Science

Unit 5

Growth & Development

DNA

• DNA are the building blocks of life, they are made with amino acids – They have four bases:

• Adenine• Cytosine• Gnamine• Thymine• Uracil

• DNA pairing go like this:A-TC-G

• Structure of DNA: A – TT – AC – GG – CG – CA – TC – GG – C

Size (from biggest to smallest): Cell – Chromosome – Gene - DNA

SPLITTING DNA!

• A-T/C-G bonds are held together by weak chemical bonds.

• Two strands separate; free bases form a second strand.

• - Each DNA molecule is made of half old and half new DNA- Each half of the split DNA molecule is complete making two identical DNA molecules.

Unspecialised Cells

Animals

• Stems cells (embryos) –Zygote (fertilised egg)

Plants

• Meristem cells - Roots

Phototropism

• Is when a plant GROWS towards the light.

• Auxins are hormones which make the plants do this. Auxins grow in the shaded part of a stem tomake itgrow tothe light.

Sexual Reproduction

• Meiosis – production of sex cells (each cell that’s made under Meiosis has ½ of chromosomes).

• Gametes – Sex cells (sperm/egg)

• Sperm + Egg = Zygote -> feutus.

KEY WORDS – NOT TO BE MISTAKEN

• MEIOSIS – Production of sex cells (each made with ½ of chromosomes)

• MITOSIS – duplicates cells identically (each made has all chromosomes).

Regeneration

• Where stem cells are used to form lsot limbs –a creature which does this is a newt. Only simple creatures like newts can regenerate.

Spheres of the world.

Main spheres we need to know

• Atmosphere – the layers of gas which cover the world (oxygen, Helium, Hydrogen, Carbon dioxide).

• Lithosphere – The rigid outer layer of the earth, made up of the crust and part of the mantle just below it

• Biosphere – All living organisms on earth.

• Hydrosphere – All the water on Earth (the only incomplete sphere).

Carbon Cycle

What is in the air?

Nitrogen78%

Oxygen19%

Carbon Dioxide

2%

Noble Gases

1%

Proportions of Gases in the atmosphere

1’s and 2’s and 3’s

• Remember, names like Carbon MONoxide and Carbon DIoxide have different numbers of oxygen particles and we can tell this by the way it says “mono” or “di” –here are all the terms that will be used up to 6.

• Mono = 1

• Di = 2

• Tri = 3

• Tetra = 4

• Penta = 5

• Hexa = 6

BONDING

• Of course, you know that this unit will have bonding. Here are the bondings:

• Ionic = Metal + Non-Metal

• Covalent = Non-mental + Non-Metal

• Metallic = Metal + Metal

Covalent Bonding

• Or “happy sharey hippie non-mental” bonding as a teacher likes to put it. This type of bonding is between NON-METALS! A prime example of this is Hydrogen atoms bonding to make a full shell.

But how do I know what a full shell looks like?• It’s simple. Each shell has a fixed

number of electrons they can have on it. In the picture below, you can see how many electrons this atom has and how many can go on each shell.

• Rules: the first shell from the centre must only have 2 electrons, the next two have 8 electrons.

• Knowing how many electrons there are here will help you with the next slide.

More Covalent Bonding!

• We know from the previous slide that the atom there has 18 electrons (which gives it 3 full outer shells). A Chlorine atom only has 17 electrons, which means it only has 2 complete shells and an incomplete shell.

• But, we know that this is a Diatomic element (that means it travels in a pair). We know this because it bonds with another Chlorine atom to make a full outer shell for both atoms.

• This is what I mean: the two chlorine atoms use their 1 electron in the incomplete shell to bond to the other in complete shell and make a full outer shell with another (it does sound very complicated, but very easy).

Hydrosphere

• Covers 2/3 of the earth’s surface• Contains dissolved salts (salts = any

ionic compound). FACT: these salts originally came from the lithosphere.

• A solid salt is a lattace, that means it’s a very strong chemical structure. The picture is a profile view of a lattace. (very badly drawn, my apologies).

• Lattaces break down and dissoveso that the Ions can move; they can also set up currents.

Lithosphere

• Cannot conduct as Ions.

• The solution is a mixture of Chrome alum (coloured) and magnesium sulphate (colourless).The chrome Alum crystals appeared first – this means that salt is less soluble in water than the solvant.The magnesium sulphate, higher solubility, and when it dissolves it’s saturated.

Graphite + Diamonds

• Graphite and Diamonds are allotropes of Carbon. Carbon wants 4 more electrons init’s outer shell so it needs to make 4 bonds.

• Diamond: All C-C bonds are same length.Properties of diamond1. Hard2. Covalent3. Carbon Only

• Graphite: 3 strong bonds connecting each layer. The electrons bonding them are free to move.Properties of Graphite:1. Covalent2. Long + Weak Bonds3. Carbon Only

EXTRACTING METALS!

• 2 METHODS!

• Burning with Carbon

• Key Terms: - Oxidation = addition of oxygen OR loss of electrons- Reduction = Loss of Oxygen OR Gain of electrons.

• The reaction below is Copper Oxide being heated with Carbon.

Carbon is Oxidised, Copper is Reduced.

Reactivity chart

• (really reactive)(cannot burn with Carbon, needs to use electrolysis)(reacts with water).- Lithium- Sodium- Calcium- Magnesium- Aluminium---------------------------------------------- Carbon (more reactive than below)- Zinc- Iron- Tin- Copper- Silver- Gold

• (Un reactive)(reacts with acids)(can burn with carbon to extract metals)

ELECTROLYSIS! (other method of extracting metals)

• Key Words: - Anode – Positive electrode (attracts negative Ions)- Cathode – Negative electrode (attracts positive Ions)- Electrolyte – The molten/dissolved Ionic compound.

• Basic explanation of how electrolysis works: you chuck in your Ionic compound into a beaker with two electrical poles at the top (Anode and Cathode) which is connected to an electrical current by wires; you turn the current on which makes the Anode and Cathode attract what they are meant to, which extracts/reduces metals from compounds.

• In the picture below, it shows you some solution of Sodium Chloride in a beaker which is about to be electrified. You see the NaCl particles floating about. But when the current is introduced in the picture in the right, the Na Ions go to the Cathode because they have a positive charge, where as the Cl Ions go to the Anode because they have a negative Charge.

Metallic Bonding

• This is a bond of Li (Lithium). • Metals are strong! They’re held together because the

nuclei are attracted to the whole sea of delocalised electrons. (Nuclei – more than one nucleus)

Outer Electrons are released into a delocalised (not belonging to one particular nucleus) sea of charge .

Electrical Circuits

These are only in note form, sorry.

Electrical Circuits

• The job of an electric circuit is to transfer energy to a place where it is needed.

• The lamp is an electrical device – it has resistance. It opposes the current.

Basic Ideas

• Electric current is when electrons start to flow around a circuit. We use an AMMETER to measure it and it is measured in AMPS.

• Potential difference (also called the VOLTAGE) is how big the push on the electrons is.

Equation

• I = Amps

• V = Voltage

Circuit = Key Symbols

• Bulb

• Volt Meter

• Ammeter

• Variable/Resistor

• LDR

Different types of circuits

Series Circuit

• Voltage gets shared between resistors

• Not useful

• Current = sameVoltage = Shared

Parallel Circuit

• Voltage is the same across each bulb

• Current = SplitsVoltage = same.

That’s It!

• GOOD LUCK!