science 4's

Homeostasis - B4

Explaining Motion -P4

Chemical Patterns - C4

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  • Created by: Ruth
  • Created on: 27-03-11 10:49

C4 - Chemical Patterns

the periodic table 

an element = 1 kind of atom the atoms have the same number of protons

group - verticle = number of electrons in the outer shell of atom

peroid - horizontal = number of shells in atom

atroms = no overall charge

nucleus = surroundes by electrons (negative) made up of protons (positive) + neutrons (no charge)

Spectroscopy

line spectrum =light emitted from flame of an element when heated 

lithium - red soduim - yellow potassuim - lilac

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electron configuration = how the electrons are arranged around the nucleus

first shell - up to two  shells after - up to 8

balanced equations 

total mass of products = total mass of reactants

no atoms are lost or made in a chemical reaction

Alkali Metals 

alkali metals - group 1 - 1 electron in outer shell

the reactivity of alkali metals increases down the group, this is because the outer shell gets further away from the nucleus and electrons are more easily lost

alkali metal + water = metal hydroxide + hydrogen

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Halogens - group 7 - 7 electrons in the outer shell.

they decrease down the the group, as the outer shell gets further from the nucleus and electrons are less easily gained. a more reactive halogen will displace a less reactive halogen.

at room temperature/pressure: chlorine = green gas. bromine = orange liquid. iodine = dark purple solid. 

Compounds

 ions = atoms that have gained or lost electrons, have an overall charge

ionic bonding = transfer of electrons between metal atoms an non metal atoms.

atom loses electrons - positive charged ion. atom gained - negative charged atom.

ionic compound - group 1 + group 7. from crystals as ions are arranged in regular lattice. when crystals melt/dissolve in water they conduct electricity

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speed - how fast an object is moving 

instantaneous speed - speed of an object at a particular point in time

Velocity - describes an objects speed and direction

the gradient of velocity-time graph = how quickly object increases in speed

steeper the slope - faster the speed is increasing

Forces - occurs when two objects interact with each other

Gravity - force of attraction between all masses

Air resistance - air tries to slow an object down

Reaction of the surface - object is pulled down on to the surface by gravity, surface pushes up on to the object with equal force.

Friction - the force that tries to stop two objects moving as they slide past.

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Resultant Force - effect of adding or subtracting forces

size of force arrow = size of force

Direction of force arrow = direction force is acting in 

force arrows are always drawn with the tail of the arrow touching the object

Momentum - measure of the motion of an object 

collisions - cause changes in momentum

if a change in momentum is spread out over a longer period of time, the resultant force will be smaller.

increasing time of impact - reduces force of impact 

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Energy 

kinetic energy - energy of object has because of its movement. depends on mass and velocity or object.

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