Chemistry - Chapter 1 Matter and Change

Explain density lab

Explain density lab

Place an object in a certain amount of water and measure the water displacement in mL. The amount of water displaced by the object is the volume.

Weigh the object in grams using an electronic balance. This is the mass of the object.

Density is equal to mass over volume, so divide the mass by the volume to get the density in g/mL.

Explain paper chromatography lab

On a piece of paper, draw a line with pencil about 1 cm from the bottom. On this line, place the samples that you want to observe on this line. Then, place the piece of paper in a water level that is below the 1 cm line. Watch as the chemicals are separated. The polar chemicals will be hydrophilic, meaning that they will be attracted to water, causing them to spread farther than the nonpolar chemicals which are hydrophobic. The hydrophobic chemicals will stay closer to the 1 cm line.

What is the purpose of paper chromatography?

to separate chemicals

Matter

anything that has mass and takes up space

Mass

the measure of the amount of matter (does not change)

Weight

the measure of the effect of gravity on matter (can change)

Mass vs. Weight

Mass does not change. It is the measure of the amount of anything that takes up space.

Weight can change based on how gravity affects things with mass (matter)

Atom

the smallest part of an element with all the properties of that element

Molecule

Two or more different types of atoms chemically bonded

Element

a pure substance made up of only one type of atom

Compound

a pure substance made up of only one type of molecule

Pure substances

simplest form, cannot be broken down physically

1. Elements - atoms

2. Compounds - molecules

Mixtures

can be separated physically

1. Homogeneous – is uniform throughout (solutions)

2. Heterogeneous – has distinct parts in a mixture

Homogeneous

is uniform throughout (solutions)

Heterogeneous

has distinct parts in a mixture

What are elements made up of?

one type of atom

What are compounds made up of?

one type of molecule

Explain separation of a mixture by distillation

A distilling flask is placed above a bunsen burner with a mixture, for example. alcohol and water. In this flask is a thermometer. Heat the flask with the bunsen burner until you reach the boiling point of alcohol. Once the alcohol evaporates, the vapors go through a tube called a condenser. A condenser is a tube surrounded by cold water, causing the alcohol vapors to condense back into alcohol droplets. The alcohol droplets will fall into a receiving flask, leaving you with only water in the distilling flask and only alcohol in the receiving flask.

2 ways to separate a mixture physically

Paper chromatography, distillation

1 way to separate a mixture chemically

Electrolysis

How does electrolysis work?

Compounds can only be separated by chemical means into its elements.

Ex: with the application of electricity, water can be separated into its elements.

2H^2O --→ 2H^2 + O^2

Extensive properties

depend on how much matter is present

Ex: mass, volume, length, energy

Intensive properties

do not depend on how much matter is present

Ex: density, color, melting point & boiling point, conductivity

Physical properties

characteristics of matter that can be observed without changing the substance

Ex: color, melting point, boiling point, freezing point, change of state, malleability, conductivity, luster

Chemical properties

characteristics that show how a substance changes chemically

Ex: flammable, rusts, reacts with water

Solid

definite volume and shape; particles packed in fixed positions

Liquid

definite volume but indefinite shape; particles close together but not in fixed positions

Gas

neither definite volume nor definite shape; particles are at great distances from one another

Plasma

high temperature, ionized phase of matter as found on the sun

10 ways to spot a chemical reaction

1. Bubbles of gas appear

2. A precipitate forms

3. A color change occurs

4. The temperature changes, energy changes

5. Light is emitted

6. A change in volume occurs

7. A change in electrical conductivity occurs

8. A change in melting point or boiling point occurs

9. A change in smell or taste occurs

10. A change in any distinctive chemical or physical property occurs

Solutions

homogeneous mixtures, uniform throughout

What pure substance can only be separated by chemical means into its elements?

coumpounds

How do I know a chemical reaction has occurred?

a chemical change will change the chemical makeup

Precipitate

aqueous (dissolves in water) + aqueous (dissolves in water) = solid