Year 10 Science
Christmas Exam
Revision Notes - Cells
Cells
Animal v Plant Cells
Animal and Plant cells all have at least
a Nucleus, Cell Membrane and Cytoplasm.
Plant cells can have 3 extra organelles that Animal cells do not have; Vacuole, Cell Wall and Chloroplasts.
Cell Specialisation
Cells have particular shapes and parts to help them do their job in the Animal or Plant.
A root hair cell is a specialised cell found in the roots of plants. The cell is long and has a large surface area to help and absorb water and nutrients and from the soil.
Plants and Photosynthesis
Photosynthesis is a chemical reaction that takes place in the chlorophyll of plant leaves. It produces glucose and oxygen using carbon dioxide and water, with sunlight.
Without photosynthesis, we would not be able to make energy from respiration to keep us alive.
Plants convert the glucose made during photosynthesis into starch.
Iodine is an orange/brown chemical that changes blue/black in the presence of starch.
Testing a Leaf for Starch
Leaf is boiled in water to break down the leaf cells.
Boiled in alcohol to remove the green chlorophyll.
Leaf is then washed in water to soften it.
Iodine is added to the leaf.
If starch is present, the leaf will turn blue/black.
Revision Notes - DNA, Genes, Chromosomes, Nucleus and the Cell
Genes are found on Chromosomes and these contain instructions for inheritance such as eye-colour, hair colour, height etc. Each Gene contains strands of smaller DNA in a spiral Double Helix shape. Chromosomes are packed into the Nucleus of the Cell.
Continuous Variation involves a trait that can be measured; Height, Weight, Foot size, hand size. The Graph is usually ‘Bell Shaped’.
Discontinuous Variation involves a trait that can not be measured; Eye colour, ability to roll tongue, blood group.
Revision Notes - Environment & Classification
Animals and plants rely on each other survival.
Plants use light energy from the Sun to produce food by Photosynthesis – Plants are Producers
Animals eat plants for food. Other animals can eat these animals for food too. Animals are Consumers.
This transfer of chemical energy from plants to animals is called the food chain.
Revision Notes - Food Web
A large, varied environment will have many plants and many animals feeding on each other, this is called a food web.
In this food web the plants are the trees and grass.
Some plants are eaten by more than one animal.
Some of these animals are eaten by more than one other animal.
A food web is just lots of food chains put together.
In this food web if population of Mice die off, the Eagles will eat more Snakes and Frogs.
Revision Notes - Respiration
Respiration is a chemical reaction that takes place inside cells to provide the energy to keep them alive and carry out their functions. It uses Glucose (Sugar) from food eaten and Oxygen from the air breathed in. There are two types of respiration: Aerobic Respiration (with Oxygen) and Anaerobic Respiration (without Oxygen).
Aerobic Respiration – This type of respiration requires Oxygen. It produces lots of Energy.
Revision Notes - Solids, Liquid & Gases
All matter is made from very small particles (atoms). The particles are arranged in such as way that they can form Solid, Liquid or Gas materials. These are the 3 States of Matter:
Revision Notes - Elements, Compounds & Mixtures
All substances are made from Atoms.
Any two or more atoms joined together form a Molecule.
If the atoms are all the same it is an Element.
If there are two or more different Atoms in the Molecule it is a Compound. The Element Sodium (Na) chemically joins with Chlorine (Cl) to for Sodium Chloride (NaCl)
Revision Notes - Separating Techniques
Substances that are mixed together can be easily separated a number of separating techniques based on the properties of the substances:
Separating by Filtration
Used to separate an insoluble solid from a liquid. Eg Sand from Water. The residue (sand) is collected by the filter paper and the filtrate (liquid) is collected in the flask.
Separating by Evaporation
Used to separate a liquid from a soluble solid. Eg Water from Salt. The water is heated and evaporated into the surroundings, leaving the salt behind in the evaporating dish.
Chromatography
Used to separate a mixture of soluble Inks/Dyes. The ink gets drawn up through the chromatography paper. Ink that is most soluble in the water will move the furthest up the paper. A pencil origin line is used as pencil will not dissolve in water.
Separating using a Separating Funnel
Used to separate two immiscible liquids. Eg Oil and water. Oil is less dense than water and floats on the water. The tap on funnel is opened and water drained off and collected in a beaker.
Revision Notes - Solutes, Solvents and Solutions
One property of salt is that it is dissolves in water – it is Soluble.
It is said to be a Solute. Other solutes include sugar or a bath bomb as they also dissolve into water and form a Solution.
Revision Notes - Distillation
Used to separate a mixture of soluble solid and a liquid. However, the liquid can be kept and not lost to the surroundings. Eg. Separating water from salty sea water. First the water is evaporated as steam by heating it, leaving the salt behind, then it is condensed and cooled back down into liquid water.
Revision Notes - Rusting
Rusting
Most metals corrode, but when Iron corrodes it is called Rusting.
Both Oxygen and Water are needed for Iron to rust.
Boiled water removes oxygen. Oil prevents air re-entering water.
Calcium Chloride removes moisture (water) from the air.
The chemical name for rust Hydrated Iron Oxide.
Chemical Equation for Rusting
Ways to Prevent Rusting
Revision Notes - Acid & Alkalis
Acids and alkalis are corrosive. Acids and alkalis are chemical opposites.
Indicators can be used to show which substances are Acids and which things are Alkalis, or even Neutral.
Universal Indicator is an indicator that shows how strong or weak an acid or alkalis is, or if the chemical is Neutral.
The colour change is matched to the pH Scale. There are 14 different numbers and colours on the pH Scale.
Acids have a pH between 0-6
Neutrals are exactly 7
Alkalis have a pH between 8-14
Neutralisation
If two equal volumes and concentrations of Acid and Alkali are reacted it will produce a Neutral Solution made from Salt and Water.
This is useful in every-day life. A sting can be neutralised, cure indigestion or in farming:
· Bee Sting is Acidic and can be neutralised by Alkaline Baking Power.
· Lime is also Alkaline and is spread on soil that is too Acidic by farmers.
Hazard Symbols
Hazard Symbols are used to quickly identify dangerous Chemicals in the lab. They are easily identifiable and have universally understood pictures, especially if they are used for a concentrated Acid or Alkali:
Weak Acids or Alkalis with have a Caution (Health Hazard) symbol !
Stronger more concentrated Acid or Alkalis will have a Corrosive symbol.
Revision Notes - Reactivity Series
Metals can be ranked in order of reactivity, by reacting them with Air, Water or Acid.
Any metal above the (non-metal) hydrogen in the reactivity series will react with water and acids.
Metals below hydrogen like gold and silver are found in their pure form in the earth because they don’t react with water in the ground.
Metals and Water
Potassium, Sodium, Lithium react very quickly with
Water and are stored in oil to keep dry and away from air.
Potassium burns vigorously with a Lilac flame in water. Sodium with an Orange flame.
They both move around surface of water, melt, form a silvery ball and disappear.
When metals react with water they form metal hydroxide and give off hydrogen gas.
Sodium + Water → Sodium Hydroxide + Hydrogen
Safety and Alkali Metals
Alkali metals; Lithium, Sodium and Potassium need to be stored and used safely.
They are store in oil to prevent them from reacting with Oxygen and moisture (water) in the air.
Tweezers are used to hold them in case they react with moisture on the skin.
A safety screen is used when reacting them with water.
Goggles must always be worn
Metals and Acid
When metals react with acids they form metal salts and give of hydrogen gas.
Alkali metals must never be reacted with acids, as it is too dangerous.
Revision Notes - Energy
Energy is needed to get work done.
The unit of energy is the Joule. 1000J = 1kJ
There are many different types of energy.
Law of Conservation - Energy cannot be created or destroyed. Energy can only be transferred from one form to another. A light bulb transfers Electrical energy to Light energy and Heat (thermal) energy.
Energy is always lost when transfers take place. It is
usually lost as heat energy.
For every 100J of Electrical Energy that goes into a light bulb only 75J may be given out as Useful Light Energy . 25J is Wasted as Heat Energy. But the total energy out (100J) is the same as the 100J of electrical energy going into the bulb.
Measuring Food Energy
Chemical energy stored in food can be released by burning the food. Energy stored in two foods can be compared by:
1. Pouring the same volume of water into a boiling tube.
2. Measure the water temperature before burning food.
3. Burn the same mass of food under the boiling tube.
4. Completely burn food.
5. Measure water temperature after burning food.
Revision Notes - Energy Resources
Renewable Energy can be used again and will not run out. They include:
· Bio-fuels
· Wind
· Hydroelectric
· Tidal
· Geothermal
· Solar
· Water Waves
Non-renewable Energy cannot be used again and will run out, including: Fossil Fuels and Nuclear.
Revision Notes - Electricity
Electric current is the flow of electrons around a circuit.
Electrical Circuit symbols are a simple way of showing components in a circuit:
Conductors and Insulators
· Conductor is any material that conducts the flow of electrical current
· Insulator is any material that does not conduct the flow of electrical current
Series Circuit
A Series Circuit has components connect one after the other. Current can only flow along one path. If one component is off / does not work – all components do not work.
Parallel Circuit
A Parallel Circuit has components connect so that the current can flow along more than one path. Components can work independently
Revision Notes - Heat Transfer
There are 3 main ways in which heat is transferred:
Conduction – Transfer of heat through solids. Particles vibrate and pass on vibrations from particle to particle. Metals are the best conductors of heat. Plastic and Wood are poor conductors.
Convection – Transfer of heat through gas and liquids. Particles rise up as they become less dense. Water in a kettle.
Radiation – Transfer of heat by waves of energy. Can transfer through solids, liquids, gases and the vacuum of space. Eg Sun radiates heat.
Heat Insulators
Any material that is poor at transferring heat is an insulator. Materials that trap air are good insulators:
· Wool
· Feather
· Foam
Forces
Forces can affect objects in different ways by:
· Speeding them up / slowing them down
· Changing direction
· Change Shape
Forces are measured in the unit Newtons.
Balanced and Unbalanced Forces
If the forces acting on an object are equal, then the forces are said to be Balanced. The resultant force is 0N.
If the forces acting on an object are not equal then the object is said to be Unbalanced. The resultant force is not 0N.
Speed
The speed of an object is the distance it travels per unit time
For objects that are moving with a constant speed, use the equation below to calculate the speed:
Speed is measured in metres per second (m/s)
Distance travelled is measured in metres (m)
Time taken is measured in seconds (s)
Healthy Body
Smoking
Smoking causes chronic obstructive lung disease (COPD), coronary heart disease and increased risks of several different types of cancer, including lung cancer
Chemicals in cigarettes include:
Tar - a carcinogen (a substance that causes cancer)
Nicotine - an addictive substance which also narrows blood vessels
Carbon monoxide - reduces the oxygen-carrying capacity of the blood
Food Tests
We need a balanced diet of different food types that will provide the body with different nutrients and have different uses within the body:
