Science

• Topics to revise


  • Working scientifically
  • States of matter and particles
  • Variety of life
  • Forces
  • Mixtures and separation
• Working scientifically


  • Plan a scientific investigation
  • Draw a line graph and a bar graph
• Independent variable


  The one you change
• Dependent variable


  The one you measure
• Control variables


  Things you keep the same so they don't affect the result
• SLAPUK is a way to remember how to construct a graph
• Hazard


  Something that could cause harm to someone, damage to something, or adverse health effects
• Hazards


  • Concentrated acids are corrosive
• Hazard symbols


  Indicate the dangers associated with the substance and give information about how to work safely with it

  
• Common pieces of apparatus in a science lab

  • Beaker
  • Bunsen burner
  • Thermometer
  • Measuring cylinder
  • Pipette
• Variables


  Factors that can change and be measured
• Independent variable


  The variable that is being changed during the experiment
• Dependent variable


  The variable being tested or measured during the experiment
• Control variables


  Variables that must be kept the same so they don't affect the independent variable
• Knowing which variables to control is important when designing experiments to find out if a prediction is right or wrong
• Identifying control variables makes sure that only the independent variable affects the dependent variable, ensuring valid results
• Hypothesis


  An idea or question based on an observation that can be tested with an experiment
• Prediction


  A statement about what will happen in an experiment if the hypothesis is right
• Types of data


  • Continuous
  • Discrete
  • Categoric
• Continuous data


  Numeric data that can have any value within a range
• Discrete data


  Numeric data that can only have certain values
• Categoric data


  Data that are words
• Line graph


  Should be used when the independent and dependent variables are continuous
• Bar chart


  Should be used if the independent variable is categoric
• Pie chart


  Can be used for discrete or categoric data, often to show percentages
• The independent variable goes on the horizontal (x) axis and the dependent variable goes on the vertical (y) axis when drawing graphs and charts
• Conclusion


  Describes the relationship between variables, links findings back to the hypothesis, and explains findings using scientific knowledge
• If a numerical relationship between variables has been discovered, it should be included in the conclusion
• Things to evaluate when evaluating results

  • Outliers
  • Spread in the data
  • Enough results taken
• Things to evaluate when evaluating the method

  • Did it produce results that allow a conclusion to be reached?
  • Was it a valid test?
  • Could other apparatus have been used?
• Particle theory of matter


  A model that describes the arrangement, movement and energy of particles in a substance
• States of matter


  • Solid
  • Liquid
  • Gas
• Solids


  • Have a fixed shape and cannot flow, cannot be compressed
• Liquids


  • Flow and take the shape of their container, cannot be compressed
• Gases


  • Flow and completely fill their container, can be compressed
• Some substances can change directly from solid to gas without becoming a liquid in between, this is called sublimation
• Melting, evaporating and boiling


  Energy must be transferred, by heating, for these changes of state to happen
• The amount of energy needed to change state depends on the strength of the forces between the particles of a substance</b>
• Substances and their melting and boiling points

  • Sodium chloride (ionic): melting 801°C, boiling 1413°C
  • Water (small molecules): melting 0°C, boiling 100°C
  • Hydrogen (small molecules): melting -259°C, boiling -252°C
• Evaporation can take place below the boiling point of a substance