science gcse core, additional and triple powerpoints

1. C5 Chemicals of the Natural Environment Route map Over the next 12 lessons you will study : Friday 21 October 2011 C1.1 Chemicals in four spheres C1.2 Chemicals of the atmosphere C1.3 Chemicals of the hydrosphere C1.4 Chemicals of the lithosphere End of module test C1.5 Silicates of the lithosphere C1.6 Chemicals of the biosphere C1.7 Human Impacts on the environment C1.8 Metals from the lithosphere C1.9 Metals from the lithosphere (Part 2) C1.10 Metals from the lithosphere (Part 3) C1.11 Structure and bonding in metals C1.12 The life cycle of metals

3. Extension questions: 1: Name one thing from each sphere that you use every day (lithosphere, hydrosphere, atmosphere and biosphere) ? 2: What are the three most common elements in the hydrosphere ? 3: Which two spheres are involved in photosynthesis ? 4: Water is found mainly in the hydrosphere but where would it be found in the other three spheres ? 5: Where sphere to we extract rock ore like iron ore ? Know this: a: Know that oxygen is the most abundant element in the lithosphere but not in the atmosphere. b: Know that the elements are moving between the spheres all the time, being constantly reused and recycled. Friday 21 October 2011 Introduction: The Earth can be split into many spheres that surround it. The Lithosphere is made up by the mantle and the crust. The hydrosphere is the seas and oceans that sit upon the crust. The atmosphere is the gaseous layer than surrounds the Earth and keeps it warm and protected from electromagnetic radiation. The biosphere is all the living things that can live within the other spheres. These spheres are constantly interacting with each other and molecules and elements are moving between them. C5.1 Chemicals in four spheres

4. C5.1 a Look at the photograph and information and answer all the questions: Which part of the Earth’s crust is mineral rich and supports plant life ? What happens to the age of rocks as you travel from the surface of the crust to the crust upper mantle boundary? The lithosphere which is up to 100 km thick, includes the continental crust. This is the relatively cool and rigid part of the Earth’s structure. The Asthenosphere is the middle part of the mantle and has a consistency of hot plastic. The Mesosphere is the bottom part of the mantle, is higher in temperature than the lithosphere and is more rigid due to an increase in pressure. What supports life is the very top of the crust and its soil. The Earth’s crust The hydrosphere does not cover the whole of the Earth’s surface. Do you think it is still right to call it a sphere ? Explain ! Key concepts

5. Key concepts Look at the photograph and information and answer all the questions: Although aluminium is more abundant than iron which is used to make steel and stainless steel, aluminium is more expensive…explain why ? The wet mass of an average human is 70 kg, the dry mass (after cremation) is about 600 grams.. what's missing ? The abundance of elements in the four sphere changes. In the lithosphere, the most abundant element is oxygen lock in compounds like silicon dioxide and other oxides. In animal flesh (including humans) the most abundant element is also oxygen. This is largely in the form of water. Carbon is the second most abundant element in animals as it forms the backbone of large biological molecules like proteins, lipids and carbohydrates. C5.1 b Key elements found in the lithosphere and human tissue

6. Key concepts Look at the photograph and information and answer all the questions: Chemicals like carbon dioxide (CO 2 ) and water (H 2 O) do not always stay in one of the four sphere. The are able to move between spheres. Think of water in liquid in the rivers and seas as part of the hydrosphere. When water evaporates it is now part of the atmosphere. Found in the biomass of plants and animals it becomes part of the biosphere. Explain how a) carbon in the form of CO2 us removed form he atmosphere into the cells of plants ? What drives the water cycle across the globe ? Give three other elements or compounds that flow between different speheres ? C5.1 c CO 2 (g) H 2 O (g) H 2 O (l) Molecules flowing in and out of spheres C (s)

7. Plenary Lesson summary: lithosphere atmosphere hydrosphere biosphere Friday 21 October 2011 The lithosphere, hydrosphere and atmosphere are the source of all our raw materials like metal ores used to extract metal, soil nutrients to support plant growth, the air that we breathe, oil reserves to make plastic fuels lubricants and dyes and gold and other precious mineral deposits. How Science Works: Research into the Earth’s atmosphere including the composition of different gases in atmosphere. Look at how we are changing the composition of our atmosphere by burning fossil fuels. Preparing for the next lesson: The Earth is made of many spheres. The ________ is made of rock and contains many metals. The ________ is made up of oceans and seas but doesn’t quite cover the Earth. All life makes up the _____________. The Earth is surrounded by the _________ which keeps the planet warm C5.1 Decide whether the following statements are true or false : False True 3: Most biological compounds are based on the element silicon ? False True 2: The Earths core is split into an inner and outer section ? False True 1: Nitrogen is the most common element found in the atmosphere ?

9. Chemicals of the atmosphere Extension questions: 1: If you had 100 litres of atmospheric air, estimate the volume of a) nitrogen b) oxygen and c) argon ? 2: If you compared the water content of air collected in a desert and air collect in a tropical jungle how would it differ ? 3: Hydrogen and Chlorine have 1 and 7 electrons respectively in their outer shell. How many covalent bonds can they form ? 4: Draw a diagram showing the covalent bonding in HCl and CH 4 5: Which species uses carbon dioxide ? Know this: a: Know the composition of gases in our atmosphere. b: Know the nature of the bonding and attraction in and between gas molecules found in our atmosphere. Friday 21 October 2011 Introduction: Due to the Earths gravity, the gases in our atmosphere are kept just above the Earths crust. The composition of these gases is 78% nitrogen, 21% oxygen, 1% argon and 0.03% carbon dioxide. Between this mixture of gaseous compounds and elements are very weak forces of attraction. They are not very strong though and the molecules do not ‘stick’ together for very long. Between atoms in the same compounds are covalent bonds that hold individual atoms together (e.g. CO 2 O 2 H 2 O) To break these bonds require lots of energy because they share electrons and the attraction of the electrons to the nucleus is very large. C5.2

10. Look at the photograph and information and answer all the questions: Our atmosphere can sustain life at a height of about 10 km above sea level. It is a mixture of billions of tonnes of different gases. Our atmosphere insulates us and protect us against UV radiation. The present composition of the atmosphere is 78% nitrogen, 20% oxygen, and 1% other gases including carbon dioxide and the Noble gases (Neon, Argon, Krypton & Xenon). Which gas do we exchange in our lungs and use to respire glucose producing water and carbon dioxide ? Describe how water content would change in a sample of air taken form a tropical rain forest and a desert in the sub Sahara ? Are we adding or removing carbon dioxide to our atmosphere by burning fossil fuels like petrol and diesel ? key concepts Oxygen (O 2 ) Nitrogen (N 2 ) Water (H 2 O) Ozone (O 3 ) dioxide (CO 2 ) Carbon Gases found in the atmosphere C5.2 a

11. Look at the photograph and information and answer all the questions: Emissions form car exhausts contain toxic gases. These gases are breathed in and transported to all the body's major organs. These pollutants include, carbon monoxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, dinitrogen oxide, sulphur dioxide, low level ozone, and particulates. The most obvious health impact of car emissions is on the respiratory system. Both nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) are toxic even at low levels causing lung damage and higher blood pressure...explain what effects these gases may have on a) an asthma sufferer and b) some with cardiovascular problems ? Explain why regular vehicle emission testing helps maintain good air quality in cities across the country ? What effect will sulphur dioxide (SO 2 ) have on the environment ? key concepts Ozone (O 3 ) low level Sulphur dioxide (SO 2 ) Nitrogen monoxide (NO) Nitrogen dioxide (NO 2 ) Dinitrogen oxide (N 2 O) dioxide (CO 2 ) Carbon monoxide (CO) Carbon Particulates C5.2 b

12. Key concepts Look at the photograph and information and answer all the questions: Draw (just like CO2) a ball and stick model of a) H2 b) H2O and c) N2 ? The atoms in any molecule picture above (CO 2 , O 2 , H 2 , N 2 and H 2 ) are held together by electrostatic attraction between two nucleis and a shared pair of electrons. This is a single covalent bond. This type of bond is strong and the word covalent means co ‘together’ and valent ‘strength. The number of covalent bond an element can make depends on the number of electrons. Carbon can form four single bonds for example. Carbon dioxide Oxygen Covalent molecules found in air Nitrogen Hydrogen Water C5.2 c carbon dioxide In the carbon dioxide molecule, the carbon forms two bonds with each oxygen atom. These double bonds between carbon and oxygen do you think they are stronger or weaker than single covalent bonds ?

13. Plenary Lesson summary: Oxygen covalent weak mixture Friday 21 October 2011 The term "covalence" in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of the American Chemical Society article entitled "The Arrangement of Electrons in Atoms and Molecules". Walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond, specifically that of molecular hydrogen, in 1927. How Science Works: Find out what is meant by the term salt. It isn’t just the stuff you put on your chips! Preparing for the next lesson: The atmosphere is a ________ of gases such as hydrogen and _________. Between these gases there are _________ attractive forces that aren’t strong enough to hold them together. Between atoms though are ________ bonds which are much stronger. C5.2 Decide whether the following statements are true or false : False True 3: Carbon dioxide contains two double bonds. False True 2: The atmosphere is held in place by the ozone layer False True 1: Covalent bonds take place between metal atoms

15. Extension questions: 1: Show the three states of water and what is the melting and boiling points of water ? 2: Draw a table to show properties of water that are common with other molecules in one column and another of unusual properties ? 3: Draw a diagram to show how the water cycle has caused the sea to become salty ? 4: Does pure water conduct electricity ? Why or why not ? 5: Explain why for life to exist the presence of water is essential ? Know this: a: Know that water has the formula H 2 O is a covalent molecule and is called the universal solvent. b: Known that rivers are slightly salty as they carry dissolved salts down into the seas and ocean where they have accumulated over time. Friday 21 October 2011 Introduction: Water with the formula H 2 O is one of the most important chemicals on the Earth. This is because of it’s very unique properties. Normally when a liquid solidifies it contracts but water actually expands to make ice. The molecules are also dipolar meaning they have a negative charge at one end and a positive charge at another. This means that they can separate ionic compounds (and are therefore good at dissolving them). When rain lands on the lithosphere, ionic compounds are then dissolved and carried by rivers out to sea. Over millions of years this has made the seas and oceans salty. Chemicals in the hydrosphere C5.3

16. Look at the photograph and information and answer all the questions: Gases, liquids and solids are all made up of particles, but the behaviours of these particles differ in the three phases. Particles in a gas are well separated with no regular arrangement moving freely at high speeds, in a liquid particles are close together with no regular arrangement sliding about one another and in a solid particles are tightly packed, usually in a regular pattern vibrating around a fixed point. Explain what happens when a) ice melts and b) water freezes 9think about the water molecules and density? On Earth water exits mostly in the liquid state, where would you find water in the a) solid and b) gaseous state ? Give three ways water has shaped the lithosphere, for example glacier ice eroding huge valleys over time? Solid Liquid Gas a b c d a melting b freezing c evaporation d condensation Sates of matter C5.3 a Key concepts

17. Key concepts Look at the photograph and information and answer all the questions: Water is a very important biological solvent without which life would not exist: Water is composed of two hydrogen atoms and one oxygen atom and has the formula H 2 O. Water itself is a polar solvent because it has charged areas. Oxygen has a slight negative charge and the hydrogen atoms have a slight positive charge. What is the % of water in a hydrated human body and what hormone controls the amount of water excreted via the kidneys What are the melting and boiling points of water and what happens to water molecules as they change state from liquid to gas ? Explain in two to three sentences why life cannot exist without the presence of water ? C5.3 b

18. Key concepts C5.3 c Look at the photograph and information and answer all the questions: The positively charged hydrogen atoms are attracted to the negatively charged oxygen atom of a nearby water molecule. This lining up of the O-H atoms is called hydrogen bonding. These forces of attraction are relatively strong and determine the higher than expected melting and boiling points of H 2 O. The polar nature of the water molecule also solvate ions like sodium (Na + ) and chloride (Cl - ) Looking at the diagram above left, explain how water molecules solvate or dissolve the sodium ion ? Looking at the diagram above right, explain how water molecules solvate or dissolve the chloride ion ? Water as a polar solvent Na + Cl -

19. Plenary Lesson summary: salts charge weathering H 2 O Friday 21 October 2011 Canyons are formed by a process of long-time erosion by rain and rivers. The most famous canyon is the Grand Canyon in Arizona in the USA. It has an average depth of one mile and a volume of 4.17 trillion cubic metres. That is big!! How Science Works: Research into chemicals of the lithosphere particularly ionic compounds and minerals like calcite, pyrite and haematite. Preparing for the next lesson: The chemical formula for water is ________. Water has a slight positive _______ at one end and a negative one at the other. This property allows it to dissolve charged ionic compounds and when ____________ takes place, ________ dissolve in the water. C5.3 Decide whether the following statements are true or false : False True 3: Water dissolves compounds that aren’t ionic ? False True 2: The name for salt you put on food is potassium chloride ? False True 1: Water molecules contain two covalent bonds ?

21. Extension questions: 1: Write a sentence describing the differences between rock, mineral and lithosphere ? 2: What is the most abundant and second most abundant metals in the lithosphere…give a use for each metal ? 3: What is the most abundant non-metal ? 4: Name the elements found in the following minerals a) Haematite Fe 2 O 3 , b) Calcite CaCO 3 c) Pyrite FeS 2 and d) Rock salt NaCl ? 5: Draw a thee dimensional crystal of sodium chloride containing 9 sodium ions and 9 chloride ions ? Know this: a: Know that rocks are formed from minerals and that minerals are made up of simple or complex chemicals Know that sodium chloride, sodium (Na + ) has the positive charge and chlorine (Cl - ) has the negative charge. Friday 21 October 2011 Introduction: We live on the crust of the lithosphere. There are many different types of rock and different sizes; from pebbles to cliffs. All rocks are made of minerals; they may be one mineral or a composition of many. Sandstone is mostly silicon dioxide whereas granite is a mix of many different minerals compacted together. Minerals are naturally occurring chemicals that may be found as elements such as gold or in compounds such as iron oxide or silicon dioxide. Many of the minerals are ionic compounds like sodium chloride. As the crystal of sodium chloride form, ions are packed closely together and are held there by the opposite charges of the ions. This is ionic bonding which is very strong due to the strong attraction of the ionic charges. Chemicals of the lithosphere C5.4

22. Key concepts Look at the photograph and information and answer all the questions: Name the elements found in a) iron pyrite FeS 2 , Calcite (CaCO 3 ) and Haematite (Fe2O 3 ) ? Metals are extracted from minerals ore, name three metals and their ores ? The rocks you see around you - the mountains, canyons & riverbeds, are all made of minerals. A rock is made up of 2 or more minerals. A mineral is composed of the same substance throughout. Minerals are made of chemicals - either a single chemical or a combination of chemicals. There are about 3000 different minerals in the world. These 3000 minerals can be sorted into just 8 groups. C5.4 a Minerals found in rocks Iron pyrite Calcite Haematite FeS 2 CaCO 3 FeO 3

23. Key concepts Look at the photograph and information and answer all the questions: Give three uses of salt, for example it is used a a raw material in the extraction of chlorine ? Name three other ionic compounds other than salt, sodium chloride ? Sea water contains lots of dissolved ionic compounds like sodium chloride. When the water evaporates, the dissolved ionic compound crystallise. This is how common rock slat (halite is formed) All minerals formed in this way are called evapourites. In Cheshire we have huge deposits of rock salt that were formed about 200 million years ago. They have since be covered by other sedimentary rocks. C5.4 b Formation of evapourites Na + Cl -

24. Key concepts Look at the photograph and information and answer all the questions: Ions of atoms build crystals. The structure extends itself in all directions, giving the crystal a regular arrangement of ions called a lattice. For sodium chloride, the ions arrange themselves alternatively in all three dimensions. This gives sodium chloride crystals a cubic shape. All ionic solids have similar ionic structures to sodium chloride. Write the formulae of the following ionic compounds a) magnesium chloride b) aluminium oxide c) calcium carbonate and d) copper sulphate ? Explain (looking at the picture opposite) the arrangement of the sodium and chloride ions in sodium chloride ? Which of the following compounds contain molecules and which contain ions a) Octane b) copper oxide c) water d) hydrochloric acid and e) calcium chloride ? C5.4 c Ionic bonding in sodium chloride

25. Key concepts Look at the photograph and information and answer all the questions: Sea water contains lots of dissolved ionic compounds like sodium chloride. When the water evaporates, the dissolved ionic compound crystallise. This is how common rock slat (halite is formed) All minerals formed in this way are called evapourites. In Cheshire we have huge deposits of rock salt that were formed about 200 million years ago. They have since be covered by other sedimentary rocks. Explain what happens to the single electron placed in the outer orbital of the sodium atoms as sodium chloride is formed ? Draw using the dot and cross diagram (outer shell only) the product sodium chloride showing the correct charge on the ions of each atom ? Do a similar dot and cross diagram to show a) the transfer of electrons between magnesium and chlorine and b) the products of this reaction ? Na (s) + Cl 2 (g) 2NaCl (s) C5.4 d Ionic bonding in sodium chloride 11 23 Na 17 35.5 Cl

26. Plenary Lesson summary: Ionic minerals granite lithosphere Friday 21 October 2011 Evaporation is an essential part of the water cycle. Solar energy drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water. Over time the process of water evaporating form shallow seas created vast deposits of rock salt. In Cheshire this is mine to extract brine and salt which is used to preserve food and in the extraction of chlorine. How Science Works: Research about the chemical and physical properties of silicon dioxide in quartz. Preparing for the next lesson: ________ bonds are very strong as they contain two charged ions that attract to each other. Within the _________ there are many rocks that contain different _________. __________ is one example that contains quartz, feldspar and mica. C5.4 Decide whether the following statements are true or false : False True 3: Ionic bonds are very strong and requires large amount of energy to break ? False True 2: Granite is made of two minerals mixed together ? False True 1: The structure of ionic crystal is called a large ionic structure ?

28. Extension questions: 1: Give three possible uses of silicon dioxide as an abrasive ? 2: What is an insulator and why can it be used in electrical devices ? 3: Why is sandstone suitable for buildings, but not for making kitchen worktops. Why might granite be better ? 4: Explain why silicon dioxide not soluble in water ? 5: Explain quartz hardness and high melting point based on its structure ? Know this: a: Know the physical and chemical properties of silicon dioxide. b; Know that quartz is used in communications c: Know that amethysts, form of quartz is a valuable gemstone. Friday 21 October 2011 Introduction: The mineral silica contains the compound silicon dioxide. The most common crystallised form of this is quartz. When silicon bonds with oxygen, four bonds are formed by silicon and two by oxygen. This creates a giant covalent structure. The covalent bonds between silicon and oxygen are very strong and therefore the giant covalent structure is too. This means that silicon dioxide has some very important properties including being very hard, having a very hard melting point, its’ insoluble in water and acts as an electrical insulator. Silica and silicates of the lithosphere C5.5

29. Key concepts C5.5 a Look at the photograph and information and answer all the questions: Look at the bonding it silicon dioxide show above, explain how the oxygen and atoms are arranged ? Quartz is a naturally occurring silicate mineral composed of silicon dioxide (SiO 2 ). Its hardness is 7 on the Mohs scale and it is in the trigonal crystal system. Quartz can be found in all three rock types, igneous, metamorphic, and sedimentary. Quartz has a white streak, but specimens can be appear coloured by impurities or exposure to heat or radiation to hues of white, pink, red, yellow, blue & green, What other substance is known for its incredible hardness and very high melting point and do you think this substance is also a giant covalent structure ?

30. Key concepts C5.5 b Look at the photograph and information and answer all the questions: Quartz has a meting point of 1610 o C why does this make it suitable as a lining for high temperature ovens ? Quartz is the most common mineral on the face of the Earth. Quartz is not the only mineral composed of SiO 2 . Quartz minerals are very stable and only under high temperatures and high pressures or both do they melt . The strength of quartz and its very high melting points makes it useful in industry, for example sandpaper uses quartz as the abrasive. It can also be used to line high temperature ovens. Physical properties Strong, rigid, giant covalent structure High melting point difficult to breakdown Will resist weathering and erosion by water and wind Use in sandpaper as an abrasive to clean wood and metal Used to line high temp ovens and pottery ovens Used in sandstone to build buildings Uses and applications Based on the giant covalent structure found in quartz, explain the following a) its hardness, and b) its insulating properties ?

31. Plenary Lesson summary: oxygen dioxide hard covalent Friday 21 October 2011 Quartz crystals have piezoelectric properties; they develop an electric potential upon the application of mechanical stress. This means that they are used in wave machines that transform the up swell of the seas and oceans into an electrical current. They are also used in lighters to create a spark to light the gas fuel. How Science Works: Research about chemicals of the biosphere including molecules like glucose, carbohydrates, proteins, lipids and DNA. Preparing for the next lesson: Silicates are very common minerals and consist of silicon ________. They form giant __________ structures due to the bonds between silicon and __________. The properties of this structure such as being very __________ give it many possible uses. C5.5 Decide whether the following statements are true or false : False True 3: Silicon dioxide is used in electrical equipment as it conduct electricity well ? False True 2: Silicon dioxide is used to line extremely hot furnaces ? False True 1: Quartz is very expensive and rarely found in Earth’s crust ?

33. C5.6 Chemicals of the biosphere Extension questions: 1: List the seven vital nutrients to support life ? 2: In that list of seven nutrients only three provide the body with energy and the building blocks for other biological molecules, which three ? 3: What function do a) protein and b) lipid play in the body? 4: What element is common in nucleic acids but not in carbohydrates? 5: What are the four bases found in nucleic acids ? Know this: a: Know the nature of biological molecules found in living organisms. b: Know that DNA stands for deoxyribonucleic acid c: Know that long chain molecules made form monomers are called polymers. Friday 21 October 2011 Introduction: The element carbon is vital to all life and biological molecules in the biosphere would not exist without it. Carbon can form long chains with other carbon atoms as they form four strong covalent bonds. Proteins, carbohydrates, lipids and Nucleic acids all vital for life, contain carbon. Proteins are needed for your body to grow and are made up of long chains of amino acids. Carbohydrates are sugars that are needed for energy. Lipids are needed to make hormones, cell membranes and as long term energy stores. Nucleic acids are chemicals that carry genetic code.

34. Key concepts Look at the photograph and information and answer all the questions: Name three naturally occurring polymers (e.g. proteins) and three synthetic polymers (e.g. Nylon) ? Compare the different properties and roles of proteins and carbohydrates in the body ? The human body contains thousands of different biological molecules, each with a specific role. May of then biological molecules are polymers or long chain molecules with a carbon back bones Carbon can form these different molecules because of its unique ability to form four covalent bonds. These properties of carbon allows for an amazing variety of compounds all essential to life. C5.6 a Muscles fibres consist of proteins polymers Bones contain minerals built around a protein (collagen) Cells contain DNA built from thousands of nucleotides Hair is made from keratin protein Glycogen a polymer of glucose is stored in the liver Haemoglobin a protein rich in iron that carries oxygen

35. Key concepts Look at the photograph and information and answer all the questions: What role or roles do the following cell parts or cell organelles play in plant or animal cells a) mitochondria b) chloroplast and c) vacuole ? Name the three elements that make carbohydrates and what are their role in both plants and animals ? Cell organelles, like mitochondria and chloroplasts carry out important functions in plant and animal cells. The nucleus controls the activity of the cell by building new proteins including enzymes. It also contains DNA, the material of inheritance. Mitochondria found in both plant and animal cells respire glucose with oxygen releasing cellular energy, carbon dioxide and water. Chloroplasts found only in plant cells produce glucose and oxygen from carbon dioxide and water. Molecules in animal cells Molecules in plant cells C5.6 b Nucleus Nucleus Cytoplasm Cytoplasm Cell membrane Cell membrane Mitochondria Mitochondria Chloroplast Vacuole Cell wall

36. Assessment for learning...key concepts Look at the photograph and information and answer all the questions: Explain the difference between a) a gene and DNA and b) a chromosome and gene ? Explain why your chromosome stay in the cell nucleus ? We humans have 23 pairs of chromosomes making 46 in total that carry the many thousands of genes, in sequence, that determine the our characteristics. Each chromosome normally consists of one very long double strand (or molecule) of DNA, coiled and folded to produce a compact structure. DNA is made form just four different nucleotides: adenine, cytosine, guanine and thymine C5.6 c Name the elements that are present in DNA’s nucleic acids?

37. C5.6 Plenary Lesson summary: protein nucleic carbon amino acids Friday 21 October 2011 Did you know that much of your DNA is called ‘junk DNA’ as it does not have any purpose. Your cells cut out the junk when they are making proteins (structural or enzymes). Only certain genes are switched on or are active in the cell. How the cell does this and pick the right genes is still unclear. How Science Works: Research into what impact humans have on the four different spheres. Preparing for the next lesson: The biosphere contains many important chemicals such as carbohydrates and ___________ which are made of ___________. __________ acids such as DNA carry our genetic code. All these chemicals contain _____________. Decide whether the following statements are true or false : False True 3: Carbon can form four covalent bonds with other non metal atoms ? False True 2: You inherit you DNA form your mother and father ? False True 1: Proteins are made up of long chains of glucose monomers ?