Science Revision

Definition of Element

Substances where there are only one type of atom

Compound Def

Substances which consists of two (or more) atoms joined together

Heterogenous Mixture Def

Substances which contain multiple different compounds

Examples of Heterogenous mixtures

Oil and water, vodka, pizza, salad, concrete

Homogenous Mixture Def

Substances which contain multiple different pure atoms

Example of Homogenous Mixtures

Air(mixture of different gases), Steel(Iron and Carbon), Saltwater(Salt dissolved in water)

What is the format of electron shells

2,8,8,2

Covalent Def

A chemical bond where atoms share electrons to become stable

3 Properties of Covalent bonds

Any combination of: They have a low melting and boiling point, form molecules, poor conductors, covalent bonds are held together weakly and can be broken apart easily

Def of Ionic Bond

Atoms transfer electrons to the other, bonding

3 properties of Ionic Bonds

forms crystalline solids, have high melting points, conducts electricity in solution, they have strong bonds and require a lot of energy to break them apart, solid at room temperature

Types of elements in Ionic Bonds

Metal + Non-Metal

Types of elements in covalent bonds

Non-Metal + Non-Metal

What is an Acid

An acid is a chemical substanct that is defined as a molecule, or ion, that can donate a proton when dissolved in water. It is represented as (H^+)

What are some properties of acid

They are typically sour tasting and react with bases to form salts.

How is the strength of an acid determined

The strength of an acid is determined by its ability to donate protons.

Chemical Change Def

When the composition of a substance is changed, which requires the breaking and forming of chemical bonds. This results in the rearranging of atoms in substances to form the products of a chemical reaction, which are brand new molecules which cannot be easily reverted to their original state.

Examples of chemical change

Burning wood, rotting banana, mixing vinegar and baking soda, fireworks, etc

Physical Change Def

The material involved in the change is structurally the same before and after the change. Physical change can affect texture, shape, temperature, and a change in the state of matter

Examples of Physical Change

Melting ice, chopping wood, shredding paper, mixing grey and green marbles, etc

What it the Law of conservation of mass

Mass cannot be created or destroyed, it can only be rearranged

How are worded equations written

e.g. Carbon Dioxide + Water → Glucose + Oxygen (Photosynthesis)

What is Collision Theory

For a reaction to occur, particles must crash into each other in the right way and with enough energy. Not every crash leads to a reaction, only ones with enough force to break old bonds and create new ones. Those are called successful collisions.

what are two ways that the rate of reaction can be measured

There are two ways

• measure the rate at which a reactant is used up

• Measure the rate at which the product is formed

What kind of rate of reaction do reactions that happen quickly have

high rate of reaction

What kind of rate of reaction do reactions that happen slowly have

low rate of reaction

How to calculate/measure the rate of reaction

reaction rate = change in mass of reaction(or product)/ time

Endothermic reaction def

chemicals that absorb(or use) energy are called endothermic. In endothermic reactions as more energy is absorbed new bonds are formed in the products.

Examples of endothermic reactions

Photosynthesis, Evaporating liquids, melting ice, dry ice

Exothermic reaction def

A chemical reaction that releases energy by light or heat, the opposite of an endothermic reaction. expressed in a chemical equation as Reactants → Products + Energy

Examples of exothermic reactions

Combustion, Respiration, Neutralisation (mixing an acid and base)

Combustion Reaction def

Oxygen reacts with another compound to form carbon dioxide, water and heat

Corrosion Reaction def

The natural degradation of a material, almost always a metal, due to oxidation. AKA rust

Precipitation Reaction def

A chemical reaction where two or more soluble substances in a solution combine to form an insoluble solution called a precipitate

Neutralisation Reaction def

A chemical reaction between and acid and a base. This produces salt and water

Decomposition Reaction def

a chemical reaction where a single compound breaks down into two more simpler substances

Reliability Def

the consistency of an experiments results, meaning the experiment would produce similar outcomes if repeated under the same conditions

ways to improve reliability

Increasing the number of trials, controlling the variables, and using calibrated equipment

Accuracy def

How close a measurement or experimental result is to the true or accepted value

Ways to improve Accuracy

Minimise systematic and random errors through calibrating equipment, keep experiment procedures the same, as well as variables.

What are things needed on a graph

Axes, Scale, Data Points, Legend, Graph Titile, Graph Numbering, and Line of best fit if neccesary

What is activation energy

The energy required to break a chemical bond

What is a Catalyst

A substance that speeds up a chemical reaction, lowers the temperature or pressure needed to start one

What is an SI unit

They are an international system of measurements that are used to standardise measures

What is a Scalar quantity

quantites that are fully described by magnitude alone

What is a vector quantity

Any quantity that has both magnitude and direction

Distance isssss

the total length of the path travelled

Displacement isssss

How far away an object is from its original position

Distance =

Speed x Time

Speed issss

How quickly an object is moving

Velocity issss

The rate at which an object changes its position, basically just speed but with direction

What is an easy way to convert m/s to km/h

x3.6

What is an easy way to convert km/h to m/s

÷3.6

What is instantaneous speed

How fast an object is travelling at a given moment in time

speed =

distance/time

time =

distance/speed

velocity =

displacement/time

displacement =

time x velocity

time = 

displacement/velocity

A force can be described as _____

A push or a pull

When a force can act without touching the object what type of force is it

non contact

What are some examples of contact forces

tension, normal reaction force, friction

In which direction does air resistance always act

against the direction of movement

What are some non contact forces

Magnetic force, gravitational force, electrical force

What is Mass

The amount of matter an object contains, measured in kg

What is Weight

Force exterted on an object due to gravity, measured in N, newtons

Weight = 

mass x gravitational field strength

What is Newtons 1st Law

The law of motion, AKA law of inertia

What does newtons 1st law mean

An object at rest will remain at rest, and an object in motion will continue in motion unless acted upon by an unbalanced force

What is inertia

inertia is an objects resistance to a change in its motion

What is newtons 2nd law

To move a mass you need force

What does newtons second law mean

the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass

Force =

Mass x acceleration

What is newtons 3rd law

Action reaction law

what does newtons 3rd law mean

For every action there is an equal and opposite reaction

how old is the earth

4.6 bn years old (she olddddd)

What is an eon

a measurement of time, what the age of the earth is measured in, about a billion years

How do we know the age of the earth

due to rock records

What are fossils

Remains, imprints or evidence of prehistoric plants and animals that have fossilised

Where are fossils found

In sedimentary rock, like sandstone, limestone or shale

How does carbon dating work

using properties of carbon radioisotopes to determine the age of an object containing organic material

What is biodiversity

The full variety of organisms and number of different species in a given area

What is evolution

a change in living organisms over a long period of time (usually), sometimes resulting in an entirely new species

What is an adaptation

A trait that improves an organisms ability to survive and reproduce in an environment

What are the 3 different types of adaptations and what do they reference

Structural (how organism is built)

Physiological (how organism functions/processes)

Behavioural (how organism behaves or acts)

What are 2 important observations charles darwin made on that boat (HMS beagle)

He noticed finches on the island were similar to the finches from the mainland, but each showed certain characteristics that helped them to gather food more easily in their specific habitat

Tortoises on different islands had different shell shapes indicating that they had evolved to suit their environment

ancient fossils of extinct animals

marine fossils found high on mountains

What is a hypothesis

a tentative, testable explanation for a phenomenon in the natural world

What is a fact

scientific observation that has been repeatedly confirmed. fro practical purposes it is considered ‘true’, however it still can be modified if new evidence is provided.

What is a theory

carefully though tout explanation for observations of the natural world that has been constructed using the scientific method

What is a law

statements, based on repeated experiments or observations, that describe or predict a range of natural phenomena

What did jean baptiste lamarck believe (he was stupid)

that body parts that were used were passed on to offspring and those that weren’t weren’t, referred to as acquired characteristics. NOT SUPPORTED BY SCIENCE

What are acquired characteristics

A modification or change in an organ or tissue that is due to use, disuse, or environmental effects during an organisms lifetime

What are some examples of acquired characteristics

calluses, pierced ears, muscles from exercise

What is natural selection

organisms that are suited to their environment are more likely to survive and pass their genes onto their offspring 

what is the theory of natural selection based on

• variation exists in populations

• more offspring are born than can possibly survive

• organisms better suited to environment survive in greater numbers than those that aren’t

• over time the population is dominated by the organisms that have better suited genes to the environment

In order for a new species to arrive there must be:

Variation

Isolation

selection and speciation

What are some mechanisms of evolution

Natural selection

genetic mutation

gene flow

genetic direct

What is a gene

a unit of hereditary which is transferred from a parent to offspring

What are heritable traits

genetic traits which are passed down from parent to offspring. these are determined by genotypes from parents

examples of heritable traits

eye colour, fur colour, height, skin colour