Science Term1-2

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Voltage

Voltage is a measure of the amount of electrical push that the power source gives to the electrons going around the circuit.

Electric Circuit

A path for electrons to follow, consisting of a power supply, one or more loads, and conductors joining the power supply and loads.

Positively Charged

Any particle or substance that has more protons than electrons is said to be positively charged.

Negatively Charged

Any particle or substance that has more electrons than protons is said to be negatively charged.

Neutrally Charged

Any particle or substance that has equal amounts of positive and negative charge is said to be neutral.

Charged and uncharged substances

The term 'uncharged' is also used to describe neutral particles or substances.Substances usually become charged by the addition or removal of electrons.

Power Supply

Power supply provides the electrical energy

A Load

a load (or loads) in which electrical energy is converted into other useful forms of energy

Conducting path

A conducting path allows electric charge to flow around the circuit.

Convectional Current

electrons flow from negative to positive terminal of a battery.

Electron Current

Electrons flow from negative to positive terminal of a battery

Electric Current

Measure of the amount of electric charge passing a point in an electric circuit every second.The electric current is said to flow from the positive terminal of the power supply to the negative terminal.

Resistance

The conducting paths in the electric circuits in appliances are usually made of metals such as copper so that they have little resistance to the flow of electric charge.

Electron

A subatomic particle that has a negative charge.

Proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom.

Nucleus

An atom's central core, containing protons and neutrons.

Atoms

Basic unit of matter, usually contain an equal number of electrons and protons.

Complete conducting path

Allows electric charge to flow through the circuit.

Wire

Allows a path for current flow.

Two wires crossing over each other

When two wires cross over each other in a circuit

Resistor

An electrical device that resists the flow of electrical current.

Battery (Single cell)

The power source of a circuit with a single cell.

Battery (two cells in a series)

The power source of a circuit with two cells.

Light Globe

Generates light when current flows through.

Ammeter

A device used to measure current in a circuit.

Voltmeter

A device used to measure voltage, or electrical potential energy difference.

2 Wires joined

When 2 wires are joined together in a circuit.

Switch closed

Provides a path for the current to flow when closed.

Switch open

Current flow is stopped when the switch is open.

Diode

A component that only allows current to flow in one direction

Physical Change

A change in a substance that does not involve a change in the identity of the substance

Chemical Change

A change in matter that produces one or more new substances.

Resistance

Electrical resistance is a measure of how difficult it is for electrons to flow through part of a circuit. Resistance produces heat.

Resistance 2

Electrical resistance also determines how much energy is lost by electric charge as it moves through a circuit.

Conductors

Materials that allow electric charges to flow through them easily.

Insulators

Materials that prevent electric charges from flowing through them easily.

Series Circuit

A circuit with the components joined one after the other in a single continuous loop, if any one part of the circuit is faulty, the connecting path is broken and nothing in the circuit will work.

Parallel Circuit

A parallel circuit has more than one path for electricity to flow through. If one of the paths has a break in it, the others will still work.

Measuring Current

The size of the electric current in an electric circuit can be measured by determining the amount of electric charge passing a particular point in an electric circuit every second.

Ohms law

Ohm's law states that the current in a circuit is directly proportional to the voltage/potential difference. 

R

Represents resistance and its unit is the ohm (Ω) R= V (voltage) ÷I (current)

V

Is the voltage drop in volts.

I

Is the electric current in ampheres (A).

V= IxR

I= V÷R R=V÷I

Ohm’s law in series

Current through the circuit is always the same. 

Voltage through the circuit is divided amongst the components of the circuit.

The total resistance is the sum of the resistance of all the components. 

Ohms law in parallel

Current is divided amongst the different branches in the circuit.

◦Voltage across the branches are the same. 

Magnets

Magnets attract iron and alloys containing iron. They also attract alloys containing nickel and cobalt.

All magnets, no matter what their shape, have a north pole and a south pole.

Like poles of magnets repel while unlike poles attract.

Permanent magnets retain their magnetism at all times.

Temporary magnets lose their magnetism when removed from other magnets.

Magnetic field

The region in which a magnetic force exists is called a magnetic field.

Resistor

Resistors are used in electric circuits to control the voltage and current. They can have a fixed resistance or can be variable like those in volume controls.

Voltmeter

A voltmeter is used to measure the voltage gain across the terminals of a power supply or voltage drop across parts of an electric circuit.

Random eror

Random error is an error that occurs due to estimation when reading scales, or when the quantity being measured changes randomly. 

Systematic error

Systematic error is consistently high or low due to the incorrect use or limitations of equipment.

Systematic errors can be eliminated by knowing how to use the equipment correctly.

Compass

The compass needle sings toward the geographical north pole or the magnetic south pole.

A compass works the way it does because Earth has a magnetic field that looks a lot like the one in a magnet.

Electromagnet

An electromagnet is a temporary magnet consisting of a coil of wire and an iron core.

The coil of wire is called a solenoid, when the electric current flows in the coil, a magnetic field is produced.

Without the iron core, a magnetic field would still be created. However, it would not be as strong.

Static Electricity

Static electricity is generated by friction between two insulating materials. When the materials are rubbed together, electrons are removed from atoms within the materials, giving rise to a static electric charge.

Static electric shock

Static electricity occurs more often during the colder seasons because the air is drier, and it’s easier to build up electrons on the skin’s surface.

AC Current (Alternating current)

Electric current flows in two ways as an alternating current (AC) or direct current (DC).

Electrons keep switching directions, going forward and then backwards in AC. 

DC Current (Direct current)

Electric current flows in two ways as an alternating current (AC) or direct current (DC).

In DC, the electrons flow steadily in a single direction.

Physical Change

Change in shape, size, appearance or state. 

Chemical Change

When a new substance is created.

Reactants

The original substances in a chemical reaction are called the reactants.

Products

The new substances that are formed during a chemical reaction are called the products.

Word Equations

Reactant + reactant --> product + product

eg. Iron reacts with flourine gas to produce iron flouride. 

During a chemical reaction…

During a chemical reaction atoms are rearranged and mass is conserved.

According to the Law of Conservation of Mass, the mass of the reactants before the reaction needs to equal the mass of the products after the reaction. This applies to the number of atoms as well. The number of atoms before a reaction need to equal the number of atoms after the reaction. 

Exothermic Reaction

Chemical reactions that release energy are called exothermic reactions.

The energy released comes from the rearrangement of atoms. There is l

ess energy stored in the chemical bonds in the products than there was in the reactants. 

Endothermic Reaction

Chemical reactions in which energy is absorbed from the surroundings are called endothermic reactions.

There is more energy ‘stored’ in the chemical bonds of the products than there was in the reactants.

Acids

Sour tasting, corrosive (eats away solid objects), turns litmus paper red, turns bromothymol blue yellow.

Bases

Bitter tasting, feels soapy or slippery, can be corrosive and breaks down fat. Bases turn litmus paper blue and bromothymol blue a bluish-purple.

Alkali

Bases that can dissolve in water.

Red Cabbage

Red Cabbage is a natural pH indicator.

The pH scale

The pH scale ranges from 1-14. <7 is acidic and >7 is basic. At pH 7, a substance is said to be neutral. Acids and bases can be graded from strong to weak. For example, a strong acid has a very low pH (pH 0 or 1) and a strong base has a very high pH (pH 13 or 14). 

Universal Indicator

The pH of a substance can be measured using a pH meter or a special indicator called universal indicator. Universal indicator is a mixture of indicators and it changes colour as the strength of an acid or base changes. 

Neutralisation Reaction

Acid + base → salt + water, neutralisation a reaction between an acid and a base. A salt and water (a neutral liquid) are the products of this type of reaction. To neutralise something means to stop something from having an effect.

Indigestion

The hydrochloric acid in your stomach helps to break down the food you eat. It is a very strong acid, with a pH of less than 1.5.

Indigestion 2

But if you eat too quickly, or eat too much of the wrong food, the contents of your stomach become even more acidic. You feel a burning sensation because of the corrosive properties of the acid.

Antacid Tablets

Antacid tablets contain weak bases like aluminium hydroxide, magnesium carbonate, and magnesium hydroxide to neutralize stomach acid. Examples of chemical word equations:
hydrochloric acid + aluminium hydroxide → aluminium chloride + water
hydrochloric acid + magnesium hydroxide → magnesium chloride + water
hydrochloric acid + magnesium carbonate → magnesium chloride + water + carbon dioxide

Carbon Dioxide

One product of this last reaction is carbon dioxide gas. You burp to get the gas out of your stomach.

The Law of Conservation of Mass

Mass cannot be created or destroyed in a chemical reaction.