Year 9 Chemistry & Physics 2023

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68 Terms

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What are all three of the subatomic particles?
Protons (+) Neutrons, Electrons (-) 
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Which subatomic particles make up the nucleus of an atom?
Protons and Neutrons
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True or false: Electrons are much bigger and heavier than protons/ neutrons. 
False: Electrons are much smaller and lighter than protons/ neutrons. 
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What is the definition of mass number?
The total number of neutrons and protons (mass number is always the bigger number)
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What is the definition of atomic number?
The number of protons (identifies the element)
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True or false: In an element, the number of electrons are the same number of protons.
True
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How do you find the number of neutrons?
Mass number- atomic number
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Elements
A substance made from the same kind of atom.
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Molecules
A substance made up of two or more of the same atom chemically bonded.
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Compounds
A substance made up of two or more different atoms chemically bonded. Eg. H2O
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Groups
↓Number of valence electrons (electrons in the outermost shell)
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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.
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Periods
 →Number of shells
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Characteristics of noble gases
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* They are in Group 18
* Unreactive
* Stable
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How many electrons are in each shell of an atom (electronic configuration)?
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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.
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Anions
If an atom gains an electron (overall negative charge) eg. Oxygen gains two electron it becomes 02-
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Cations
If an atom loses an electron, (overall positive charge) eg. Oxygen loses 2 it becomes O2+
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Elements in group 1, with a valence electron of 1, will always want to __****__ that electron as fast as possible.
Lose
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Elements in group 7, with a valency of 7, will always want to _____ an electron, making it reactive as well. 
Gain
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Elements in group 8, with a full outer shell, will always be very ______ and ______. 
Stable and unreactive
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Isotopes
Has the same atomic number as the original atom but a different number of neutrons.
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The more neutrons, the more _____ the isotope becomes.
Unstable
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True or false: Carbon 12 is more stable than Carbon 14 as it has an equal number of protons and neutrons.
True
True
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What is the difference between radioactive and radiation?
An unstable isotope is **radioactive**, whilst the energy emitted from nuclear decay is **radiation**.
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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.
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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.
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Acids
A substance that releases hydrogen ions (H+) into an aqueous solution (containing water).
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What are characteristics and an example of acids?
* Sour taste


* PH Less than 7
* Corrosive
* Hydrochloric acid (HCI)
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Bases
A substance that releases hydroxide ions (OH-) into an aqueous solution.
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What are characteristics and an example of bases?
* Taste bitter and soapy


* PH Above 7
* Corrosive
* Ammonia (NH3) Sodium Hydroxide (NaOH)
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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.
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Indicators
They help you find whether a solution is acidic, basic or neutral. They change colours in solutions of different pH.
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Neutralisation reaction
When an acid and a base are mixed.
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The products of a neutralisation reaction
Salt + Water
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Independent variables
The variable that is changed.
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Dependent variables
The variable that is measured.
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Controlled variables
The variable that stays the same.
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Accuracy
It is close to the ‘true’ value of the quantity being measured.
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Precision
How closely two or more measurements are. (The smaller the range the more precise.)
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Energy
Energy is the ability to do work.
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The two main types of energy are:
Potential (Stored)

Kinetic (Moving)
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Which energies are kinetic?
* Heat
* Light
* Sound
* Mechanical
* Electrical
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Which energies are potential?
* Nuclear
* Gravitational
* Elastic
* Chemical
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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.
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In energy flow charts, the first starting energy is always…
potential
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Energy Efficiency
Remember to use units!
Remember to use units!
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Power
The rate at which energy is transformed from one type to another.
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Series circuit
Electrons can only take one path
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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
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Parallel circuit
Electrons can take more than one path
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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
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Current
A measure of the flow of electrons through a circuit every second.
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Current is measured in:
Amps (A) Milliamps (mA)
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Voltage
A measure of how much energy the power source (eg. battery) gives the electrons to move around the circuit.
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Voltage is measured in:
Volts (V)
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Resistance
How a device or material reduces the electric current flow through it.
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Resistance is measured in:
ohms (Ω)
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The equation for resistance is:
__**Resistance (Ω)  = Voltage- Volts (V)/Current- Amps (I)**__
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Conductors
Allow a current to pass through easily, and have low resistance.
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Examples of Conductors
* Silver
* Aluminium
* Copper
* Iron
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Insulators
Have a high resistance where the current does not flow as easily.
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Examples of Insulators
Paper, wood, rubber
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Whenever current flows through a resistor a **…….** effect occurs, this factor can be used in heating elements, such as in a …….
Heating, kettle
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What natural substance is a good conductor and why?
*Saltwater is a good conductor as it contains many ions.*
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Repeatability
When you can obtain the same results in an experiment multiple times under the same conditions (people, equipment, laboratory.)
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Reproducibility
When you can obtain the same results as another group’s experiment under different conditions (different people, equipment, laboratory.)
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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