the substance/chemical composition remain the same
• Chemical change: A substance reacts and forms a new substance with different properties as chemical composition alters and changes
• Physical changes are easily reversible, while chemical changes are not.

Unit Conversions

• Only move the decimals
• Kilo is the largest (1000), while milligram is the smallest (0.001).

Scientific Notation

• For numbers > 10, move the decimal point to the left (positive), right before the last digit
• For numbers < 1, move the decimal point to the right (negative), right before the last digit.
• "The cause" is the independent variable
• Independent variable: The one thing being changed in an experiment, usually by the experimenter, the x-axis on a graph
• "Result of an experiment" is the dependent variable
• Dependent variable refers to the result of the experiment, what is measured and what you changed as the y-axis on a graph.
• Controlled Group: A group in an experiment that remains constant throughout the entire experiment and serves as a comparison for the experimental group.
• Interpolation: Prediction or assumption of a value inside the time range
• Extrapolation: Prediction or assumption of a value outside of the time range
• Quantitative observations are measurable or countable data.
• Qualitative observations are descriptive, not numerical.