physicd all

• Limits to the use of fossil fuels and global warming are critical problems for this century.
• The concept of energy became a key tool for understanding chemical reactions and biological systems.
• The concept of energy emerged in the 19th century to explain the work output of steam engines and then generalised to understand other heat engines.
• Physicists and engineers are working hard to identify ways to reduce our energy usage.
• Power can be calculated as energy transferred time, P = E/t, or as work done time, P = W/t.
• An energy transfer of 1 joule per second is equal to a power of 1 watt.
• The energy efficiency for any energy transfer can be calculated using the equation: efficiency = useful output energy transferred total input energy transferred.
• Ways of reducing unwanted energy transfers include lubrication and the use of thermal insulation.
• The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.
• Power is defined as the rate at which energy is transferred or the rate at which work is done.
• Change in thermal energy, ∆ E, is calculated by the equation: ∆ E = m c ∆ θ.
• Efficiency may also be calculated using the equation: efficiency = useful power output total power input.
• The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.
• Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.
• The rate of cooling of a building is affected by the thickness and thermal conductivity of its walls.
• The temperature of the gas is related to the average kinetic energy of the molecules.
• The specific latent heat of vaporisation is the amount of energy required to change the state of one kilogram of a substance from liquid to vapour.
• Heating changes the energy stored within the system by increasing the energy of the particles that make up the system.
• Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.
• The specific latent heat of a substance is the amount of energy required to change the state of one kilogram of the substance with no change in temperature.
• The energy needed for a substance to change state is called latent heat.
• When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.
• The energy for a change of state is calculated by the equation: energy for a change of state = mass × specific latent heat.
• The specific latent heat of fusion is the amount of energy required to change the state of one kilogram of a substance from solid to liquid.
• Changes of state are physical changes which differ from chemical changes because the material recovers its original properties if the change is reversed.
• Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.
• The molecules of a gas are in constant random motion.
• The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.
• Working scientifically is the sum of all the activities that scientists do.
• The way scientific ideas flow through the specification supports the development of knowledge and understanding in science through opportunities for working scientifically.
• Working scientifically involves investigating, observing, experimenting or testing out ideas and thinking about them.
• Use of models in scientific thinking involves recognising/drawing/interpreting diagrams, translating from data to a representation with a model, using models in explanations, or matching features of a model to the data from experiments or observations that the model describes or explains.
• Working scientifically can be assessed through the development of scientific thinking, use of models, appreciation of the power and limitations of science, everyday and technological applications of science, evaluation of associated personal, social, economic and environmental implications, and decision making based on the evaluation of evidence and arguments.
• Evaluation of associated personal, social, economic and environmental implications involves describing and explaining specified examples of the technological applications of science, describing and evaluating methods that can be used to tackle problems caused by human impacts on the environment, and evaluating risks both in practical science and the wider societal context, including perception of risk in relation to data and consequences.
• Science is a set of ideas about the material world.
• Use of scientific theories and explanations to develop hypotheses involves suggesting a hypothesis to explain given observations or data.
• Development of scientific thinking involves understanding how scientific methods and theories develop over time, using a variety of models, appreciating the power and limitations of science, and considering any ethical issues which may arise.
• Communicating results to a range of audiences involves recognising the importance of peer review of results and of communicating results to a range of audiences.
• The specification encourages the development of knowledge and understanding in science through opportunities for working scientifically.
• The pressure at the surface of a fluid can be calculated using the equation: