# YEAR 7: CHEMISTRY FINAL NOTES

## Investigatory Skills

### Keywords

** Control Variable **- the thing(s) you keep the same

**Independent Variable** - the thing you change

**Dependant Variable** - the thing you measure

**Correlation** - a relationship between two variables

**Meniscus **- If the bottom of the meniscus is between 25 and 26, so, we call the meniscus of this 25.5

**Scientific question **- A specific question which can be tested

**Anomalies **- An odd result in a set which does not fit in

### Concepts and Methods

**How to calculate a mean **- Add up all of the numbers in a data set then divide the total by the number of items.

**How to calculate a percentage **- Divide the numerator of a number by the denominator and multiply it by 100. E.g. 2 / 5 x 100

**Converting between meters and centimetres **- Multiply the number of meters by 100 and change the units to cm

**How to describe a correlation **- As the (independent v.) increases, the (dependant v.) (increases/decreases).

### Graph vs. Table

Graphs go up in 1, 2, 5 and 10’s. You must label the axis with units and it must have a line of best fit. The independent variable goes on the x axis / horizontal line and the dependant variable goes on the y axis.
The independent variable must go on the left column of the table and the dependant variable goes on the right column. There should be units next to the heading of the dependant variable and the right column should be in increasing order.
### Types of Graph and Bar Chart

**Bar Chart** - When one of the variables is not a number (e.g. colour) (categoric data)

**Best Fit Graph**- When we plot points and draw a line of best fit that shows the pattern of points

**Scatter Graph** - When we plot points, but, there is no clear pattern so we do not draw a line of best fit

## Particle Theory

### Properties of Particles

**Solids:**

Strongly attracted
Vibrate on the spot
Touch each other
Ordered
**Liquid:**

Medium attracted
Touch each other
Move fairly freely
Arranged randomly
Slide over each other over time
**Gas:**

Loosely attracted
Arranged randomly
Move freely in all directions
Don’t touch each other
Changes of State
Solid > Gas = Sublimation
Solid > Liquid = Melting
Liquid > Gas = Boiling
Liquid > Solid = Freezing
Gas > Liquid = Cooling
Gas > Solid = Deposition
Properties of State Changes
Melting
Particle distance increases
Energy of particles increases
Forces between particles increases
Freezing
Particle distance decreases
Energy of particles decreases
Forces between particles decreases
Boiling
Particle distance increases
Energy of particles increases
Forces between particles increases
Reactions
Keywords
Exothermic - Exothermic reactions transfer energy from the reactants to the surroundings. They feel hot. Exo is similar to exit and heat is exiting to the surroundings.
Endothermic - Endothermic reactions take in energy from the surroundings. They feel cold. End is similar to in-do and heat is entering/going in,
Fire Triangle - A fire triangle shows 3 things that a fire can’t survive without. These things are heat, oxygen and fuel.
Element - An atom of only one type
Compound - Two or more elements chemically bonded
Conservation of Mass - If you do any reaction, the total mass of the reactants is equal to the mass of the products.
Combustion
The only product of combustion is an oxide. E.g. Magnesium + oxygen = Magnesium Oxide