Unit 2 Study Guide- Chem.

What makes particles move faster or slower?

Temperature. Higher temps = fast particles. Lower temps = slow particles

Exothermic reactions

Exothermic release heat, increase the temperature.

Endothermic reactions

Endothermic reactions absorb heat, decrease the temperature of surroundings

chemical change

Chemical fundamentally change what the substance is, irreversible, have to do with a chemical reaction.

physical changes

Physical changes are reversible (even if it’s just hypothetically), do not change what substance is.

Gas

no defined shape/volume

Liquid

defined volume, no defined shape

Solid

defined shape and volume

Aqueous

similar to or containing or dissolved in water/ essentially the same as liquid, but we use the term way more

heterogeneous mixture

Heterogenous are different throughout (not mixed well)

homogenous mixtures

Homogenous are mixed well and the same throughout. Homogenous mixtures include alloys and solutions!

Ionic

one metal and at least one nonmetal (like NaCl)

Covalent

two or more nonmetals (like CO3).

Organic

can be multiple elements, usually covalent, but always starts with C and H (like C6H12O6)

Numbers above Period Table mean?

atomic number, just another label or way of differentiating between elements

Numbers below Period Table mean?

atomic mass (how heavy the element is). If the mass is in parentheses, it means the element is radioactive, but it’s still the mass.

Alloy

homogenous, well-mixed, metals. Ex: sterling silver, which is silver + copper

Solution

homogenous, well-mixed, aqueous. Ex: apple cider vinegar, milk, vegetable oil

Decanting

pouring one layer of something off of another. Could be top layer from a pair of liquids or could be aqueous off of something settled on the bottom.

Sieving

separation based on size (usually two solids). Smaller pieces fall through, larger pieces stay in tray. Ex: large pieces of gold separated from pebbles

Distillation

separation based on boiling point, used to purify anything that has dissolved substances in it. Boils off part of it (usually water), leaves remaining impurities

Hand-picking

literally picking something out of a mixture by hand. Like if you wanted to separate your tea, the first thing to do would be to hand-pick the tea bag out.

Filtration

separation to remove something solid from an aqueous mixture. Solid part filters out, aqueous solution all goes through. Ex: filtering out coffee grounds from your morning coffee

Density equation

Density = mass/volume (units are g/mL or g/cm3)

Magnetic elements

Iron (Fe), Nickel (Ni), Cobalt (Co) - mostly we care about iron

Density of water

1.00 g/mL

Temperature conversion equations

Tk = Tc + 273
Tf = 1.8(Tc) + 32

Rf value equation

Rf = distance color traveled/distance solvent traveled ***pay attention to whether you have to subtract the starting line or not***

The difference between groups and periods on the PT?

Groups are columns - there are 18. They are often named (like halogens, alkali metals, etc.) Periods are rows - there are 7.

How to determine whether floats?

LESS dense than water.

How to determine whether sinks?

If MORE dense than water. Water’s density is 1.00 g/mL

How to read paper chromatography results?

Separates based on color. Ex: leaf color (green) breaks down into four different compounds. A marker’s black ink might be made of three or more different base colors. A solvent goes up the paper, dragging some parts of the color way up the paper and leaving some closer to the bottom. High up the paper = high Rf value. Low on the paper = lower Rf value.

Determine how to separate components of a mixture?

Need to be able to think through the processes listed below and when they are applicable or not. Ex: decanting won’t work if two layers are mixed together. Filtration won’t work if something is dissolved in water.