Physical Science Notes
Properties of Matter
Matter-the material or “stuff” everything is made of
Physical properties-a way of describing objects
Some properties scientists use:
1. volume- how much space something takes up
2. mass-how much matter is inside (balloons have a low mass and a brick has a higher mass)
3. shape
4. states of matter (see below)
3 states (forms) of matter:
1. solid-matter has a definite shape and volume
2. liquid-matter has a definite volume but no definite shape (it takes the shape and volume of whatever the container is).
3. gas-matter has no definite shape or volume
Chemical property-the ability of a substance to change into a new substance with different properties
Physical/Chemical Changes
Physical change- a change in one or more physical properties. It can change back ( heating or cooling can change water from one state to another and the change is reversible)
Examples:
Chemical change- When a new material is made by combining two or more materials, it has chemical properties that are different from the original materials. It can’t change back. Examples: burning paper, combining vinegar and baking soda
Examples:
Bubbles are formed fire
Chemical Reaction-what causes the chemical change. The atoms in molecules are rearranged to form new molecules.
Signs there’s been a chemical change:
Light or heat is made, color change, gas is produced, a new odor, or sound.
Thermal Energy
Thermal energy-the energy of the movement of molecules in a substance (heat)
*The faster the molecules move, the warmer it is.
*The slower the molecules move, the less heat it has
*Heat is the movement between 2 things with different temperatures (holding an ice cube).
*Heat always moves from the hotter object to the colder object.
The heat energy of a substance is determined by how active its atoms and molecules are. A hot object is one whose atoms and molecules are excited and show rapid movement. A cooler object's molecules and atoms will be less excited and show less movement. When these guys are in the excited state, they take up a lot of space because they're moving around so fast. When the atoms and molecules settle down, or cool down, they take up less space. /If a HOT high-energy atom comes into contact with a cool low-energy atom, the excited atom will loose some of its energy to the cool atom. The two atoms will settle into an energy level that's between where they each started out. This is called thermal equilibrium.
Temperature- the measurement of how fast the molecules are moving in matter. The faster the molecules, the higher the temperature. The slower the molecules, the lower the temperature. The liquid inside the thermometer expands and goes up the tube as it gets hotter.
Conduction-the movement of heat between 2 objects through direct touching. As one molecule is heated it begins to move and shake rapidly. As it does so, it passes some of its heat energy to other molecules around it. Through this process, all the molecules of an object pass heat from one to another, until they are all hot.
Conductors/Insulators
Conductor-objects that allow thermal energy (heat) or electricity to move through them easily
Examples:
Insulator-objects that don’t allow heat or electricity to move through it well
Examples:
Convection -the transfer of heat by the actual movement of the heated material.
Example: Boiling water
Radiation-Any high-speed transmission of energy in the form of particles or electromagnetic waves
Example: heat from the Sun
Light
Light-a form of energy that travels in straight lines in all directions. It can behave in one of 3 ways when it encounters an object.
1. Reflection-light bouncing off an object to our eyes
2. Absorption-light can be absorbed by objects. The object soaks it in like a sponge.
3. Refraction-light is bent when it passes from one substance to another.
Example:
**Rainbows are formed by refraction. Sunlight passes through water droplets in the air, and the water droplets make the light bend. Some of the colors bend more than other and they are separated to form a rainbow.
Objects can be:
Transparent-(clear) light rays can pass right through
Example:
Translucent-light rays can pass though, but they stop going in straight lines and scatter many directions
Example:
Opaque-light can’t pass through it at all
Example:
Sound
Transmission-how sound moves
1. Sound is made by vibrations.
2. These vibrations make the air particles next to it vibrate, which starts a wave, which travel to our ears.
3. Unlike light, sound needs a medium (like air) to travel through.
Reflection-When sound is reflected it bounces around (like an echo).
Example:
Absorption-When a sound is absorbed (like the acoustic tiles in the music room).
*We are surrounded by sound vibrations, but we can only hear some of them.
Pitch-How fast or slow the vibrations are
The faster the vibration, the higher the pitch.
The slower the vibration, the lower the pitch.
Whistle-high pitch tuba-low pitch
Electrical Energy
Electrical energy is the flow of electrons between atoms (jumping from atom to atom).
Circuit-a complete loop that electrons flow though. To make a simple circuit you must have:
*power source (battery)
*wire (to carry the electrons)
*light bulb
The electrons from the negative end of a battery are pulled through the wire. They pass through the light bulb and light it up. They pass through the bottom of the bulb then are then pulled into the positive end of the battery to make a complete circuit.
Conductor-a material that’s good at carrying electricity.
Example:
Insulator-a material that’s not good at carrying electricity.
Example:
*Electricity and magnetism are a lot alike-both have a + and - charge.
*Electric currents make a magnetic field and magnetic fields can be made to make an electrical current.
*Electrical currents can produce:
Thermal energy
Example:
Light.
Example:
Sound.
Example: