Chemical Changes, Physical Changes, and Mixtures

Chemical Changes

One where a substance transforms into a new substance with different properties in which the chemical composition is altered (the compound is no longer the same as before)

e.g. A burning match

C3H8 + 5O2 -> 3CO2 + 4H2O

To Answer Chemical Equation on Exam Remember

1. Law of Conservation of Matter: Matter cannot be created or destroyed, it changes, so everything that happens on one side of the equation has to be don on the other side

2. Know What the Numbers Represent

C3 <- 3 Carbons

and number in front of variables (compounds) is the coefficient and that's the only number we'll add to it to balance

Catalyst

Something that start a chemical reaction such as a spark

-It doesn't have to be fire that starts a chemical reaction, there are certain types don't

BUT OFTEN THEY DO SHOW A FIRE WHEN A REACTION TAKES PLACE

If a question ask, "Which one of these is a chemical reaction?"

Look for the one with fire

Balancing Chemical Equation Example

IF YOU GET TO THIS CARD, BALANCE A CHEM EQUATION OF CHOICE

1. Things cannot just disappear

2. Increase on one side, increase on other. Cannot take away

3. Everything on one side happens to next and only change coefficient

Mixture

A material that cannot be separated by physical means into two or more substances

The two types to know: Solution and Suspension

Mixture: Solution

A homogenous mixture where one substance has completely dissolved into the other

e.g. Saline Solution

The distribution of the salt through the water is even making it HOMOGENOUS

However, if you boiled water and changed it's state, water evaporates, but salt left behind. (salt only goes if chemically bonded)

Mixture: Suspension

A system in which small particles are kept dispersed by agitation or molecular motion in the surrounding medium.

e.g. Muddy water in a river

Churning action of water in the river that gets the mud and water mixed together, but if you scooped out a glass of that anf set it on counter an hour later it would separate with all the water on top and mud on the bottom. Separates because there's no longing agitation

Physical Change

A change from one state to another without a change in chemical composition

Think Three States of Matter

Solid

Liquid

Gas

e.g. melting ice

e.g. boiling water to steam

Three States of Matter

Solid, liquid, gas

How to Differentiate Between the Three States of Matter Using 2 Basic Properties

Can it be compress?

and

Can it take the shape of its container?

Solid (Coldest)

CANNOT be compressed

DOES NOT take the shape of its container

e.g. clay in a container will return/keep its shape

Liquid (In the Middle)

CANNOT be compressed

DOES take the shape of its container

e.g. Plastic water bottle full of water. If you stomp on it the cap poops off because the water has to go somewhere. When in its bottle, water takes the bottle's shape.

Gas (Hottest)

CAN be compressed

DOES take the shape of its contained

e.g. Air made up of several gasses or different elements like Nitrogen, CO2, Oxygen, and more.

You have it in a plastic bottle, squeeze the bottle, the cap won't come off because what's inside can get compressed and fills out whole inside container even tho can't see it to take its shape.

2 Reasons Something Changes States

Temperate and Pressure

Every substance has a unique boiling point and freezing point

e.g.

Water Boils 212F at sea level

Water Freezes 32F at sea level

This isn't true if you change altitude. Why? because Pressure!

Mass pushes down

with 14.7 pounds of forces on our bodies, but we can't feel that

At sea level

ALL atmosphere is pushing down

But if you go up 10,000 feet, 10,000 LESS feet of atmosphere will push down on you.

Less atmosphere, pushing down, Less pressure

More pressure

wants to be a solid

Less pressure

wants to be a gas

Why more pressure is solid and less pressure is gas?

Temperature is molecular motion

The Faster a molecules move, the hotter the thing is

Put pressure, harder for them to move

Pressure cools things and causes them to stay in place, like a solid.

Gas Law 1: Charle's Law (There's a direct relationship between temperature and volume)

As temp goes up, volume goes up

As temp goes down, volume goes down

Direct correlation between these two things

e.g. this is why when boiling water with a lid on, the lid rattles around because as gas in the pt expands

Temperature raising and the volume increasing needs to go somewhere

Eventually, build ups enough pressure to lift lid and escape

Gas Law 2: Boyle's Law (Inverse relationship between pressure and volume)

As pressure goes up, volume goes down

As pressure goes down, volume goes up

Boyle's Law As Pressure does Down, Volumes goes Up

When a kid loses a Helium balloon.

Balloon, flow, tire and higher there is less atmosphere

So less atmosphere = Less pressure

So with less pressure, you get more volume

(Opposite of pool)

The balloon gets bigger and bigger as pressure goes down the higher and higher it goes into the atmosphere

Eventually, the balloon gets so big it's rubber can no longer tolerate it so it pops and falls back to

OR THINK MARSHMALLOW IN SYRINGE, when the pressure went up (pulled back on syringe finger covering top) the volume went up by marshmallow stretching out

Boyle's Law As pressure goes up, volume goes down Example

In a swimming pool with goggles on, and you have a balloon,

You take the balloon and swim down to the deep end of the pool.

If the balloon is big on the surface, it's shrunk at the bottom of the pool because water pressure compresses air/gas in the balloon.

So as pressure increases outside, the volume of gas decreases

THINK MARSHMALLOW IN SYRINGE, when the pressure went up (lifted finger off top) the volume goes down the marshmallow shrunk