# 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