Grade 8 Science Unit 1: Mix and Flow of Matter
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Questions and Answers

What happens to the buoyant force when the density of a fluid decreases?

  • It remains constant
  • It increases
  • It decreases (correct)
  • It becomes zero
  • Why did each jar float at a different height in the experiment?

  • Because of the different viscosities of the substances
  • Because of the different densities of the substances (correct)
  • Because of the different compositions of the substances
  • Because of the different volumes of the substances
  • How would increasing the nozzle opening affect the rate of flow of the window washer's spray?

  • It would make the flow more turbulent
  • It would increase the rate of flow (correct)
  • It would decrease the rate of flow
  • It would have no effect on the rate of flow
  • How do snowshoes make it easier to walk over snow?

    <p>By spreading out the force over a larger area</p> Signup and view all the answers

    Why are wider, thicker tires used on mountain bikes or all-terrain vehicles?

    <p>Because they exert less pressure on the ground</p> Signup and view all the answers

    What is the correct unit of measurement for water pressure?

    <p>Pascals (Pa)</p> Signup and view all the answers

    What is the relationship between the density of a substance and its buoyancy in a fluid?

    <p>Density is inversely proportional to buoyancy</p> Signup and view all the answers

    How would lengthening the hoses affect the rate of flow of the window washer's spray?

    <p>It would decrease the rate of flow</p> Signup and view all the answers

    Why do objects with a higher density tend to sink in a fluid?

    <p>Because they are denser than the fluid</p> Signup and view all the answers

    What is the primary factor affecting the pressure of a fluid at a given depth?

    <p>The density of the fluid</p> Signup and view all the answers

    Study Notes

    Observing Fluid Flow

    • To observe a gas flowing, use its effect, as gases cannot be seen or heard.
    • Characteristics of fluids include their effect, hearing, seeing, and feeling.

    Properties of Substances

    • Properties of substances can be classified into two categories: physical properties and properties of behavior.
    • Physical properties include color, density, and crystal size.
    • Properties of behavior include whether a substance burns, rots, or explodes, and its reactivity.

    Chemical Properties

    • Chemical properties include reactivity, acidity, and solubility.
    • Chlorine is useful because of its reactivity.

    States of Matter

    • Substances can exist in different states, such as hydrated (with water) or anhydrous (without water).
    • Copper II Sulphate can be hydrated or anhydrous.

    Mixtures

    • A mixture is a combination of two or more substances that can be separated by physical means.
    • To determine if a substance is a mixture, look for the number of parts visible.
    • Mortar is a mixture of sand and cement, and its effectiveness depends on proper proportions.

    Pure Substances

    • To determine if a substance is pure, look for its density, color, and boiling point in a standard reference table.
    • Certain substances decompose when heated, which can affect their boiling point.

    Fluid Flow

    • The flow rate of a fluid depends on its viscosity and temperature.
    • Increasing the temperature of a fluid can decrease its viscosity, making it flow faster.
    • Windshield washer fluid is a solution that needs to be designed for winter conditions, considering its melting point.

    Drag and Viscosity

    • The drag exerted on objects moving through air is caused by air molecules colliding with the object.
    • The shape of an object affects the drag it experiences, with some shapes experiencing more drag than others.
    • Viscosity is the measure of a fluid's resistance to flow, and it can be affected by temperature and pressure.

    Buoyancy

    • Buoyancy is the upward force exerted on an object by a fluid, such as water or air.
    • The buoyant force depends on the density of the fluid and the volume of the object.
    • Objects experience less weight when submerged in a fluid due to the buoyant force.

    Density and Buoyancy

    • Density is the mass of a substance per unit volume.
    • The density of a fluid affects the buoyant force it exerts on an object.
    • As the density of a fluid increases, the buoyant force increases.

    Applications

    • Snowshoes make it easier to walk on snow by spreading out the force over a larger area, reducing the pressure on the ground.
    • Wider, thicker tires on mountain bikes or all-terrain vehicles offer better traction or grip on the terrain.
    • The water pressure at a depth of 1 m below the water surface in a swimming pool is 10 000 Pa.

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    Description

    Test your understanding of the mix and flow of matter with this quiz, covering physical properties, behavior, and characteristics of fluids and gases. Suitable for Grade 8 students.

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