Physical Science Unit 2

Crest

The highest distance from equilibrium

Trough

The lowest distance from equilibrium

Amplitude

The distance a wave moves away from equilibrium (height of wave)

Frequency

The amount of times a wave passes through equilibrium, normally counted by the number of crests passing through the space

Wavelength

The distance between two crests (or troughs) of wave

Wave Speed

How fast the wave is (only changes with change in medium)

Reflection

Waves tend to bounce off of surfaces

Refraction

Waves tend to bend/change speeds when they travel through a new medium

Diffraction

When waves pass through an opening THE SAME SIZE or SMALLER than the wave, it will fan out in different directions

Interference

Waves tend to interfere with each other when they collide, either constructively building each other up or destructively breaking each other down

You get lost at Walmart when you turn a corner and your mom calls your name. As the sound travels around the corner, it will experience…

Diffraction

The image to the right represents a sound wave passing through a room. The crest of each wave is represented by the white shaded portions and the troughs by the dark shaded portions. What would the arrows be referring to?

Wavelength

You buy a brand-new dreamlight pillow pet after you saw an ad on TV. You flip the color from yellow to blue. Which of the following state the correct difference between the lights.

We decreased wavelength and increased frequency

Photons

particles of light that lack MASS and CHARGE but carry ENERGY

The photoelectric effect

light is both a wave and a particle due to light’s ability to knock off electrons being dependent on FREQUENCY!!!

In the experiment UV light was able to discharge an electroscope based on frequency, NOT based on brightness (amplitude)

The photoelectric effect teaches us that light is a particle. For said particles (photons) to become powerful enough to discharge an electroscope, what would we have to do to the light we are shining?

Increase Frequency

Which of the following statements are true due to your understanding of the photoelectric effect?

None of the above

Conductors

Types of matter which always conduct electricity (Ex. Metal

Ionic Conductors

Types of matter which do not conduct electricity until dissolved into another substance (Ex. Salt in Water)

Nonconductors

Substances which do not conduct electricity (ex. Sugar)

Which of the following graphs demonstrate the changes of states between solid, liquids, and gases based on temperature?

It looks like steps

I place Arsenic (As/33) Selenium (Se/34), and Bromine (Br/35) molecules all in a box and increase the temperature to 100 degrees which causes all the molecules to move in random motion. Which statement is true?

They all have the same kinetic energy despite having different speeds

The Continuous Model

The idea that matter can be divided as many times as you like, and you will still have the same elements and molecules.

Brownian Motion + Molecular Model

experimental proof that particles in matter constantly move in a disordered fashion

THERE MUST BE SMALLER PARTS!

Explains: 

> Temperature

> States of Matter

> Pressure & Density

Thomson’s Gas Tube

• Thompson put gases into a tube and charged the ends of the tubes.

He found that parts of gases would travel to each end, showing charges. He also found that the negative end (that the positive particles were attracted to) weighed much more than the positive end (holding the negative particles)

The Plum Pudding / Chocolate Chip Model 

Positive mass (dough) with floating electrons (chocolate chips)Explains: 

> there are charged particles within the atom

> much more positive mass than negative

Rutherford’s Gold Foil Experiment

Rutherford shot Alpha (positive) particles at thin gold foil. His expectation was that all the alpha particles would fly through. What actually happened? Most passed through, however a small number bounced off onto the walls.

Solar System Model

• Atoms have a nucleus, this nucleus contains all the positive charge

• negatively charged parts do not exist within the nucleus

• Rutherford concluded that they must be orbiting the nucleus, like the solar system (not in discrete orbits)

Explains:

> concentration of charge

Flaws:

> why don’t the electrons emit light?

> why don’t the electrons fall in?

> can’t explain emission spectra

In the Thomson gas discharge tube experiment, we saw that masses of gases were dispersed across two sides of a tube because of charges. Which of the following statements are true based off this experiment?

The positive mass in an atom is much larger than the negative mass, despite the similar AMOUNT of charge

Rutherford’s experiment consisted of shooting positive alpha particles through a thin sheet of gold foil. For the Plum Pudding model to be wrong, what must have happened?

A majority would pass through, but some would bounce off in different directions due to collisions with the nucleus

Which of the following correctly describes brownian motion?

Movement of particles based on smaller unseen molecules running into the particle

Discrete Spectrum

Only certain light colors can be demonstrated when energy is let off

Continuous Spectrum

All light colors should be demonstrated

SOLAR SYSTEM PROBLEM

f atoms can exist in any part of an orbit at any time, theoretically all matter would be constantly producing white light (the continuous spectrum) while in reality atoms only demonstrate certain colors when energy is released

Bohr Model

• Electrons orbit in specific, discrete levels

• They can jump from different levels in the orbits to emit or absorb light

Explains:

> emission spectrum (only Hydrogen)

Flaws:

> why don’t the electrons emit light?

> why don’t the electrons fall in?

> can’t fully explain emission spectra

Why could the Bohr model explain more correct color emissions while the solar system model could not?

The Bohr model divided the atom into energy levels while the solar system model let them all sit at random undetermined levels

The Uncertainty Principle

 You cannot know everything about an electron.
You can either know position or momentum.If you attempt to observe an electron when it passes through the two slits it will behave like a particle, when not watching it behaves like a wave.

Orbits

In the Bohr and Solar System models, a set path which orbits around the nucleus.

Orbitals

A standing wave of probability, represents an area of space in which an electron COULD be, however due to the uncertainty principle we have no idea EXACTLY where it is (NOT A PATH)

Which of the following best describes an orbital?

A standing wave of probability which demonstrates a region in which it will most likely be

The Octet Rule

The majority of elements on the periodic table seeks to have a full outer shell (or to remove all the electrons from the outermost shell to remove it and make the next layer the most full

Family

Elements in the same column, behave the same as you go down a column

Period

Elements in the same row,
behave differently as you go along the row

Ionization Energy

The energy required to remove an electron from an atom. Electrons at the top right of the table hold more tightly to their electrons and don’t want to become ionized (lose an electron)

Atomic Radius

The distance of the outermost electrons from the nucleus. While the mass increases left to right, the number of protons and electrons also increase creating a stronger pull between the two. This makes the atom’s radius (and atomic volume) smaller.

If I were to compare the chemical properties of multiple elements, which two would behave the most similarly? How do you know?

S and Se because they are in the same column