Year 9 Chemistry & Physics 2023

What are all three of the subatomic particles?

What are all three of the subatomic particles?

Protons (+) Neutrons, Electrons (-)

Which subatomic particles make up the nucleus of an atom?

Protons and Neutrons

True or false: Electrons are much bigger and heavier than protons/ neutrons.

False: Electrons are much smaller and lighter than protons/ neutrons.

What is the definition of mass number?

The total number of neutrons and protons (mass number is always the bigger number)

What is the definition of atomic number?

The number of protons (identifies the element)

True or false: In an element, the number of electrons are the same number of protons.

True

How do you find the number of neutrons?

Mass number- atomic number

Elements

A substance made from the same kind of atom.

Molecules

A substance made up of two or more of the same atom chemically bonded.

Compounds

A substance made up of two or more different atoms chemically bonded. Eg. H2O

Groups

↓Number of valence electrons (electrons in the outermost shell)

Groups tell us the reactivity of the element. Which groups in the periodic table are the most unstable?

Group 1 and Group 17 are the most unstable.

Periods

→Number of shells

Characteristics of noble gases

• They are in Group 18

• Unreactive

• Stable

How many electrons are in each shell of an atom (electronic configuration)?

How does a flame test identify metallic elements?

If we give energy to some metallic atoms, by heating them, their electrons jump from one electron shell to another. As they fall back to their normal state they release the excess energy in the form of light. Each atom emits a unique colour of light and thus the flame test can be used to identify different metals.

Anions

If an atom gains an electron (overall negative charge) eg. Oxygen gains two electron it becomes 02-

Cations

If an atom loses an electron, (overall positive charge) eg. Oxygen loses 2 it becomes O2+

Elements in group 1, with a valence electron of 1, will always want to **** that electron as fast as possible.

Lose

Elements in group 7, with a valency of 7, will always want to _____ an electron, making it reactive as well.

Gain

Elements in group 8, with a full outer shell, will always be very ______ and ______.

Stable and unreactive

Isotopes

Has the same atomic number as the original atom but a different number of neutrons.

The more neutrons, the more _____ the isotope becomes.

Unstable

True or false: Carbon 12 is more stable than Carbon 14 as it has an equal number of protons and neutrons.

True

What is the difference between radioactive and radiation?

An unstable isotope is radioactive, whilst the energy emitted from nuclear decay is radiation.

Half-life

The time it takes for half (50%) of the isotope to decay. Something stable decays really slowly, whilst something unstable decays really quickly.

Law of Conservation of Mass

Atoms cannot be broken down or destroyed, they can only be reshuffled to form new substances. What is on one side of the equation must be on the other side.

Acids

A substance that releases hydrogen ions (H+) into an aqueous solution (containing water).

What are characteristics and an example of acids?

• Sour taste

• PH Less than 7

• Corrosive

• Hydrochloric acid (HCI)

Bases

A substance that releases hydroxide ions (OH-) into an aqueous solution.

What are characteristics and an example of bases?

• Taste bitter and soapy

• PH Above 7

• Corrosive

• Ammonia (NH3) Sodium Hydroxide (NaOH)

What does a pH scale measure?

The concentration of hydrogen ions (H+) in a solution. In an acidic solution, there are more hydrogen ions than hydroxide ions. In an alkaline solution, there are more hydroxide ions than hydrogen ions.

Indicators

They help you find whether a solution is acidic, basic or neutral. They change colours in solutions of different pH.

Neutralisation reaction

When an acid and a base are mixed.

The products of a neutralisation reaction

Salt + Water

Independent variables

The variable that is changed.

Dependent variables

The variable that is measured.

Controlled variables

The variable that stays the same.

Accuracy

It is close to the ‘true’ value of the quantity being measured.

Precision

How closely two or more measurements are. (The smaller the range the more precise.)

Energy

Energy is the ability to do work.

The two main types of energy are:

Potential (Stored)

Kinetic (Moving)

Which energies are kinetic?

• Heat

• Light

• Sound

• Mechanical

• Electrical

Which energies are potential?

• Nuclear

• Gravitational

• Elastic

• Chemical

Law of Conservation of Energy

Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another.

In energy flow charts, the first starting energy is always…

potential

Energy Efficiency

Remember to use units!

Power

The rate at which energy is transformed from one type to another.

Series circuit

Electrons can only take one path

Series circuit characteristics

• All globes glow with the same brightness

• Globes share the battery voltage, so the more globes the dimmer

• If one globe burns out, all the other ones burn out as well

Parallel circuit

Electrons can take more than one path

Parallel circuit characteristics

• All globes glow with the same brightness, but individual globes are brighter than those connected in series

• Use more energy so the battery runs out faster

• If one globe dies, the others will still glow

Current

A measure of the flow of electrons through a circuit every second.

Current is measured in:

Amps (A) Milliamps (mA)

Voltage

A measure of how much energy the power source (eg. battery) gives the electrons to move around the circuit.

Voltage is measured in:

Volts (V)

Resistance

How a device or material reduces the electric current flow through it.

Resistance is measured in:

ohms (Ω)

The equation for resistance is:

Resistance (Ω)  = Voltage- Volts (V)/Current- Amps (I)

Conductors

Allow a current to pass through easily, and have low resistance.

Examples of Conductors

• Silver

• Aluminium

• Copper

• Iron

Insulators

Have a high resistance where the current does not flow as easily.

Examples of Insulators

Paper, wood, rubber

Whenever current flows through a resistor a ……. effect occurs, this factor can be used in heating elements, such as in a …….

Heating, kettle

What natural substance is a good conductor and why?

Saltwater is a good conductor as it contains many ions.

Repeatability

When you can obtain the same results in an experiment multiple times under the same conditions (people, equipment, laboratory.)

Reproducibility

When you can obtain the same results as another group’s experiment under different conditions (different people, equipment, laboratory.)

The characteristics of a fair experiment:

• All the variables in an experiment must be considered and controlled

• Only one variable may be altered at a time